Article

Seasonal patterns of disturbance influence recruitment of the sea palm, Postelsia palmaeformis

April 1996
Journal of Experimental Marine Biology and Ecology 197(1):1-14

April 1996
197(1):1-14

Authors:

University of California, Santa Barbara

Physical disturbance can have important effects on the distribution and abundance of sessile organisms, and temporal variation in the disturbance regime may strongly influence recruitment of species which reproduce seasonally. The sea palm Postelsia palmaeformis is a kelp with an annual, heteromorphic life history that inhabits the mid-tidal zones of some of the most wave-exposed rocky intertidal areas on the Pacific coast. Postelsia is thought to thrive in wave beaten areas, since winter storms remove patches of the mussel Mytilus californianus, the dominant competitor, thereby freeing bare space on the rock. To evaluate the effects of temporal variation in the physical disturbance regime and the effects of mussels on Postelsia recruitment, small plots in a mussel bed surrounded by existing Postelsia were seasonally cleared of mussels. Sea palm recruitment occurred in all plots, but was greatest in the most recent winter mussel removal treatment, suggesting survival of microscopic or young stages of Postelsia may be enhanced beneath mussel beds during fall/winter. Postelsia's annual life history seems ideally suited to wave-exposed sites, where predictable winter disturbances remove mussels. This study shows that Mytilus can also have positive effects on Postelsia recruitment.

Multi-scale stability of an intertidal kelp ( Postelsia palmaeformis ) near its northern range edge through a period of prolonged heatwaves

Article

Oct 2023

Background and Aims Climate change, including gradual changes and extreme weather events, is driving widespread species losses and range shifts. These climatic changes are felt acutely in intertidal ecosystems, where many organisms live close to their thermal limits and experience the extremes of both marine and terrestrial environments. A recent series of multi-year heatwaves in the northeast Pacific Ocean may have impacted species even toward their cooler, northern range edges. Amongst them, the high intertidal kelp Postelsia palmaeformis, has traits that may make it particularly vulnerable to climate change, but it is critically understudied. Methods In 2021 and 2022, we replicated in-situ and aerial P. palmaeformis surveys that were originally conducted in 2006 and 2007 to assess the state of northern populations following recent heatwaves. Changes in P. palmaeformis distribution, extent, density, and morphometrics were assessed between these two time points over three spatial scales, ranging from 250-m grid cells across the entire 167-km study region, to within grid-cells, and the individual patch. Results We found evidence consistent with population stability at all three scales: P. palmaeformis remained present in all 250-m grid-cells in the study region where it was previously found, and neither extent within-cells or patch density changed significantly between time points. However, there was evidence of slight distributional expansion, increased blade lengths, and a shift to earlier reproductive timing. Conclusions We suggest that apparent long-term stability of P. palmaeformis may be due to thermal buffering near its northern range edge as well as from the wave-exposed coastlines it inhabits, which may have decreased heatwave impacts. Our results highlight the importance of multi-scale assessments when examining changes within species and populations, and the importance of dispersal capability and local conditions in regulating species’ responses to climate change.

Cryptic Processes in the Sea: A Review of Delayed Development in theMicroscopic Life Stages of Marine Macroalgae

Article

Full-text available

Jun 2006

Population consequences of biomass loss due to commercial collection of the wild seaweed Postelsia palmaeformis

Article

Full-text available

Aug 2010

Commercial take of Postelsia palmaeformis (hereafter Postelsia), an annual kelp found only on wave-exposed, rocky shores of the Northeast Pacific, is increasing rapidly in California where regulation of the edible seaweed 'fishery' is minimal. Many commercial collectors use a frond trimming method they claim is sustainable and allows for multiple collections per year. Unlike cutting at the stipe, which is lethal and can drive populations to extinction, frond trimming preserves the meristem, allowing fronds to regrow. To evaluate the ecological consequences of biomass loss and sustainability of this commercial take method we conducted 2 field experiments. We trimmed fronds at different frequencies and times and then measured: (1) frond regrowth and reproductive output and (2) population recruitment. We explored the potential for geographic variation by replicating the first experiment near the center and southern limit of Postelsia's biogeographic range. Fronds trimmed in April-June were able to regrow and eventually produce viable spores, albeit at somewhat reduced rates. However, spore production was sharply reduced when fronds were trimmed after the onset of sporogenesis (end of July), whether trimmed once or twice. These effects were similar across the geographic range examined but varied in magnitude. Recruitment was 38% greater in populations not subjected to trimming and population sizes were reduced by 40 to 50% when trimmed. A precautionary approach to management should: (1) mandate the frond trimming method, (2) limit collection to once a year and (3) close the commercial season before the onset of reproduction.

It’s the Little Things: The Role of Microscopic Life Stages in Maintaining Kelp Populations

Article

Full-text available

Apr 2022

Matthew Edwards

Kelp forests are experiencing broad scale declines in abundance and shifts in latitudinal ranges in many areas of the world due to numerous environmental stressors, especially those associated with climate change. While the majority of studies on kelp ecology have focused exclusively on the macroscopic sporophyte life stage, a growing number of studies is showing quite convincingly that the microscopic zoospore and gametophyte life stages can be important to establishing spatial patterns in these marine forests, and in facilitating their recovery following deforestation. Unfortunately, their microscopic sizes have made them difficult to study in the field, leading to a ‘black box’ surrounding what we know about their ecologies. However, advances in experimental methodologies and a growing number of laboratories studying kelp microscopic life stages are revealing how they are affected by variability in environmental conditions, and are providing a clearer picture of how kelp forests might respond to a changing ocean climate. These studies have largely revealed that kelps can disperse over a wide range of distances, enhanced by the synchronous release and vertical transport of zoospores into shallower water, and by floating rafts of reproductive thalli. Settlement on the benthos is facilitated by both positive and negative chemotaxis, and by active selection of microhabitats that favor their growth and survival. Following settlement and subsequent germination, the haploid gametophytes can delay their development and form a bank of microscopic forms that persist during periods that are unfavorable for the large sporophyte populations, or they can develop and undergo sexual reproduction during which they respond to variability in environmental conditions. In particular, they are strongly affected by increases in irradiance (PAR, UVA + UVB) and temperature, decreases in nutrients and salinity, and by sedimentation and grazing. However, the manner in which they respond to these stressors varies among species and with their geographic distributions, which is integral to establishing biogeographic patterns in the large sporophyte populations. Given these factors are expected to change as the ocean climate changes, these species-specific responses have significant implications for future patterns of distribution and abundance of these iconic marine forests.

Cancer Community Ecology

Article

Full-text available

Sep 2020

Here we advocate Cancer Community Ecology as a valuable focus of study in Cancer Biology. We hypothesize that the heterogeneity and characteristics of cancer cells within tumors should vary systematically in space and time and that cancer cells form local ecological communities within tumors. These communities possess limited numbers of species determined by local conditions, with each species in a community possessing predictable traits that enable them to cope with their particular environment and coexist with each other. We start with a discussion of concepts and assumptions that ecologists use to study closely related species. We then discuss the competitive exclusion principle as a means for knowing when two species should not coexist, and as an opening towards understanding how they can. We present the five major categories of mechanisms of coexistence that operate in nature and suggest that the same mechanisms apply towards understanding the diversification and coexistence of cancer cell species. They are: Food-Safety Tradeoffs, Diet Choice, Habitat Selection, Variance Partitioning, and Competition-Colonization Tradeoffs. For each mechanism, we discuss how it works in nature, how it might work in cancers, and its implications for therapy.

The influence of ocean warming on the provision of biogenic habitat by kelp species

Thesis

Nov 2018

Harry Teagle

Kelp forests represent some of the most productive and diverse habitats on Earth, and play a critical role in structuring nearshore temperate and subpolar environments. They have an important role in nutrient cycling, energy capture and transfer, and offer biogenic coastal defence. Kelps also provide extensive substrata for colonising organisms, ameliorate conditions for understorey assemblages, and generate three-dimensional habitat structure for a vast array of marine plants and animals, including a number of ecologically and commercially important species. This thesis aimed to describe the role of temperature on the functioning of kelp forests as biogenic habitat formers, predominantly via the substitution of cold water kelp species by warm water kelp species, or through the reduction in density of dominant habitat forming kelp due to predicted increases in seawater temperature. The work comprised three main components; (1) a broad scale study into the environmental drivers (including sea water temperature) of variability in holdfast assemblages of the dominant habitat forming kelp in the UK, Laminaria hyperborea, (2) a comparison of the warm water kelp Laminaria ochroleuca and the cold water kelp L. hyperborea as habitat forming species, and further investigation into the impacts of this subtle climate driven substitution of habitat forming kelps, and (3) experimental manipulation of densities of the dominant intertidal kelp in the UK, Laminaria digitata, in order to understand the impacts of climate driven loss of a dominant habitat forming species. L. hyperborea assemblages varied significantly between study regions spanning ~9° of latitude, as well as between and within sites at a local scale. Patterns in mobile and sessile assemblage structure were driven principally by different environmental factors. Overall patterns in the structure of biogenic habitat and assemblage structure did not vary predictably with latitude, indicating that other processes acting across multiple spatial scales are important drivers of assemblage structure. L. ochroleuca hosted impoverished assemblages associated with both holdfasts and stipes, compared with L. hyperborea. Further, climate driven increases in the relative abundance of L. ochroleuca relative to L. hyperborea lead to disruption of an important habitat cascade associated with the stipe of L. hyperborea and epiphytic algae. L. ochroleuca stipes typically lack the dense epiphytic assemblage associated with L. hyperborea, and host depauperate faunal assemblages which may have impacts on higher trophic levels. Experimental reduction in the density of L. digitata led to a dramatic shift in dominance from perennial to annual species, particularly the pseudo-kelp Saccorhiza polyschides on an exposed rocky shore. Impacts on a sheltered shore were subtler, and may have been tempered by the presence of another perennial kelp, Saccharina latissima. Loss of L. digitata led to a reduction in the standing stock of macroalgae after ~2.5 years of manipulation on both shores. These findings have significant implications for the structure and functioning of rocky shores in the future. Overall, anthropogenic climate change is likely to negatively impact the functioning of kelp forests as repositories of biodiversity in the future via the reshuffling of warm- and cold-water kelp species and through an overall loss of algal biomass and associated habitat due to continued increases in seawater temperature in the northeast Atlantic.

The role of kelp species as biogenic habitat formers in coastal marine ecosystems

Article

Feb 2017
J EXP MAR BIOL ECOL

Kelps are ecologically important primary producers and ecosystem engineers, and play a central role in structuring nearshore temperate habitats. They play an important role in nutrient cycling, energy capture and transfer, and provide biogenic coastal defence. Kelps also provide extensive substrata for colonising organisms, ameliorate conditions for understorey assemblages, and provide three-dimensional habitat structure for a vast array of marine plants and animals, including a number of commercially important species. Here, we review and synthesize existing knowledge on the functioning of kelp species as biogenic habitat providers. We examine biodiversity patterns associated with kelp holdfasts, stipes and blades, as well as the wider understorey habitat, and search for generality between kelp species and biogeographic regions. Environmental factors influencing biogenic habitat provision and the structure of associated assemblages are considered, as are current threats to kelp-dominated ecosystems. Despite considerable variability between species and regions, kelps are key habitat-forming species that support elevated levels of biodiversity, diverse and abundant assemblages and facilitate trophic linkages. Enhanced appreciation and better management of kelp forests are vital for ensuring sustainability of ecological goods and services derived from temperate marine ecosystems.

The Role of Alternate Life-History Stages of a Marine Macroalga: A Seed Bank Analogue?

Article

Sep 2000

Matthew Edwards

Many organisms occurring in temporally variable environments have evolved life-history traits that enable their populations to persist during unfavorable environmental conditions. Numerous terrestrial plants, insects, and marine invertebrates, for example, rely on resting stages that disperse their propagules in time. Although widely observed among many taxa, few examples exist for marine macroalgae, at least in part because of the methodology involved in studying them. Here, I determined that microscopic life stages of the annual marine macroalga Desmarestia ligulata overwinter during periods when the macroscopic thalli are absent, thereby allowing this species to persist in temporally variable environments. Examination of field-grown microscopic stages with fluorescence microscopy identified these stages as gametophytes. Holdfast tagging experiments determined that re- cruitment of the macroscopic stages was not enhanced by regrowth of perennial thalli as observed in other macroalgae, suggesting that overwintering gametophytes were the sole source of sporophyte recruitment. In contrast to true resting stages, Desmarestia gameto- phytes were not dormant, but rather were metabolically active, sensitive to small differences in environmental quality, and highly subject to physical damage. Gametophyte photosyn- thetic rates were greater under higher irradiance, and growth rates were greater under longer photoperiods and higher irradiance. Although their survival appeared to be reduced by grazing from large (.1 cm) invertebrates and sedimentation, gametophytes were able to survive in the field for at least 15 mo and thereby enhance sporophyte recruitment more than a year after settlement. I suggest that Desmarestia gametophytes be regarded as al- ternate life-history stages that simply maintain populations under a different set of envi- ronmental conditions than the macroscopic sporophytes do, rather than as ''dormant'' or ''resting'' stages.

Colonisation of newly-opened habitat by a pioneer species, Alvinella pompejana (Polychaeta: Alvinellidae), at East Pacific Rise vent sites

Article

Full-text available

Nov 2005
MAR ECOL-PROG SER

Animal communities on the walls of deep-sea hydrothermal chimneys are distributed in mosaics of patches that may evolve as local environmental conditions change and biological interactions develop. Alvinella pompejana Desbruyeres et Laubier, 1980 is one of the first metazoan colonisers of new surfaces created by mineral precipitation, and therefore may be particularly important in community establishment in active parts of smokers. Here our goal was to investigate the colonisation mechanisms of A. pompejana in new patches and determine whether these mechanisms may influence population structure and reproductive patterns in this species. We deployed a series of TRAC (Titanium Ring for Alvinellid Colonisation) devices at East Pacific Rise (EPR) vent sites to compare the size and stage (i.e. reproductive maturity) distribution of A. pompejana individuals between recently colonised patches (TRACs) and established patches (grabbed by submersible). TRACs deployed for short time periods (11 d to 1 mo) were generally colonised by smaller individuals than those found in background populations or in TRACs deployed for longer time periods (> 1 mo). Colonists into new patches were a mix of juveniles and individuals that were sexually mature but non-reproductive (i.e. not producing gametes), whereas background population and older patches harboured a mixture of individuals at different stages including reproductive females. Although some individuals may have recruited on TRACs as larvae, the major colonisation process involved was probably immigration of post-larval stages. In long-term TRAC, reproductive females were not reproductively synchronised. In this dynamic environment, reproduction would be triggered by the disturbance/migration processes, explaining the heterogeneity observed in reproductive patterns.

A multispecies laboratory assessment of rapid sporophyte recruitment from delayed kelp gametophytes

Article

Mar 2011
J PHYCOL

Laura T. Carney

Recent work suggests that the ability to delay reproduction as resistant haploid gametophytes may be important for seaweeds that experience unpredictable disturbances or seasonal periods of poor conditions that result in adult sporophyte absence. Further, delayed gametophytes of some kelp species (order Laminariales) may produce sporophytes more rapidly than if they had never experienced a delay, conferring a competitive advantage when conditions improve or after disturbance events. Here, it was determined that the gametophytes of the canopy-forming kelp Macrocystis pyrifera (L.) C. Agardh could delay reproduction in a one- to two-cell state (<50 μm) for at least 7 months when grown under nutrient-limiting conditions. These stages retained reproductive viability and produced sporophytes within 5 d once nutrients were increased. This finding suggests that gametophytes could potentially promote recovery of M. pyrifera populations after extended periods of sporophyte absence. In addition, the time required for sporophyte production between gametophytes of the four most conspicuous kelp species in Southern California that had delayed reproduction and gametophytes that had not was compared. For these four kelp species, a delay of at least 30 d conferred a 40%–76% reduction in the time required for sporophyte production once nutrients were received. Fecundity did not decrease with delay duration, suggesting there is no apparent cost of delayed development for kelps as has been observed in other organisms. Thus, delayed development may be a viable strategy for surviving and initially dominating in environments with variable quality.

Diversity and Functioning of Harbor Communities. Influence on Non Indigenous Species in a Climate Change Driven Context

Thesis

Dec 2021

Robin P. M. Gauff

Marine infrastructures offer new substrates, colonized by a variety of organisms (biofouling), but are different from natural habitats since environmental filters and ecological processes differ, biotic composition differs from natural habitats, and they are characterized by a high diversity and abundance of non-indigenous species (NIS). Artificialization in marinas modifies hydrodynamism, affecting the water column characteristics like temperature and favoring the concentration of anthropic disturbances like pollutants. Environmental gradients may be present, with higher levels of disturbance in the innermost parts of marinas, acting as selective filters for organisms. The present work aimed to understand the diversity and functioning of sessile communities in marinas by studying how disturbance gradients shape community structure and function between the entrances of marinas and their more disturbed inner parts. A particular focus laid on NIS, which are common in marinas and constitute an important societal challenge. An experimental approach (reciprocal transplant) in six marinas from two regions (Mediterranean, Atlantic), revealed that differences in community structure are caused by local pollution levels, associated to local adaptation at small spatial scale (<100m). However, other processes might affect these dynamics like biotic interactions (predation) and pulse disturbances (heat waves). In the context of climate change, we also tested how projected seawater warming (+3°C) may impact marina communities and might favor NIS. These results might help understanding how disturbances in marine urban ecosystems drive biodiversity and especially the prevalence of NIS.

Intertidal ecology of northern Portuguese rocky shores

Thesis

Jan 2000

António Emílio Ferrand De Almeida Múrias Dos Santos

p>Abundance and zonation of species were described for northern Portuguese rocky shores. All shores displayed exposed or moderately exposed zonation patterns, with mussels and barnacles dominating the eulittoral zone. Differences between the northern and southern coast were mainly observed at the lower shore level. Several southern limits of cold-water species of brown macroalgae were observed in this region. Northern shores formed a distinct group within the Portuguese coast and were similar to those found on the northern coast of Spain, French Brittany and southwest coast of the United Kingdom. The dynamics of midshore mussel assemblages was investigated at several spatial and temporal scales. A model was put forward, using wave action as the main factor driving the variation of mussel occupancy through time. Percentage cover of mussels, barnacles and free space were highly variable through time. Mussels did not display any seasonal patterns at the shore or site scales. Conversely, the percentage cover of barnacles decreased significantly during the winter, whilst free space increased after it. The proposed model as rejected, and a new model was developed based on the evidence gathered. The new model predicted that gains and losses in area would be similar within each season but higher during the winter. Moreover, losses in the winter would be compensated by growth of mussels on top of barnacles. The effects of an oil spill on mussel percentage cover and limpet density were assessed through the use of beyond BACI analyses. No effects were detected, either on mussels or limpets, most probably because the variability caused by the oil spill was within the natural range of variability of these populations.</p

El Niño and marine heatwaves: Ecological impacts on Oregon rocky intertidal kelp communities at local to regional scales

Article

Full-text available

Mar 2022
ECOL MONOGR

El Niños and marine heatwaves (MHWs) are predicted to increase in frequency under greenhouse warming. The impact of climate oscillations like El Niño‐Southern Oscillation on coastal environments in the short term likely mimics those of climate change in the long term; therefore, El Niños may serve as a short‐term proxy for possible long‐term ecological responses to an increasingly variable climate. Understanding and prediction of ecosystem responses requires elucidating the mechanisms underlying different organizational scales (organism, space, and time). We analyzed spatiotemporal variation in the effect of the 2015–2016 El Niño and the overlapping 2014–2016 East Pacific MHW on three intertidal kelps (Hedophyllum sessile, Egregia menziesii, and Postelsia palmaeformis) at seven sites across 300 km of the Oregon coast and over three years post El Niño. We measured percent cover, density, maximum length, growth, and carbon : nitrogen (C:N) ratios monthly in spring/summer at each site from 2016 through 2018. Results revealed a complex interplay between spatial, temporal, and biological factors that modified the effects of these thermal anomalies on Oregon intertidal kelp populations. Our findings generally agree with prior literature showing detrimental effects of El Niño on kelp. However, El Niño and possibly MHW effects can be mitigated or amplified by environmental processes and kelp life history strategies. In our study, coastal upwelling provided regional relief for the kelp individuals with respect to their growth needs and mitigated the adverse effects of warming. On the other hand, we also found that coastal upwelling amplified, or compounded, detrimental effects of El Niño by increasing phytoplankton‐induced shading and mollusk grazing on juvenile and adult kelps, thereby reducing their density. Given the greater uncertainty associated with warming events and climate change in the California Current Upwelling System and its biological implications, our findings reiterate the importance of acquiring better understanding of how context‐specific underlying conditions modify ecosystem processes. More specifically, understanding how demographic traits and life history stages of kelp change with biological interactions and environmental forcing over temporal and spatial scales is crucial to anticipating future climate change ramifications.

Kelp Morphology and Herbivory Are Maintained Across Latitude Despite Geographic Shift in Kelp-Wounding Herbivores

Article

Sep 2021

Herbivores can drastically alter the morphology of macroalgae by directly consuming tissue and by inflicting structural wounds. Wounds can result in large amounts of tissue breaking away from macroalgae, amplifying the damage initially caused by herbivores. Herbivores that commonly wound macroalgae often occur over only a portion of a macro-alga's lifespan or geographic range. However, we know little about the influence of these periodic or regional occurrences of herbivores on the large-scale seasonal and geographical patterns of macroalgal morphology. We used the intertidal kelp Egregia menziesii to investigate how the kelp's morphology and the prevalence of two prominent kelp-wounding her-bivores (limpets and amphipods) changed over two seasons (spring and summer) and over the northern extent of the kelp's geographic range (six sites from central California to northern Washington). Wounds from limpets and amphipods often result in the kelp's fronds being pruned (intercalary meristem broken away), so we quantified kelp size (combined length of all fronds) and pruning (proportion of broken fronds). We found similar results in each season: herbivores were most likely to occur on large, pruned kelp regardless of site; and limpets were the dominant herbivore at southern sites, while amphipods were dominant at northern sites. Despite the geographic shift in the dominant herbivore, kelp had similar levels of total herbivore prevalence (limpets and/or amphipods) and similar morphologies across sites. Our results suggest that large-scale geographic similarities in macroalgal wounding, despite regional variation in the herbivore community, can maintain similar macroalgal morphologies over large geographic areas.

EIGHTEEN. Intertidal

Chapter

Dec 2019

Recovery ability of lowshore sessile assemblages in a highly contaminated post-industrial area

Article

Jan 2020
MAR ENVIRON RES

The inheritance of environmental contamination left by abandoned industrial plants is widespread globally. Here we compared the patterns of recovery of lowshore algal and invertebrate assemblages between the post-industrial site of Bagnoli-Coroglio and four reference sites distributed along the coast in the Gulf of Naples, southern Tyrrhenian Sea. The structure of whole assemblages, richness of taxa and abundance of individual taxa were followed during one year since an event of experimental disturbance consisting in the removal of all erect organisms from the rocky substrate. Our main findings suggest that the examined benthic assemblages recovered effectively and quickly after a pulse disturbance and, contrarily to initial expectations, that this ability was comparable between the post-industrial site and the reference sites. This result is discussed in terms of several plausible processes and mechanisms, including the general capability of intertidal organisms to recover from physical disturbance, the potential high level of environmental stress affecting the reference sites too, the chance that the most intense impacts of contamination remained restricted to the sediments of the post-industrial site without propagating to adjacent rocky habitats, and the large natural variability of reference sites that may have masked weak effects of the historical contamination. Irrespective of the actual causes, we emphasize the need for including natural variability of the examined system in any future restoration interventions, to guarantee representation of the range of variation of target organisms and of their underlying processes, and to avoid confounding the intended post-industrial impact with the effects of other natural and anthropogenic processes.

Assessing the performance of artificial reefs as substitute habitat for temperate reef fishes: Implications for reef design and placement

Article

Mar 2019

Artificial reefs (ARs) have been advocated and implemented as management tools for recreational fisheries, species conservation and habitat replacement. For ARs to function as substitute habitat for degraded natural reefs, they should perform as close as possible to local natural reefs, however this is seldom investigated. Here we evaluated the performance of new custom-designed reef structures (CDARs) as fish habitat. As a benchmark for their success, we compared fish abundance, diversity and community composition on CDARs to another commonly used AR type (Reef Balls (RBs)) and nearby natural reefs. Fish were monitored on all reef types over two recruitment seasons at three locations in Port Phillip Bay, Australia. Overall, there were no consistent differences in fish density among reef types, although densities on both AR designs were markedly lower than natural reefs at some locations. However, fish species richness on the CDARs was, on average, 2× higher than natural or RB reefs. There were large dissimilarities in fish community composition among reef types across all locations and years. These dissimilarities declined over time with the CDARs becoming more similar to natural communities than to RB reefs. Our results suggest that CDARs can play a role in reef fish conservation where natural reefs are under threat, supporting natural community structure and enhancing local biodiversity. Overall, our findings suggest that location of deployment, rather than design, has a more significant influence on fish abundances on ARs, whereas reef design is an important determinant of species diversity and community structure irrespective of location. ARs represent an important management tool for enhancing fisheries productivity and conservation in areas where reef habitat has been degraded or lost. However, failure to incorporate consideration of reef location and design into future AR deployments may lead to poor performance and failure to achieve restoration or conservation goals.

Factors influencing recruitment and appearance of bull kelp, Nereocystis luetkeana (phylum Ochrophyta)

Article

Dec 2018

The dynamics of annual species are strongly tied to their capacity for recruitment each year. We examined how competition and propagule availability influence recruitment and appearance and tracked survivorship of an annual species of marine macroalgae, the bull kelp (Nereocystis luetkeana), which serves as major biogenic habitat in the Salish Sea of Washington State. We hypothesized that (i) juvenile N. luetkeana would exhibit a seasonal appearance as a cohort in the spring and (ii) competition for space would be more limiting than propagules (spores) to recruitment at sites adjacent to established N. luetkeana beds. We tagged N. luetkeana recruits in the field to track appearance and survivorship across seasons (spring, summer, fall, and winter), using a two‐factor crossed design to assess effects of competition and propagule availability on appearance of new N. luetkeana sporophytes. Survivorship of N. luetkeana recruits was low and, whereas most new individuals arose in the spring, some appeared in every season. New N. luetkeana recruits also appeared the earliest (median 8 weeks vs. >20 weeks) after experimental “seeding” in the spring as compared to other seasons. Eliminating macroalgal competitors (“clearing”) influenced the appearance of recruits more than enhancement of propagules in the spring. An improved understanding of factors regulating the seasonal appearance of new N. luetkeana sporophytes furthers our understanding of this crucial foundation species' appearance and persistence across seasons, which is increasingly important as global ocean conditions change, and highlights the importance of studying organisms with complex life histories across multiple stages and geographical regions.

Marine Macroalgae: Prospective Hitchhikers of Ship Ballast

Article

Full-text available

Sep 2018

Temjensangba Imchen

Invasive alien species, on successful establishment, can displace native species. The threat of invasive species arises in view of their ability to outcompete and destabilize native biodiversity. Invasive species are found across all taxonomic groups of plants, animals and microorganisms. The green macroalga Ulva flexuosa has a potential to become invasive and this species was investigated for its hitchhiking potential under laboratory conditions. Zoospores of U. flexuosa were maintained at 4°C for nearly 10 months in the dark. Recruitment potential of zoospores after dark stress was tested in a modified Provasoli medium under optimal laboratory conditions. The success rate of zoospore recruitment was 61%. The paper describes the transfer potential through shipping activities by correlating the Ulva zoospores recruitment potential and survivability.

Population dynamics of temperate kelp forests near their low-latitude limit

Article

Feb 2017
AQUAT BOT

Effects of ocean acidification, temperature and copper on the development of early life stages of the native kelp Macrocystis pyrifera and the invasive kelp Undaria pinnatifida from Southern New Zealand

Thesis

Full-text available

Oct 2016

Pablo Leal

Anthropogenic activities have increased atmospheric CO2 concentrations from pre-industrial concentrations of 280 ppm to current values of 400 ppm. These atmospheric emissions of CO2 are responsible for the ongoing increase in seawater temperature and the reduction of pH in the ocean’ surface, phenomena known as ocean warming (OW) and ocean acidification (OA), respectively. Model-based projections indicate that the global ocean surface temperature will increase by 4°C whereas the pH will decrease from a current 8.10 to 7.74 by 2100. However, these two global events are not occurring in isolation because anthropogenic activities also threatens coastal environments at local levels. For instance, in coastal environments, natural concentrations of copper are low but are increasing due to human industrialization. In addition, the speciation and bioavailability of copper in seawater is highly dependent on seawater chemistry. Therefore, reductions in seawater pH due to OA will increase the toxic, free ionic form of copper in oceans by 20% by the end of the current century. These abiotic changes can have important impacts on marine biota and ecosystems. Fleshy (non-calcifying) macroalgae such as those that belong to the Order Laminariales are important components of coastal environments. Macroalgae, as sessile organisms, are exposed to constant changes in abiotic factors and the community dynamics (e.g., growth and reproduction) depend on their tolerance to stress. Despite their importance, few studies have focused on the effects of OW, OA and/or copper pollution on fleshy macroalgae and even less have focused on their early life stages. Early life stages have been reported to be the most sensitive phase of the macroalgal life cycle to stressors. Therefore, the main purpose of this work was to evaluate the separate and interactive effects of seawater temperature, pH and copper concentration on the development of microscopic stages of the native kelp M. pyrifera and the invasive kelp U. pinnatifida from southern New Zealand. The first result of this work was that, in M. pyrifera, sporogenesis occurred in basal sporophylls (specialized reproductive laminae) as well as in non-reproductive laminae such as pneumatocyst-bearing adult blade and young apical scimitars. The sorus surface area was greater on sporophylls (57%) than in adult blades and young scimitars (25%). Meiospore release was greater in apical scimitars, followed by adult blades and sporophylls. However, germination of meiospores from different laminae was not significantly different, indicating that meiospores produced in all types of fertile laminae were equally viable. The first climate change-related experiment consisted of monitoring meiospore development of M. pyrifera and U. pinnatifida cultured under four seawater pH treatments (pH 7.20, extreme OA predicted for 2300; pH 7.65, OA predicted for 2100; pH 8.01, ambient pH; and pH 8.40, pre-industrial pH) for 15 days. Reduced seawater pH (7.20 and 7.65) had no effects on meiospore germination but had positive effects on germling growth rates and gametophyte size of both species compared to higher pH (8.01 and 8.40). Gametophyte sex ratio was biased towards females under all pH treatments. Germling growth rate under OA was significantly higher in M. pyrifera compared to U. pinnatifida but gametophyte development was equal for both kelps under all seawater pH treatments, indicating that the microscopic stages of the native M. pyrifera and the invasive U. pinnatifida will respond similarly to OA. The second experiment climate change-related experiment consisted of monitoring meiospore development of M. pyrifera and U. pinnatifida cultured under four seawater pH treatments (pH 7.20, 7.65, 8.03, and 8.40) and two temperature treatments (12°C, ambient temperature; and 16°C, OW predicted for 2100) for 15 days. Reduced seawater pH and elevated temperature had no effects on meiospore development and positive effects on germling growth rates and gametophyte size of both species compared to higher pH (8.01 and 8.40) and lower temperature (12°C), whereas gametophyte sex ratio was not affected by the interaction between the two factors. Despite some small differences between species, results of this experiment suggest that microscopic stages of the native M. pyrifera and the invasive U. pinnatifida will respond similarly to OA and OW. The single effects of the local stressor, copper pollution, on the development of M. pyrifera and U. pinnatifida meiospore were examined. After settlement, meiospores of both kelps were exposed to five nominal copper treatments (control, 100, 200, 300 and 400 µg L-1 Cu) for 9 days. Analyses of total dissolved copper (CuT) concentrations in the blanks showed that nominal copper concentrations were reduced to 54, 91, 131 and 171 µg L-1 CuT (i.e., > 50% of the CuT was adsorbed onto the culture vessel walls). In the media with meiospores, the CuT also decreased: to 39, 86, 97 and 148 µg L-1 CuT in M. pyrifera, and to 39, 65, 97 and 146 µg L-1 CuT in U. pinnatifida (i.e., 6 – 15% of the dissolved copper was adsorbed by the cells). Meiospore germination decreased with increasing copper concentrations but gametogenesis was arrested under all copper treatments. The effective copper concentration causing 50% of arrested germination (Cu EC50) was higher for U. pinnatifida (231 µg L-1 CuT) than for M. pyrifera (157 µg L-1 CuT), suggesting ecological success for the invasive species in copper polluted environments; however, the subsequent inhibition of gametogenesis under all copper treatments indicated no difference in copper tolerance between both kelp early life stages. The reduction of CuT during the previous experiment occurred because copper might be adsorbed onto glass and/or plastic and this can be avoided using a proper trace metal clean procedure. Therefore, a review on the methodologies used in the literature on copper ecotoxicology of marine macro- and microalgae, specifically the use of trace metal clean procedures such as the labware used (glassware vs plasticware), methods of cleaning the labware (acid soaking and ultrapure water rinsing), stock solution preparation (copper source and acidification), and measurement and reporting of dissolved copper concentrations was performed. The main results of this review were that 50% of the articles did not specify the laboratory–ware, 25% used glassware and 25% plasticware; only ~30% of the studies specified cleaning protocols for labware to remove trace metal impurities; the copper form used to prepare the stock solutions was specified in ~80% of studies but acidification to stabilize the dissolved copper was performed in only ~20%; and the dissolved copper concentration was measured in only ~30% of studies. Based on these finding, a trace metal procedure was recommended for conducting copper ecotoxicological studies. A four-factor experiment was performed to investigate the interactive effects of OA, OW and copper pollution on the meiospore development of M. pyrifera and U. pinnatifida. Meiospores of both species were cultured under two seawater pH treatments (7.65 and 8.16), and two temperature treatments (12 and 16°C), and to the species-specific Cu-EC50 for 18 days. In both species, meiospore germination and germling growth rates significantly decreased in the copper treatment, irrespective of pH and temperature whereas gametophyte development for both species was inhibited by copper in all pH and temperature treatments. These results suggest that a local stressor (e.g., copper) is more important to the development of microscopic stages of M. pyrifera and U. pinnatifida than global climate change factors. In summary, results of this study indicate that meiospore development of M. pyrifera and U. pinnatifida will be able to tolerate future OA and OW. That tolerance might be related to: 1) macro- and microscopic stages of both kelps being able to use HCO3- and CO2 to support photosynthesis, therefore, the higher CO2(aq) availability due to OA (pH 7.20 to 7.65) will not affect their physiology; and 2) both M. pyrifera and U. pinnatifida have a wide temperature tolerance (4 to 30C°) which may allow them to perform well in a future warmer ocean (+ 4C°). In contrast, relatively high copper concentrations inhibited meiospore development of both kelp species. This finding indicates that local drivers (e.g., copper pollution) may be more important to physiological processes during meiospore development than global climate change factors. Furthermore, the responses of meiospores to the experimental abiotic factors (i.e., OA, OW and Cu) were similar between the study species, indicating that the invasive U. pinnatifida is unlikely to have an advantage over the native M. pyrifera in natural coastal environments.

Impacts and effects of ocean warming on intertidal rocky habitats

Chapter

Full-text available

Sep 2016

The influence of environment and exploitation on sex change limpets

Thesis

Oct 2013

Débora Borges

Patellid limpets are harvested around the world and many stocks are currently overexploited. This study investigated the influence of environment and harvesting upon the biology of target species (Patella spp.) and upon the macro-community structure of non-target species. A broad-scale survey of Patella spp. across the British Isles and Portugal revealed that non-exploited Patella vulgata populations from England had traits indirectly associated with protandry. Females predominated in larger size classes; cumulative frequency distributions of males and females were different; sex ratios were biased towards the first sex and smallest sizes of males were smaller than the smallest sizes of females. In Portugal, P. vulgata populations did not show these patterns, suggesting that protandry was not occurring in those P. vulgata populations, although alternative explanations include the influence of low recruitment leading to fewer small males. In the England Patella depressa appeared to be gonochorist with a sex ratio of 1:1. In Portugal, however, P. depressa also showed some patterns indicating the possibility of slight protandry. In a manipulative experiment to simulate size-selective harvesting of limpets by humans, changes in sex ratio of P. vulgata in the south-west of England were monitored over an 18-month period of repeated removal of bigger limpets. There was strong evidence that the size at sex change decreased in response to the exploitation treatment, emphasizing its plasticity. Sex change occurred at a bigger size than expected from the overlap in male and female size classes. The limpet exploitation led to establishment of Fucus spp. At the end of the experiment, control plots had lower percentage cover of Fucus spp. than both low- and high-exploitation plots. Univariate and multivariate analyses confirmed that the communities on the two shores responded differently to the same source of disturbance. A comparative survey of populations across a gradient of exploitation in the Canary Islands indicated that the abundance of Patella aspera decreased from 1992 to 1999, while for Patella candei crenata no differences were detected, suggesting that P. aspera was under a higher harvest pressure during that period. The observed differences in catches between islands in 1999 indicated that overexploitation of limpet stocks at that time was not yet evident. The results of the field surveys and the manipulative experiment are discussed with respect to the role of ecological experimentation and aquaculture in resource management, and suggestions are made for key issues in future research and conservation.

Economic and Social Considerations for Wave Energy Development in California

Technical Report

Full-text available

Oct 2008

Steven C Hackett

The prospect of climate change due to anthropogenic greenhouse‐gas emissions is stimulating regulatory policies, such as California’s Global Warming Solutions Act, that will create enhanced market opportunities for electricity generated from renewable sources. Electricity from wave energy conversion has the potential to be cost‐competitive with on‐shore wind technology. Wave energy conversion facilities developed at commercial or regional scales will have a variety of economic and social impacts. This chapter begins by summarizing existing knowledge from various technical reports and published studies on the economic and social aspects of important marine uses in California. Usage information is summarized for high traffic areas, areas of importance for recreational, cultural, and economic reasons. The potential economic benefits of wave energy conversion are characterized, and summary information is provided on the economic contribution provided by commercial and recreational fisheries, coastal and marine recreation and tourism, and ports and harbors. A review of this information indicates significant gaps in our understanding of key economic and social tradeoffs involved with implementing wave energy conversion on a commercial or regional scale. Among the most important priority recommendations for future research is to produce higher‐resolution spatial data that connects coastal marine locations to the economic and other benefits they provide for users, local communities, or others, and to compile this information in a GIS map format. This information (along with a better understanding of social impacts) can then be compared to the benefits provided by wave energy conversion so that policy makers and the public can make informed decisions regarding implementation of this new form of energy generation.

Patterns of recovery of intertidal organisms after compounded anthropogenic disturbances

Article

Full-text available

Mar 2015

Coastal habitats are exposed to increasing human and natural disturbances, including extraction of organisms and extreme climatic events. Patterns of recovery (i.e. convergence towards an unmanipulated control) of the structure of benthic assemblages, the total number, and the abundance of individual taxa were examined over a period of 15 mo after the end of a previous experiment. In that experiment, crossed manipulations of levels of mussel harvesting and of the temporal patterns of storm-related mechanical disturbance (in terms of changes in variance but not in the overall intensity) were performed on north Portugal rocky shores. Effects of past disturbances were mostly detected at 3 and 9 mo after the end of disturbances, while no significant differences between unmanipulated and treated assemblages were present after 15 mo. These findings confirm that intertidal assemblages subjected to even extreme combinations of past disturbances can recover in a relatively short time. Important effects present after 3 to 9 mo were associated with the timing of disturbance, likely depending on interactions with life-history traits such as peaks in reproduction and recruitment. Contrary to theories considering disturbances as opportunities for some organisms to replace competitors that dominate space in undisturbed conditions, we observed changes in the abundances of the same taxa rather than their replacement. The present evidence contributes to the understanding of how multiple anthropogenic pressures affect the ability of intertidal assemblages to recover after disturbance.

Recruitment patterns in the Mediterranean deep‑water alga Cystoseira zosteroides

Article

Full-text available

Apr 2015
MAR BIOL

Although recruitment is considered an essential process regulating populations of many marine species, there is still a lack of knowledge about the ultimate factors that influence it. This is especially true for seaweeds, where population dynamics studies are also lacking. The main objective of this study was to investigate the main mechanisms driving the recruitment patterns of an emblematic deep-water alga in the NW Mediterranean, Cystoseria zosteroides, and its influence on their population dynamics. Five C. zosteroides populations were monitored annually at different sites along the coast of Spain by using permanent transects over three to four years. Some of these populations suffered mass mortality events from natural or anthropogenic disturbances, allowing us to study the influence of such events. Our findings agreed with the expected results for a long-lived species. Under low frequency of disturbances, C. zosteroides populations displayed few fluctuations over time given the longevity of the adults, and they were poorly influenced by the dynamics of early life stages because of negative density-dependent control of conspecifics. Moreover, disturbances had a great influence on population dynamics because the removal of adults decreased the effects of density-dependent processes, and enhanced the recruitment. Nonetheless, a high mortality was found for early life stages (~50% yr-1), contrasting with the high survival of adults (~90% yr-1). This study confirmed the slow population dynamics of these deep assemblages, demonstrated the influence of density in the C. zosteroides population dynamics and highlighted their vulnerability to the increase of natural and human-induced disturbances.

Recruitment patterns in the Mediterranean deep‑water alga Cystoseira zosteroides

Article

Full-text available

Apr 2015

Although recruitment is considered an essential process regulating populations of many marine species, there is still a lack of knowledge about the ultimate factors that influence it. This is especially true for seaweeds, where population dynamics studies are also lacking. The main objective of this study was to investigate the main mechanisms driving the recruitment patterns of an emblematic deep-water alga in the NW Mediterranean, Cystoseira zosteroides, and its influence on their population dynamics. Five C. zosteroides populations were monitored annually at different sites along the coast of Spain by using permanent transects over 3–4 years. Some of these populations suffered mass mortality events from natural or anthropogenic disturbances, allowing us to study the influence of such events. Our findings agreed with the expected results for a long-lived species. Under low frequency of disturbances, C. zosteroides populations displayed few fluctuations over time given the longevity of the adults, and they were poorly influenced by the dynamics of early life stages because of negative density-dependent control of conspecifics. Moreover, disturbances had a great influence on population dynamics because the removal of adults decreased the effects of density-dependent processes and enhanced the recruitment. Nonetheless, a high mortality was found forearly life stages (~50 % year−1), contrasting with the high survival of adults (~90 % year−1). This study confirmed the slow population dynamics of these deep assemblages, demonstrated the influence of density in the C. zosteroides population dynamics and highlighted their vulnerability to the increase in natural and human-induced disturbances.

Dinámica poblacional de Eisenia arborea Areschoug (Laminariales: Ochrophyta) en el intermareal de Punta Eugenia, Baja California Sur, México

Article

Full-text available

Jan 2009

Population dynamics of Eisenia arborea Areschoug (Laminariales: Ochrophyta) in the intertidal of Punta Eugenia, Baja California Sur, México. The population dynamics of Eisenia arborea from the intertidal zone of Punta Eugenia, Baja California Sur, was studied. Eisenia arborea is one of the critical species for the community assemblage in the study area. Sampling was carried out from December 2003 to August 2004. We measured the plant density, growth rate, reproductive season, recruitment and morphometric correlations in the population. Average density was 23 plants m-2, with a significantly maximum in July 2004. The growth rate is seasonal and, in contrast to the finding for other species from Laminariales, the growth rate for E. arborea was much lower. The average was always lower than 0.20 mm d-1. Nevertheless, younger plants showed significant higher growth rates. We found a significant seasonal variation for sori presence. The highest percentage of plants with reproductive fronds was obtained during autumn-winter. The highest number of recruits in the study site was in February 2004. Morphometric correlations between maximum stipe length and perimeter showed a positive trend. This study focuses on the most accesible portion of E. arborea populations. Such marginal parts would be the first ones to be affected by the commercial exploitation, activity that already started.

Developing Wave Energy in Coastal California: Potential Socio-Economic and Environmental Effects

Book

Full-text available

Oct 2008

Growing interest in converting the energy of California’s ocean waves into electricity is matched by concerns regarding the potential effects of wave energy conversion technology on marine resources. This study finds ecological and socio‐economic challenges associated with wave energy conversion are likely to depend fundamentally on project scale and location. Social and cultural impacts to fisheries, marine transportation, and some recreation are expected, and may have economic ramifications. Changes to the physical environment are predicted to result from a reduction in wave energy and alterations to nearshore wave‐driven processes. Benthic communities may exhibit direct or indirect responses to these changes, with the potential for non‐linear effects. Fish are expected to use wave energy conversion installations as artificial habitat, and environmental perturbations such as acoustic or electro‐magnetic stimuli may affect behavior. Marine bird and mammals effects are expected to be minimal, but there is cause for caution regarding select species. Dramatic ecological, social, or economic effects are not clearly indicated by this study, but a strong case for caution is supported when developing wave energy conversion technology off the California coast. Impacts to human activities, wave exposure, benthic communities, fishes, birds and mammals are all virtually certain, but the impacts’ magnitudes and the cumulative effects remain difficult to anticipate.

A Review of California Mussel (Mytilus californianus) Fisheries Biology and Fisheries Programs

Article

D. Schmidt

Optimization of an "in situ" subtidal rocky-shore sampling strategy for monitoring purposes

Article

Jul 2013

Nested PCR detection of microscopic life-stages of laminarian macroalgae and comparison with adult forms along intertidal height gradients

Article

Full-text available

Mar 2007

Recruitment of kelp species (Laminariales) to rocky marine habitats relies on the prior establishment of microscopic life-stages (zoospores, gametophytes, gametes and microscopic sporophytes). Unlike macroscopic sporophyte stages of kelp, microscopic life-stages have proved difficult to detect and identify in their natural habitat. Using a species-specific PCR-based assay, we developed a method to detect putative microscopic life-stages of 2 northeast Pacific kelp species, Nereocystis luetkeana (Mertens) Postels et Ruprecht and Hedophyllum sessile (C. Agardh) Setchell, from rocky intertidal substrate samples. Species-specific primers were evaluated for specificity and sensitivity. Comparisons of nested and unnested PCR were performed for both species. Nested PCR was used to screen for target species present on rocks obtained along an interticlal height gradient (0.0 to 3.5 m Lowest Low Water [LLW]) from 2 sites at monthly intervals in summer 2005. Vertical distribution patterns of the putative microscopic life-stages and the macroscopic sporophyte form were compared at both sites. Putative microscopic life-stages of N. luetkeana were detected at both sites and displayed a widespread vertical distribution with no clear spatial or temporal relationship. In comparison, H. sessile putative microscopic life-stage distribution was much more spatially restricted, showing a similar distribution to the macroscopic sporophyte. This study demonstrates the sensitivity, specificity and validity of utilizing molecular techniques to describe the distribution of microscopic life-stages of certain kelp species.

Population, morphometric and biomechanical studies of three understory kelps along a hydrodynamic gradient

Article

Full-text available

Dec 2003

Kelps (benthic algae in the order Laminariales) live in a highly dynamic fluid environment, and exhibit many adaptations to meet the challenges imposed by hydrodynamic forces. We examined flow effects (direct and indirect) on understory kelp population dynamics, morphology and biomechanics along gradients of current velocity and wave accelerations in the San Juan Archipelago, Washington. Costaria costata, Agarum fimbriatum, and Laminaria complanata all exhibited significantly higher mortalities at wave-impacted sites, but no gradient was detectable in the effects of tidal currents on survival, despite the strong tidal signal in waters of the archipelago. This pattern stands in contrast to that reported earlier for the surface-canopy bull kelp Nereocystis luetkeana in these waters; N. luetkeana mortality was strongly correlated with current, but not wave energy. The higher wave-driven mortalities of the understory species occur, even though a suite of morphological and biomechanical attributes (thallus size and thickness, holdfast area and biomass, stipe cross-sectional area, holdfast strength, blade toughness) indicate that kelps at sites characterized by high flow energy are better adapted to resist the forces imposed by waves and currents. While the forces imposed by strong currents have little effect on survival, they do have significant effects on morphology and biomechanical strength. We propose that morphological plasticity in A. fimbriatum and C. costata ameliorates the effects of both currents and waves on their survival.

The Role of Reproductive Synchrony in the Colonization Potential of Kelp

Article

Full-text available

Dec 1997

Dispersal is a key element in the recovery of populations that have been locally destroyed by disturbance. Surprisingly, many sessile species that seemingly have limited potential to disperse often rapidly colonize areas that have been recently disturbed. The synchronous release of propagules during periods that promote advection may extend the dispersal of such species and promote their rapid colonization. Alternatively, rapid recovery may result from colonization by dormant stages that survive disturbance. Here we test for reproductive synchrony as a way of extending the dispersal potential of two common seaweeds, the kelps Macrocystis pyrifera and Pterygophora californica. Synchrony in spore release in their case is likely to be particularly useful in extending colonization distance because fertilization in these species occurs after spore dispersal; synchrony increases the chance of fertilization by increasing the concentration of spores. We also evaluate experimentally the relative importance of dormant stages vs. recently settled spores in accounting for the rapid recovery of local kelp populations following severe disturbances. Reproductive synchrony was evaluated by following weekly changes in the reproductive condition of adult kelp. The degree of reproductive synchrony in both Macrocystis and Pterygophora was significantly greater than that expected under conditions of asynchronous reproduction. In Macrocystis, periods of synchronous spore production and release occurred sporadically over a 2-yr period. At least 75% of the sampled population exhibited the same directional change in reproductive condition in 38 of 82 sample periods. Episodes of significant spore release varied in duration from as little as 1 wk to as much as 2 mo. The sharpest decline in reproductive condition occurred during a severe storm. In contrast to Macrocystis, relatively well defined cycles of spore production, maturation, and release were observed in Pterygophora. More than one cycle was observed within a single reproductive season, and each cycle lasted ~3-4 wk. The different patterns and degrees of synchrony observed between the two species likely reflect the degree to which their production of spores is influenced by environmental conditions; spore production in Macrocystis is greatly influenced by fluctuations in seawater temperature and nutrients while spore production in Pterygophora is not. Results from field experiments comparing the recruitment of small plants among rocks placed in the kelp bed for varying lengths of time indicated that microscopic life stages of Macrocystis and Pterygophora have little capacity for dormancy, and that the vast majority of recruitment resulted from recently settled spores. These results contrasted with those observed for the annual brown alga Desmarestia ligulata which showed a dormancy period of several months. Our findings suggest that mechanisms such as reproductive synchrony that extend the distances over which kelp spores can effectively colonize are likely to play a critical role in the dynamics of kelp populations, which often fluctuate greatly in time due to disturbance.

Measuring ecosystem function: Consequences arising from variation in biomass-productivity relationships

Article

Full-text available

Jun 2008

Species diversity loss is expected to alter ecosystem function, but previous work has demonstrated inconsistent relationships between these two factors. Productivity is the most common measure of ecosystem function, but given the difficulty in measuring productivity, standing biomass or change in biomass are frequently used as proxy measures. A review of the recent ecosystem-function literature revealed that 93% of studies measure productivity as biomass, thereby assuming a strong positive relationship between these two variables. We tested this assumption by measuring biomass and productivity in seagrass beds in the Gulf of Mexico. We found that the relationship between standing biomass and productivity could be positive or negative, depending on site. Change in biomass over months inconsistently underestimated short-term productivity. The relationship between biomass and productivity may depend on plant age, successional stage, or site-specific rates of tissue loss to herbivory, senescence, or disturbance. Our results suggest that if biomass continues to be used as a measure of productivity without justification, highly productive communities that typically show little change in biomass, such as healthy climax communities, will not be interpreted as such. The conflicting results of previous studies investigating the relationship between diversity and productivity may be due to differences in the inherently variable relationship between biomass and productivity at different sites and scales.

Disturbance and subsequent recovery of mid-shore assemblages on seasonal, tropical, rocky shores

Article

Full-text available

Mar 2003

Hong Kong experiences a strongly seasonal climate, with distinct hot, wet summers and cool, dry winters, which has a great influence on intertidal assemblages. The impacts and relative importance of disturbance events on assemblage structure and subsequent recovery in this environment were examined on semi-exposed rocky shores. In August 1997, Typhoon Victor affected Hong Kong coastal waters bringing high seas and strong winds. Effects on mid-shore assemblage structure were patchy, with an increase in free space and a decrease in the abundance of the dominant molluscan grazer Monodonta labio occurring on one 10 m site on a shore, but not at other areas 10s of m away. The long-term impacts of this pulse disturbance were, however, negligible, as at this time of year there is little algal cover and grazer abundances are low, due to predictable annual disturbance caused by an increase in temperature with the onset of summer. Monitoring of plots artificially disturbed at different times of the year showed that recovery to undisturbed conditions was rapid following pulse disturbance events such as typhoons. Such disturbances had no lasting (> 6 mo) effect, as the die-off of species in the summer caused assemblages on shores to dissipate, and any long-term impacts of these disturbances were not obvious after one summer. It appears that the short-term effects of pulse disturbances on Hong Kong shores are rapidly eclipsed by annual, summer die-off events.

The significance of spatial and temporal patterns of algal mat deposition in structuring salt marsh vegetation

Article

Jun 2006
J VEG SCI

Question: Are there hot spots of algal mat deposition in space and time at the marsh scale and, if so, how does this affect the coexistence of a dominant (Spartina anglica) and gap dependent (Salicornia europaea) species? Location: The Rattekaai salt marsh in the Scheldt estuary in the southwestern Netherlands (NW Europe). Methods: Mat cover and the abundance of the gap dependent species Salicornia europaea were monitored at the scale of a marsh. The effects of mat cover on the vegetation structure were studied by applying three mat removal treatments over three growing seasons. Results: The low marsh border was found to be a hot spot of algal mat deposition during the growing season, which had a correlated spatial pattern between two successive years at a 20 m X 20 m scale. The combination of duration, timing and repetition of mat cover determined growth inhibition of the competitive dominant Spartina anglica, and thereby the abundance of subordinates such as Salicornia europaea. Mat cover reduced the storage of carbon reserves in Spartina and our results imply that repetition of non-lethal mat cover can lead to ‘gap creation’. Gaps gave only temporary habitat to less dominant species since Spartina quickly re-invaded them. The gap dependent annual Salicornia was most abundant at intermediate levels of disturbance measured as a function of both space and time. Conclusions In addition to disturbance level, the spatial and temporal distribution of disturbance are important in creating and maintaining habitat for gap dependent species. Relatively small disturbances will have a large effect on diversity if the spatial and temporal distribution of the disturbances leads to ‘disturbance hot spots’.

Role of nutrient fluctuations and delayed development in gametophyte reproduction by Macrocystis pyrifera (Phaeophyceae) in Southern California

Article

Sep 2010
J PHYCOL

Organisms occurring in environments subject to severe disturbance and/or periods of poor environmental quality that result in severe adult mortality can survive these periods by relying on alternate life stages that delay their development in a resistant state until conditions improve. In the northeast Pacific, the forest-forming giant kelp Macrocystis pyrifera (L.) C. Agardh periodically experiences widespread adult mortality during extended periods of extremely low nutrients and high temperatures, such as those associated with El Niño. Recovery following these periods is hypothesized to occur from microscopic life stages that delay their development until the return of favorable conditions. In the laboratory, we experimentally examined the environmental conditions responsible for regulating delayed development of the microscopic stages of M. pyrifera from Southern California, USA. Nutrients controlled the delay and resumption of gametophyte growth and reproduction, perhaps linked to the large fluctuations in nutrients occurring seasonally and interannually in this region. Although growth of gametophytes proceeded in the virtual absence of nitrate, both nitrate and other trace nutrients were necessary for gametogenesis. Upon exposure to elevated nutrients, delayed gametophytes produced sporophytes more quickly (5–20 d) and at smaller sizes (10–200 μm) than gametophytes that had never been delayed (18–80 d, 80–400 μm, respectively), reducing negative density-dependent effects. This finding demonstrates that delayed gametophytes of M. pyrifera rapidly utilize increased resources to consistently produce sporophytes. Further work is needed to assess their potential role in population recovery following periods of poor environmental quality.

Type and timing of disturbance modify trajectories of recovery of rockpool assemblages at Aguda (NW Portugal)

Article

Apr 2011
J EXP MAR BIOL ECOL

Ecology of Marine Mussels

Chapter

Nov 2021

Elizabeth Gosling

Global and local distribution patterns of representative marine mussel species are presented in this chapter. The major physical factors that influence marine mussel distribution and abundance are temperature, salinity and hydrographic factors, while local distribution is also influenced by temperature and salinity in addition to wave force and changes in immersion patterns, which are monitored by data loggers. Predators, pests, fouling organisms and competitors are biological factors that influence local distribution in intertidal and shallow water environments. Significant predators are whelks, crabs, sea stars, birds, sea urchins, lobsters and flatfish. The most common pests are boring sponges, polychaetes and peacrabs, while ~100 invertebrate species have been identified as fouling organisms on mussel ropes. Mussels are the most prominent competitors for space in mid‐ to low‐shore areas on gently sloping rocky shores. The final part of this chapter considers the potential and observed impacts of climate change on marine ecosystems.

Ecology of bivalves

Chapter

Jun 2015

Elizabeth Gosling

In this chapter the effects of temperature and salinity, the two most important physical factors governing the distribution of marine organisms, are described in detail. Their effects on other aspects of bivalve biology, such as feeding, reproduction, growth, and respiration and osmotic regulation, are covered. Geographical distribution is also governed by hydrographic barriers to larval dispersal, such as oceanic currents, confluences, gyres and surface water stratification. For burrowing bivalves, additional physical factors such as substrate type and oxygen concentration come into play, while predation and competition once again are important biological factors. The chapter deals with main predators (Gastropods, Starfish, Asterias rubens,Crabs etc.) of bivalves, along with major pests, fouling organisms and competitors. Possible predators of larvae include sea squirts, ctenophores, sea anemones, barnacles, and larvae of various crustacean, echinoderm and fish species. Finally, the potential and observed impacts of climate change on marine ecosystems are also discussed.

THE ROLE OF REPRODUCTIVE SYNCHRONY IN THE COLONIZATION POTENTIAL OF KELP

Article

Dec 1997

Reproductive synchrony was evaluated by following weekly changes in the reproductive condition of adult kelp. The degree of reproductive synchrony in both Macrocystis and Pterygophora was significantly greater than that expected under conditions of asynchronous reproduction. In Macrocystis, periods of synchronous spore production and release occurred sporadically over a 2-yr period. At least 75% of the sampled population exhibited the same directional change in reproductive condition in 38 of 82 sample periods. Episodes of significant spore release varied in duration from as little as 1 wk to as much as 2 mo. The sharpest decline in reproductive condition occurred during a severe storm. In contrast to Macrocystis, relatively well defined cycles of spore production, maturation, and release were observed in Pterygophora. More than one cycle was observed within a single reproductive season, and each cycle lasted ∼3–4 wk. The different patterns and degrees of synchrony observed between the two species likely reflect the degree to which their production of spores is influenced by environmental conditions; spore production in Macrocystis is greatly influenced by fluctuations in seawater temperature and nutrients while spore production in Pterygophora is not. Results from field experiments comparing the recruitment of small plants among rocks placed in the kelp bed for varying lengths of time indicated that microscopic life stages of Macrocystis and Pterygophora have little capacity for dormancy, and that the vast majority of recruitment resulted from recently settled spores. These results contrasted with those observed for the annual brown alga Desmarestia ligulata which showed a dormancy period of several months. Our findings suggest that mechanisms such as reproductive synchrony that extend the distances over which kelp spores can effectively colonize are likely to play a critical role in the dynamics of kelp populations, which often fluctuate greatly in time due to disturbance.

SIZE AND SURVIVAL OF INTERTIDAL PLANTS IN RESPONSE TO WAVE ACTION: A CASE STUDY WITH FUCUS GARDNERI

Article

Jul 1997

Carol Blanchette

Hydrodynamic forces generated by breaking waves have been proposed to act as one of the primary physical mechanisms constraining the sizes to which wave-swept intertidal plants can grow. Plants inhabiting intertidal areas are generally small relative to subtidal and terrestrial plants, and within a species, plants on wave-exposed shores are usually smaller than those at wave-protected sites. However, although these relationships have been well documented, there have been no manipulative field experiments demonstrating that wave forces are directly responsible for limiting plant sizes. In this study, I examined the effects of wave forces on plant sizes in the field by reciprocally transplanting Fucus gardneri (rockweed) individuals between wave-exposed and wave-protected intertidal sites at Fogarty Creek Point, Oregon. Mean sizes of wave-exposed plants transplanted to protected sites increased significantly relative to exposed control transplants. Mean sizes of wave-protected plants transplanted to exposed sites decreased significantly relative to protected control transplants. These data support but modify an accompanying mathematical model that predicts size-dependent survivorship of Fucus under conditions of high and low wave exposure. This model incorporates the trade-off between higher reproductive capacity and lower probability of survival at larger plant sizes. “Optimal” plant sizes predicted by the model closely match the mean observed sizes of plants collected from exposed and protected locations. However, the match between observed and predicted plant sizes occurred not via differential survivorship, but by direct size modification resulting from plant tattering. In this study, I examined the effects of wave forces on plant sizes in the field by reciprocally transplanting Fucus gardneri (rockweed) individuals between wave-exposed and wave-protected intertidal sites at Fogarty Creek Point, Oregon. Mean sizes of wave-exposed plants transplanted to protected sites increased significantly relative to exposed control transplants. Mean sizes of wave-protected plants transplanted to exposed sites decreased significantly relative to protected control transplants.

THE ROLE OF ALTERNATE LIFE-HISTORY STAGES OF A MARINE MACROALGA: A SEED BANK ANALOGUE?

Article

Sep 2000

Matthew Edwards

Short-range dispersal maintains a volatile marine metapopulation: The brown alga Postelsia palmaeformis

Article

Mar 2017

The annual brown alga Postelsia palmaeformis is dependent for its survival on short-distance dispersal (SDD) where it is already established, as well as occasional long-distance colonization of novel sites. To quantify SDD, we transplanted Postelsia to sites lacking established plants within ≥10 m. The spatial distribution of the first naturally produced sporophyte generation was used to fit dispersal kernels in a hierarchical Bayesian framework. Mean dispersal distance within a year ranged from 0.16 to 0.50 m across sites; 95% of the recruits were within 0.38 to 1.32 m of the transplant. The fat-tailed exponential square root kernel was the best among the candidate models at describing offspring density and dispersal. Independent measurements of patch size over 2-5 generations permitted an evaluation of whether models parameterized by individual-level data could adequately predict longer-term persistence and spread at the patch scale. The observed spread rates generally fell within the 95% predictive intervals. Finally, Postelsia was eliminated from 14 occupied sites that were then followed for ≥27 years. The probability of invasion when unoccupied declined and the probability of extinction when occupied increased with distance from the nearest propagule source. Sites >10 m from a source were rarely invaded, and one initially densely populated site isolated by 39 m has remained Postelsia-free since 1981. In spite of dispersal that is almost entirely within 2 m of the parent, the ability of our models to capture the observed dynamics of Postelsia indicates that short-range dispersal adequately explains the persistent and thriving Postelsia metapopulation on Tatoosh Island. However, the presence of Postelsia over a 2000-km coastal range with many gaps >1 km makes it clear that rare long-distance dispersal must be required to explain the geographic range of the species. This article is protected by copyright. All rights reserved.

Meiospores produced in sori of non-sporophyllous laminae of Macrocystis pyrifera (Laminariales, Phaeophyceae) may enhance reproductive output

Article

Full-text available

Apr 2014
J PHYCOL

Different lamina of Macrocystis pyrifera sporophytes, i.e., sporophylls, pneumatocyst-bearing blades, and apical scimitars, in a wave-sheltered site were found to be fertile. We quantified their sorus surface area, reproductive output (number of spores released) and the viability of released spores (germination rate). Sorus area was greatest on the sporophylls, with sporangia developing on > 57% of the total area and smallest on the pneumatocyst-bearing blades with 21% of the total area bearing sporangia. The apical scimitar released the greatest number of meiospores (cells · mL-1 · cm-2) and the sporophylls the least. Meiospores produced from all types of fertile laminae were equally viable. This reproductive plasticity may enhance reproductive output, and contribute to short and long-distance spore dispersal and the cryptic gametophyte propagule bank for the next generation of sporophytes. This article is protected by copyright. All rights reserved.

Temporal Changes in an Interaction Between an Indigenous LimpetScutellastra Argenvillei and an Alien Mussel Mytilus Galloprovincialis: Effects of Wave Exposure

Article

Full-text available

Jun 2003

A previous survey of 15 sites off the Namaqualand coast on the west coast of South Africa provided evidence of a competitive interaction between an alien mussel Mytilus galloprovincialis and an indigenous limpet Scutellastra argenvillei, and indicated that wave action mediates the strength of this interaction. In this study, the temporal persistence of these patterns was tested by selecting six sites, ranging from sheltered to very exposed, and monitoring them over a two-year period. The patterns remained consistent over time. Both S. argenvillei and M. galloprovincialis were perpetually absent from the most sheltered site. The limpet consistently dominated rock space at the semi-exposed site where mussel cover was always low. At exposed sites, M. galloprovincialis was dominant but its percentage cover varied temporally as a result of wave action, creating free space and allowing temporary expansion of limpet patches. However, with time the mussel recolonized the cleared rock space and repeatedly displaced the limpet from it. This provides additional observational evidence of competition for space between the alien invader and the indigenous limpet. It is concluded that S. argenvillei has a spatial refuge from M. galloprovincialis in areas with moderate wave action. However, the limpet is likely to become locally extinct on exposed shores because mussels outcompete it there and rapidly recolonize patches from which they have been temporarily eliminated by wave action.

Inconsistency and variation in the development of intertidal algal assemblages

Article

Jun 1998
J EXP MAR BIOL ECOL

Experimentally-cleared patches were used to test hypotheses about the relative importance of broad-scale biogeographic processes and small-scale historical processes in the development of low-shore algal assemblages on wave-exposed rocky coasts of New South Wales (Australia). In addition, the applicability of generalizing from patterns of recruitment and development at one time was tested by providing similar cleared patches in the algal assemblage at three-monthly intervals and quantifying early development of the algal assemblage in these clearings fifteen times over a period of four years.The early stages of development of these assemblages differed significantly from shore to shore and time to time and there was no evidence for common broad-scale patterns of recruitment, nor for any biogeographic trend. Nevertheless, these assemblages developed from a limited common pool of species, some of which recruited fairly regularly on most shores and some of which only arrived sporadically on some shores. Despite different starting points, assemblages converged towards the surrounding assemblages on most shores, so that within less than 1–2 years, cleared areas resembled the surrounding assemblages. Although the specific changes leading to convergence differed from shore to shore, there was a general pattern of early colonizers, such as ephemeral algae and sessile animals being gradually replaced by larger perennial algae.These results demonstrate no simple seasonal nor clear-cut biogeographical patterns in the development of algal assemblages on these shores and indicated the relative importance of local influences. Results are discussed with respect to the need to do experiments at numerous places in order to examine responses of assemblages to, or recovery from, environmental disturbances.

An experimental analysis of crayfish (Orconectes rusticus) effects on a Dreissena-dominated benthic macroinvertebrate community in western Lake Erie

Article

Apr 2011
CAN J FISH AQUAT SCI

Quantitative descriptions of trophic interactions between Dreissena (zebra and quagga mussels) and other organisms are needed for an understanding of Dreissena's effects on energy flow and community dynamics in the Great Lakes. We used a field experiment to quantify effects of crayfish (Orconectes rusticus) predation on a Dreissena-dominated benthic macroinvertebrate community in western Lake Erie. Rocks colonized by Dreissena and associated macroinvertebrates were placed in cages and cageless reference plots located at a depth of 4 m. Crayfish (0, 8.3, and 20.8 individuals ·m-2) placed in cages were allowed to graze for 28 days. Dreissena had a greater effect than crayfish on the macroinvertebrate community, with positive relationships observed between Dreissena densities and both total macroinvertebrate biomass and densities of the amphipod Gammarus fasciatus. However, crayfish at densities of 20.8 individuals ·m-2 still reduced non-Dreissena macroinvertebrate biomass and Gammarus densities by 33 and 37%, respectively, relative to crayfish exclosures. Crayfish had negligible effects on Dreissena densities or shell length frequency distribution. Because crayfish and amphipods are prey for several fish species, trophic interactions among Dreissena, amphipods, and crayfish may be important in channeling energy from Dreissena to higher trophic levels in the Great Lakes.

Water motion, marine macroalgal physiology, and production

Article

Dec 2001
J PHYCOL

Catriona Hurd

Water motion is a key determinant of marine macroalgal production, influencing directly or indirectly physiological rates and community structure. Our understanding of how marine macroalgae interact with their hydrodynamic environment has increased substantially over the past 20 years, due to the application of tools such as flow visualization to aquatic vegetation, and in situ measurements of seawater velocity and turbulence. This review considers how the hydrodynamic environment in which macroalgae grow influences their ability to acquire essential resources and how macroalgae might respond physiologically to fluctuations in their hydrodynamic regime with a focus on: (1) the biochemical processes occurring within the diffusion boundary layer (DBL) that might reduce rates of macroalgal production; (2) time scales over which measurements of velocity and DBL processes should be made, discussing the likelihood of in situ mass transfer limitation; (3) if and how macroalgal morphology influences resource acquisition in slow flows; and (4) ecobiomechanics and how hydrodynamic drag might influence resource acquisition and allocation. Finally, the concept that macroalgal production is enhanced in wave-exposed versus sheltered habitats is discussed.

Dispersion, Dispersal, and Persistence of the Annual Intertidal Alga, Postelsia Palmaeformis Ruprecht

Article

Full-text available

Mar 1973

Paul Dayton

Postelsia palmaeformis is an annual brown alga that occurs on the Washington coast at upper intertidal sites subjected to extreme wave exposure. The alga occurs in patches within beds of Mytilus californianus, the competitive dominant in this region. Postelsia sporophytes are shown to colonize experimentally cleared spaces in beds of Mytilus with no concurrent colonization of adjacent uncleared controls. However, unlike many annual algae which have high spore dispersal abilities, Postelsia seems to have an effective distance of sporophyte colonization of only about 3 m from the edge of existing Postelsia patch. This limited spore dispersal is the mechanism postulated to explain the observed within-patch aggregated distribution also. Postelsia patches are maintained through time by settlement of Postelsia on other algal and animal species. By increasing the probability of both being ripped from the substraturm, and by overgrowing and smothering barnacles, Postelsia sporophytes clear primary substratum for the eventual use of sporophytes of their own species.

Reproduction induced by blue light in female gametophytes of Laminari saccharina

Article

Full-text available

Sep 1972
PLANTA

In red light at 15°C, female gametophytes of Laminaria saccharina continue to grow indefinitely without becoming fertile, but 6-12 hours' irradiation with blue light induces the production of eggs. At lower temperatures, some gametophytes become fertile in red light, but blue irradiation increases the percentage of fertile gametophytes.

Dayton, P. K. Competition, disturbance, and community organization: the provision and subsequent utilization of space in a rocky intertidal community. Ecological Monographs

Article

Full-text available

Oct 1971

Paul k. Dayton

An understanding of community structure should be based on evidence that the growth and regulation of the component populations in the community are affected in a predictable manner by natural physical disturbances and by interactions with other species in the community. This study presents an experimental evaluation of the effects of such disturbances and competitive interactions on populations of sessile organisms in the rocky intertidal community, for which space can be demonstrated to be the most important limiting resource. This research was carried out at eight stations on the Washington coastline which have been ranked according to an exposure/desiccation gradient and subjected to comparable manipulation and observation. Physical variables such as wave exposure, battering by drift logs, and desiccation have important effects on the distribution and abundance of many of the sessile species in the community. In particular, wave exposure and desiccation have a major influence on the distribution patterns of all the algae and of the anemone Anthopleura elegantissima. The probability of damage from drift logs is very high in areas where logs have accumulated along the intertidal. Log damage and wave exposure have complementary effects in the provision of free space in a mussel bed, as wave shock enlarges a patch created by log damage by wrenching the mussels from the substratum at the periphery of the bare patch. Competition for primary space results in clear dominance hierarchies, in which barnacles are dominant over algae. Among the barnacles, Balanus cariosus is dominant over both B. glandula and Chthamalus dalli; B. glandula is dominant over C. dalli. The mussel Mytilus californianus requires secondary space (certain algae, barnacles, or byssal threads) for larval settlement, but is capable of growing over all other sessile species and potentially is the competitive dominant of space in the community.

Physical disturbances in an Australian kelp community. I. Temporal effects

Article

Full-text available

Oct 1987

Steven James Kennelly

Resource Partitioning and Competition within a Guild of Fugitive Prairie Plants

Article

Full-text available

May 1977

Badger disturbances on tall-grass prairies constitute a limiting resource for a guild of fugitive plants. These plants partition the resource along several dimensions. Divergent centers of resource utilization result from different suites of adaptive life-history characteristics important during colonization. While overlap of utilization functions is considerable along single dimensions of the resource, complementary adaptations of species result in reduced overlap along a complex gradient integrating the separate dimensions. We predict that the number, packing, and organization of species into a guild will change as the nature of the limiting resource changes. Specifically, changes in the abundance of the resource alter the heterogeneity of the resource over space, and as a result relationships among the adaptive centers of resource utilization for species also change. Predictions of changes in resource partitioning and guild organization, based upon assumptions concerning competition among species popul...

Gametogenesis, gametes and zygotes: An ecological perspective on sexual reproduction in the algae

Article

Full-text available

Sep 1992

Ecological aspects of sexual reproduction in freshwater and marine algae are reviewed in the context of reproductive seasonality, gamete release, pheromones, fertilization success, polyspermy, parthenogenesis, and the dispersal of zygotes. Fertilization success in freshwater and marine macroalgae is higher than previously assumed, and the biological and physical variables that contribute to this are reviewed and analysed. These variables include synchronous release of gametes, plant architecture, immobilization of female gametes, cytological specializations (e.g., in the spermatia of some red algae), agglutinins, and a number of important aspects of water motion. Little is known about fertilization success in unicellular algae, but various aspects (gametogenesis, resting zygotes) of reproduction in such algae are considered. The review concludes with questions that should be addressed in future studies; a number of these require more attention to hydrodynamic variables.

Physical disturbances in an Australian kelp community. II. Effects on understorey species due to differences in kelp cover

Article

Full-text available

Oct 1987

Steven James Kennelly

Physical disturbances in a sublittoral kelp community were investigated for their roles in structuring benthc assemblages. Effects of storms that lead to partial and/or complete denudation of kelp plants were investigated in a series of manipulative field experiments. Effects on understorey specles due to differential damage to kelp plants were examined by sampling replicate plots of treatments that imitated the various kinds of damage to kelps. Partial damage to kelp canopies led to similar effects on species to complete removal of kelps, because damaged plants invariably died. Encrusting algae and sponges decreased in cover in manipulated areas while microalgae and then brown turfing species increased in cover. Consequences of living on the borders of clearings in the kelp forest were investigated. Understorey assemblages here contained abundances of both those species found under the kelp canopy and those in the centres of clearings. Effects on understorey species due to thinning the kelp canopy to various densities was investigated. Thnning kelp canopies had similar effects for most species as complete removal of canopies. Fluctuations in abundances of certain species required the removal of at least 50 % of the kelp canopy. Effects on colonizing species of providing clean primary substrata under kelp canopies (as when kelp holdfasts are detached) were investigated. The identity of the various micro-algae that colonized areas of bare substrata under the canopy showed marked variabhty among replicate sites. Results illustrated several complex influences that physical disturbances have on the structure of a kelp community, and ~ndicate the need for comprehensive experimental studies of the effects of physical, disturbances.

Patch Dynamics and Stability of Some California Kelp Communities

Article

Full-text available

Sep 1984

This paper considers three concepts of stability as they relate to the dynamics of distinctive patch types of algal canopy guilds in southern and central California kelp communities: (1) persistence of a patch through more than one generation of the dominant species, which was evaluated by using life tables and observations of patch borders; (2) inertia or the resistance of different patches to invasion or disturbance, which was evaluated by artificially enhancing gametophytes by transplanting sporogenic material, by removing canopy, and by evaluating some important disturbance processes; and (3) resilience or recoverability of a patch following a perturbation sufficient to allow invasion of different species, which was studied by defining some of the mechanisms of successful invasion or succession. By working in distinct habitats in southern (Pt. Loma and Santa Catalina Island) and central (Pt. Piedras Blancas) California, we could evaluate different types of physical stresses as they related to these stability concepts. Taller perennial canopy guilds were dominant competitors for light, but were more susceptible to physical wave stress. Dominance hierarchies in the competition for light appeared to be reversed in areas exposed to increasing wave stress. The main causes of mortality at Pt. Loma were entanglement with storm-dislodged Macrocystis plants and, in some areas, sea urchin grazing. Mortality in central California was due to winter storms. In most cases, distinct patches resisted invasion for >10 yr. The mechanisms of resistance involved (1) competition for light and, possibly, nutrients, and (2) limits to spore dispersal. When succession occurred, it was often mediated by many factors, including seasonality of spore production, which coincided with winter storm-related mortalities; mechanisms of kelp dispersal, which were most effective via drifting plants and fragments of fertile material held against the substrate by invertebrates; and survivorship of gametophytes and small sporophytes, which was influenced by local scour and grazing. Appropriate spatial scales, stability, and succession studies in these kelp communities were determined by the size of the disturbed area, which varied from the free space resulting from detachment of single plants to the free space resulting from catastrophies such as overgrazing or unusual storms. Temporal scales were influenced by seasonality of disturbance and algal reproductive condition and aperiodic episodes of cool, nutrient-rich water advected into the patch. There appeared to be conflicting morphological adaptations of the canopy guilds: exploitation of light was enhanced at higher canopy levels, whereas the lower canopy levels were better adapted to tolerate stress from wave surge. The adaptations of the algae appeared to form four distinct groups of tactics: (1) ruderals or plants, such as Nereocystis and Desmarestia, with opportunistic life histories; (2) kelps, such as Macrocystis, adapted to exploitative competition for light and nutrients; (3) kelps (Eisenia, Dictyoneurum) adapted to physical stress such as wave surge; and (4) those algae, such as corallines and Agarum, adapted to heavy grazing. Within any given area, the relative patch stability was determined by biological relationships; between areas, the patch stability patterns were attributable to physical differences.

Light and temperature demands for growth and reproduction of laminarian gametophytes in southern and central California

Article

Full-text available

Dec 1978

The gametophytes of 9 laminarian species (4 from southern California, and 5 from central California, USA) became fertile in the unicellular stage (female gametophytes) or in a few-celled stage (male gametophytes), when appropriate temperatures and a sufficiently high quantum irradiance in the blue part of the spectrum were supplied. Vegetative growth, leading to the formation of filamentous gametophytes was light-saturated at relatively low irradiances (4 W m-2; equivalent to about 2 nE cm-2 sec-1 or an illuminance of 1000 lux), whereas 2 to 3 times this irradiance in continuous fluorescent cool white light was needed to induce the majority of the gametophytes to become fertile. An illuminance of 8300 lux did not inhibit the development of the gametophytes from southern Californian species. Egregia menziesii exhibited an exceptionally low quantum demand for induction of fertility. Gametophytes of species from central and southern California differed in regard to their temperature optimum for growth (12C in the former, 17C in the latter) and their upper temperature limit for reproduction (17C in the former, 20C in the latter).

On the discharge of eggs and spermatozoids of Laminaria japonica and the morphology of the spermatozoids

Article

Jan 1959

Patterns of reproduction, dispersal and recruitment in seaweeds

Article

Jan 1990

Bernabe Santelices

The role of light in the ecology of Laminaria hyperborea. In Light as an Ecological Factor

Article

INFLUENCE OF INTERSPECIFIC COMPETITION AND OTHER FACTORS ON DISTRIBUTION OF BARNACLE CHTHAMALUS STELLATUS

Article

Oct 1961

Joseph H. Connell

Some Causes of Variety in Patterns of Secondary Succession

Chapter

Jan 1981

Henry S. Horn

The contrasts and paradoxes of ideas about succession are well illustrated by the history of my own ideas about succession. My introduction was the Boy Scouts’ Wildlife Management Merit Badge pamphlet (Allen 1952); old fields are invaded by sun-loving species, which by their growth gradually create an environment in which only shade-tolerant species can thrive. My observation at Camp Quinapoxet in West Ridge, New Hampshire was that all the sun-loving gray birches (Betula populifolia) are on sandy uplands and all the shade-tolerant hemlocks (Tsuga canadensis) are in ravines, regardless of the ages of the stands.

The activity pattern and food habits of the limpet Acmaea pelta

Article

Jan 1968
VELIGER

P. Craig

A view of the genus Laminaria

Article

Jan 1979

J.M. Kain

The implications of transplant and culture experiments on the growth and distribution of Alaria esculenta

Article

Jan 1962

O. Sundene

Factors causing the lower limits of fucoid algae on the shore

Article

Jan 1980
J EXP MAR BIOL ECOL

Field and culture studies on fucoid alga of the upper shore showed that their lower limits of distribution were determined largely by interspecific competition. Pelvetia canaliculata (L.) Dcne. et Thur., which is strictly confined to the highest algal zone, grew much more slowly, both in culture and on the shore, than did Fucus spiralis L., which occupies the zone immediately below Pelvetia. When transplanted to the Fucus spiralis zone, macroscopic Pelvetia thalli grew normally, but Pelvetia zygotes which germinated within this zone reached macroscopic size only when competing Fucus spiralis was repeatedly removed. Both species required high light levels to grow in culture, yet their embryos remained viable for long periods in total darkness. Thus, Pelvetia cannot grow in the shade of Fucus spiralis, but actual removal of the Pelvetia germlings from the Fucus spiralis zone must be affected by some other factor. F. spiralis grew vigorously when transplanted to M.T.L., a level at which it is normally rare. In culture, its embryos grew more slowly than those of the species found lower on the shore such as F. vesiculosus L. and F. serratus L.; hence interspecific competition may again be involved. Young Ascophyltum nodosum (L.) Le Jol. plants grew almost as slowly as those of Pelvetia, yet Ascophyllum dominates the middle shore. In culture it showed only slightly greater tolerance of low light intensity than other fucoids but, unlike Pelvetia, persisted and grew beneath a Fucus canopy in the field. The possibility that differences in life history and palatibility to grazing molluscs contribute to the disparate competitive abilities of Pelvetia and Ascophyllum is discussed.

Population and Community Ecology of Seaweeds

Chapter

Dec 1987
ADV MAR BIOL

A. R. O. Chapman

Primary population parameters are examined in terms of mortality rates of both macroscopic algae and their modular components; determinants of mortality rates; reproduction; dispersal; and recruitment. Secondary population parameters are seen as genetic variation and age-class structure. Community ecology is reviewed in terms of vegetation structure, floristic classification, and determinants of structure, the last including biological interactions such as competition, herbivory and carnivory, and physico-chemical determinants of community structure. In some cases, seaweed distribution reflects physiological competence alone, but upper and lower limits are often set by herbivory and/or competition.-P.J.Jarvis

The Evolution of Complex Life Cycle Phenomena: An Ecological Perspective

Article

Sep 1967

Conrad A. Istock

A complex life cycle exists when the individuals of a species consistently pass through two or more ecologically distinct phases. Only the case with two phases (e.g., larval and adult) is considered in this paper. Manipulation of various life table and fertility measures make it possible to: (1) separate the larval and adult effects on the decline from maximum population growth to equilibrium; (2) derive a logistic equation for the growth of a population with a complex life cycle; and (3) define four possible states in which such a population might exist, one of which allows maximum realization of the ecological advantages of such a life cycle. To a great extent the evolutionary adaptations of the different phases of a complex life cycle are independent. Such independence is likely to make complex life cycles generally unstable over evolutionary time by moving the population away from maximum realization of the ecological advantages of such a life cycle. This will generate selective forces favoring a reduction or loss of one phase or the other. It is possible to interpret the degree to which the larval and adult phases are not equally responsible for population regulation as a measure of the degree to which selection is operating to maintain the complex life cycle character. There are characteristics of many present day species which seem to be the result of reduction or loss of one part of a complex life cycle.

Dispersal in Kelps: Factors Affecting Spore Swimming and Competency

Article

Oct 1992

The distance over which propagules can successfully colonize new sites depends on processes that increase the time they remain competent while being dispersed. As do feeding larvae, algal spores can contribute to their own nutrition (via photosynthesis) during dispersal. We explored the dispersal potential of the kelps Macrocystis pyrifera and Pterygophora californica in laboratory experiments by examining (1) how long their spores can swim, (2) the contribution of energy derived from photosynthesis to spore swimming duration, and (3) the ability of spores to germinate and attach after they stop swimming. Results indicate that under photosynthetically saturating irradiance no spores of either species can swim longer than 120 h; <10% of the spores were still swimming after 72 h. When placed in the dark, spores did not swim longer than 72 h; <10% remained swimming after 48 h. More importantly, spores did not die after they stopped swimming; most germinated in the water column and retained their capacity to produce viable sporophyte recruits. The ability of spores to attach after they stopped swimming differed between the two species; settlement density declined in Macrocystis and increased in Pterygophora. Thus, the viable planktonic stage of these algae is not necessarily restricted to the spore but may include later life history stages. These results provide biological evidence that the spores and germlings of these kelps can remain competent in the plankton for extended periods of time, which is consistent with our previous findings that their dispersal can occur over greater distances than previously thought possible.

The Effects of Variable Settlement and Early Competition on Patterns of Kelp Recruitment

Article

Apr 1990

Daniel C. Reed

Experimentally investigated the consequences of variable spore settlement and early (prerecruit) competition on the recruitment patterns of the sympatric sublittoral Macrocystis pyrifera and Pterygophora californica. For both kelps, a minimum density of at least 1 spore/mm2 was needed for successful recruitment. This minimum density was probably determined in part by the maximum distance that could separate male and female gametophytes while still allowing fertilization to occur. Although greater spore density often resulted in higher numbers of sporophyte recruits, strong density-dependent mortality still occurred whenever there was recruitment. "Safe sites' for the recruitment of kelp were highly variable in time; recruitment of both kelps was negatively correlated with the natural recruitment of ephemeral species of filamentous brown algae. Differences in post-settlement mortality between Macrocystis and Pterygophora often caused patterns of sporophyte recruitment to vary from those of initial spore settlement. Pterygophora spore settlement generally inhibited the recruitment of Macrocystis at both high (750-1500 spores/mm2) and low (10-20 spores/mm2) densities. Macrocystis settlement had no effect on Pterygophora recruitment. -from Author

Variation in Algal Dispersal and Recruitment: The Importance of Episodic Events

Article

Dec 1988

Macrocystis pyrifera and Pterygophora californica and filamentous brown algae (FBA) consisting primarily of Ectocarpus siliculosus were examined off S California. These three taxa of sublittoral brown algae show enormous differences in adult morphology and demography, but release propagules near the bottom that are similar in size, shape, and motility. Significant temporal variation was observed in recruitment at the zoospore source as well as at distances out to 4000 m from the source. For the kelp, this variation was due to variable rates of both zoospore settlement and early postsettlement mortality. In general, recruitment density of kelps rapidly declined with distance from the adult stand; significantly lower recruitment was observed at as little as 3 m away. For FBA, no significant decrease in recruitment density was observed out to 500 m. The differences in dispersal between these two algal groups may result from behavioral differences of their zoospores. Unlike those of kelps, zoospores of FBA are positively phototactic. This enables FBA zoospores to remain in the water column longer, thus increasing the distances over which they disperse. Turbulent water flow associated with winter storms may resuspend kelp zoospores normally occurring near the bottom and allow them to be transported greater distances by prevailing currents. Although species characteristics of the adults stand appeared to influence the distribution of recruits, the effect disappeared within 20 m of the stand. -from Authors

Habitat Suitability and Local Population Persistence of the Sea Palm Postelsia Palmaeformis

Article

Dec 1988

R. T. Paine

Sporophytes of the sea palm Postelsia normally occur on a variety of intertidal surfaces. An experimental technique was developed permitting spores to be sown onto natural substrata whose relative suitabilities were evaluated using three criteria. All major surface categories (bare rock, animal, plant) were equivalent if judged by the appearance the following spring of a descendant sporophyte. However, the proportion of these plants surviving to maturity and continuing into the following year was highly substratum dependent. Bare rock surfaces are the most suitable for Postelsia as judged by probability of successful occupancy, sporophyte density, and inter-annual persistence. Single fertile plants can establish or maintain a population. The probability of local extinction is a function of population size: only 36% of small populations (1-30 plants) tended to continue to the next year, whereas all those >120 individuals did. Postelsia seems incapable of persisting in the presence of the turf-like algae Corallina or Holosaccion. Thus sea palms may require the presence of competitively superior mussels: mussels out-compete algae of low stature; waves remove mussels, thereby generating Postelsia's most suitable substratum.

Experimental investigation into the controlling effects of light conditions on the development and growth of Desmarestia aculeata (L.) Lamour

Article

Mar 1970

Culture experiments designed to test the apparent correlation between the seasonal behaviour of Desmarestia aculeata and light conditions in the sea suggest that light intensity and daylength interact in their effect on development and growth, and that it is the total quantity of light energy received per day that is important in this resptect. Maturation of gametophytes took place between 54 lx and 1,540 lx mean daily illuminance (MDI) but was inhibited at lower levels. Mean daily . The rate of maturation of gametophytes increased with increasing MDI up to 615 lx. Similarly, the developmental rate of young sporophytes increased with increasing MDI, but there was no light saturation effect up to the maximum of 1,540 lx tested. The ability of gametophytes to produce young sporophytes was not impaired by a period of 93 days at a very low light intensity, since sporophytes developed at once with increased illumination. Marked elongation of regenerating branches on mature sporophytes took place at th...

Sexual reproduction and life history of Perithalia caudata (Sporochnales, Phaeophyta)

Article

Dec 1985

The life history of Perithalia caudata (Sporochnales) is reported. Meiospores of field specimens develop into dioecious microscopic gametophytes. Female gametophytes form oogonia and eggs, male gametophytes antheridia containing a single spermatozoid. Zygotes re-establish the diploid sporophyte phase. A low-molecular pheromone factor secreted by eggs stimulates spermatozoid-release and -attraction. Further morphological and physiological details on sexual reproduction reveal striking similarities between the orders Sporochnales, Desmarestiales and Laminariales and suggest a re-evaluation of their taxonomic relationships.

Survival of Juvenile Giant Kelp: The Effects of Demographic Factors, Competitors, and Grazers

Article

Apr 1989

Survival of juvenile Macrocystis pyrifera was poorer in areas where white sea urchins Lytechinus anamesus were abundant or where there was an overlying canopy of adults. At other sites, density of recruits explained the greatest proportion of variability in survival, and the proportion of juveniles that survived was negatively correlated with the number of recruits. Potential algal competitors (Pterygophora california, Cystoseira osmundacea), red sea urchins Strongylocentrotus franciscanus, and substrate distributions had no significant effect on survival. The mechanisms of density-dependent survival on the Californian coast were similar to "dominance and suppression' models that explain self-thinning in many terrestrial plant populations. In stands were densities of recruits were high, skewed size distributions developed, probably as the result of competition for light. High-density stands had proportionally more small plants than low-density stands and during subsequent storms, only larger plants survived. This led to a more equitable distribution of survivors than would be expected based on the number of recruits. -from Authors

The Effects of Canopy Shadings on Algal Recruitment and Growth in a Giant Kelp Forest

Article

Jun 1984

The subtidal (10—15 m) assemblage in the relatively sheltered giant kelp forest at Stillwater Cove in Carmel Bay, California, consists of perennial species forming three major vertical layers: a Macrocystis pyrifera surface canopy, a dense subsurface canopy of another kelp, Pterygophora californica, and an understory of articulated and encrusting coralline algae. The kelp canopies alone or in combination can reduce bottom light to <30% (usually <1%) of surface influx. The effects of light reduction by these vegetation layers on algal recruitment and subsequent growth were determined by removing various combinations of canopies over a 2—yr period, and following subsequent changes relative to appropriate controls. Removing both M. pyrifera and P. californica canopies resulted in moderate recruitment of these species as well as of the annual brown alga Desmarestia ligulata var. ligulata. None of these algae recruited into control areas where one or both canopies were left intact. Highest brown and red algal recruitment occurred when both kelp canopies plus understory coralline branches were removed. Removal of the latter alone had no significant effect. The time of year when algal canopies were removed had little effect on the composition of subsequent algal colonization, as the recruitment of noncalcareous species occurred primarily during a short period in the spring. These results indicate that the relatively low levels of both physical and biological disturbance in Stillwater Cove allow the establishment of a few perennial algal species that inhibit their own recruitment, as well as invasion of other species, by shading. This contrasts with nearby kelp forests subjected to greater and more frequent disturbance, and characterized by a diverse assemblage of annual algal species.

Ecological studies of economic red algae. III. Growth and reproduction of natural and harvested populations of Gigartina stellata (Stackhouse) Batters in New Hampshire

Article

Dec 1972
J EXP MAR BIOL ECOL

The growth in situ of populations of Gigartina stellata (Stackhouse) Batters has been recorded at three New Hampshire locations and correlated with seasonal and spatial variations of surface salinity, temperature, and nutrients. Annual growth began between February and May, depending upon the location and its hydrographic regime. Gigartina populations reached maximum biomass and size in August and September, and a general decrease in both occurred during the reproductive period from October to February. The period of fastest growth coincided with increasing summer temperatures, while maximum carpospore release occurred during the period of decreasing (coldest) temperatures. The largest plants and maximum biomass of Gigartina were found on the open coast (at a semi-exposed site) while smaller plants and reduced biomass were evident within the Great Bay Estuary System. Salinity is a dominant factor influencing both the local distribution and growth of the plant. Gigartina is primarily restricted to the littoral zone, and its maximum length and biomass occur between +0.45 and +1.0 m above M.L.W.Experimental plots were established to determine the effects of differential levels and seasons of harvesting on G. stellata. Summer (August) harvesting allowed control levels of biomass and population structure to be reached after one year, while winter (December) harvests attained control levels after 19 months. Denuded and sterilized quadrats required more than three years to re-establish themselves. Harvesting in December gave control levels of reproduction in the careful and moderately harvested plots after 9 and 12 months respectively. An August harvest deprived all the plots of reproductive potential until the following reproductive season.

A Study of Halicystis ovalis. I. Morphology and Reproduction

Article

Jan 1935

George J. Hollenberg

The settlement, attachment and establishment of marine alga spores

Article

Sep 1992

One of the most fundamental and precarious stages in the life history of a marine benthic alga is the colonization of a new substratum. For the majority of algae this is achieved by the formation and detachment of different types of highly specialized reproductive propagules which are then dispersed via the pelagic zone. This paper reviews the process of “settlement”, “attachment” and “establishment” of these propagules. Particular attention is given to the influence of substratum surface properties, both physical and chemical, on these processes, along with aspects of the derivation, chemical composition, mechanisms of release and mode of action of the various adhesives secreted by the attaching spores and germlings.

Intertidal Landscapes: Disturbance and the Dynamics of Pattern

Article

Jun 1981

The mussel Mytilus californianus is a competitive dominant on wave-swept rocky intertidal shores. Mussel beds may exist as extensive monocultures; more often they are an everchanging mosaic of many species which inhabit wave-generated patches or gaps. This paper describes observations and experiments designed to measure the critical parameters of a model of patch birth and death, and to use the model to predict the spatial structure of mussel beds. Most measurements were made at Tatoosh Island, Washington, USA, from 1970-1979. Patch size ranged at birth from a single mussel to 38 m^2; the distribution of patch sizes approximates the lognormal. Birth rates varied seasonally and regionally. At Tatoosh the rate of patch formation varied during six winters from 0.4-5.4% of the mussels removed per month. The disturbance regime during the summer and at two mainland sites was 5-10 times less. Annual disturbance patterns tended to be synchronous within 11 sites on one face of Tatoosh over a 10-yr interval, and over larger distances (16 km) along the coastline. The pattern was asynchronous, however, among four Tatoosh localities. Patch birth rate, and mean and maximum size at birth can be used as adequate indices of disturbance. Patch disappearance (death) occurs by three mechanisms. Very small patches disappear almost immediately due to a leaning response of the border mussels (0.2 cm/d). Intermediate-sized patches (

Evolution and Life Histories of Brown Algae

Article

Sep 1988

Margaret Clayton

Itertidal community structure. Experimental studies on the relationship between a dominant competitor and its principal predator

Article

Jan 1974
OECOLOGIA

RT Paine

Experiments on some effects of certain environmental factors on Gracilaria verrucosa (Hudson) Papenfuss

Article

Feb 1959
J MAR BIOL ASSOC UK

W. Eifion Jones

At an early stage of an autecological study of Gracilaria verrucosa (Hudson) Papenfuss it seemed possible that the best growth of the plants occurred in places, such as the Achill Sound and the Church Island Channel in the Menai Straits, where, in the absence of heavy wave action, strong currents flowed over the plants. Experiments were carried out, in the sea, to investigate the effect of currents on the growth rate; the apparatus used and described here would probably be suitable for the investigation of current effects on other sedentary marine organisms. These experiments also led to some observations on the effects of illumination on the pigmentation and growth rate of the plants which were supplemented by laboratory experiments. High intensity illumination in the laboratory also demonstrated positive phototropism in the plant.

Digestion survival of algae: some ecological comparisons between free spores and propagules in fecal pellets

Article

Oct 1990
J PHYCOL

Benthic algae survive passage through the digestive tract of different types of grazers, either regenerating new tissues or releasing protoplasts and swarmers which act as accessory means of reproduction to generate new individuals. The ecological importance of this phenomenon is evaluated here by studying spores and fecal pellets. Alga fragments egested alive inside fecal pellets have some ecological advantages over free propagules. In intertidal habitats, the sticky nature of the pellets permits attachment to the substratum while protecting the contained algae from desiccation. In subtidal habitats, the pellets sink 8–22 times faster than the fastest sinking algal propagule. Quantification of swarmers and protoplasts released from algal fragments in the fecal pellets indicates densities of about 217 germlings·cm−2 and values of 300–700 propagules per pellet. Extrapolation of these results to field conditions based on number of grazers and pellets suggest production figures varying from 0.5–3.5 × 105to 1.3–1.5 × 106 propagules·m−2·12 h−1. These values are within known density ranges of settling spores in the field. The ecological significance of the phenomenon may be especially important at seasons when the density of grazers increases and the normal reproductive activity of the algae being consumed decreases.

Critical irradiance levels and the interactive effects of quantum irradiance and dose on gametogenesis in the giant kelp, Macrocystis pyrifera

Article

Nov 2004
J PHYCOL

Gametophytes of Macrocystis pyrifera (L.) C. Ag. were cultured under a series of quantum irradiances in three photoperiod regimes. The quantum irradiances in each photoperiod were adjusted to provide equal daily irradiation dosages between photoperiods which allowed a critical examination of the interactions between quantum irradiance and quantum dose in determining gametophyte fertility. The lowest quantum irradiance which stimulated gametogenesis in more than 50% of the female gametophytes was 5 μE·m−2·s−1. The saturating irradiance was ca. 10 μE·m−2·s−1 at photoperiods of 12 h or greater. In terms of daily quantum dose, the lowest dose at which greater than 50% gametogenesis occurred was 0.2 E·m−2·d−1. However, this critical quantum dose was higher (0.4 E·m−2·d−1) when instantaneous irradiances were less than 5 μE·m−2·s−1. The saturation quantum dose was also affected by the rate at which the quantum dose was received and varied from 0.4 to 0.8 E·m−2·d−1. Gametophytes in all three photoperiods reached 100% fertility at quantum irradiances above 5 μE·m−2·s−1. Photoperiod effects were small and could be accounted for by quantum dosage effects.

Reproduction, recruitment and mortality in two species of Laminaria in southwest Nova Scotia

Article

Jun 1984
J EXP MAR BIOL ECOL

A. R. O. Chapman

In a southwestern Nova Scotia kelp forest the average density of Laminaria longicruris Pyle. remained constant through 1 yr at ≈1.2 plant·m−2. The density of L. digitata (Huds.) Lamour. was more variable through time, but averaged 3.2 plants·m−2. At these densities those plants which reproduced developed 8.9 × 109 and 20.02 × 109 spores·m−2·yr−1, respectively for L. longicruris and L. digitata. From the spores produced, 8.89 × 106 (L. longicruris) and 0.98 × 106 (L. digitata) microscopic benthic stages were recruited per m2 per yr. From this bank of microscopic stages, one sporophyte of L. longicruris and two of L. digitata grew to visible size per m2 per yr. Recruitment of visible sporophytes was enhanced ten-fold by removal of a red algal turf. Removal of macroscopic kelp plants had no effect on recruitment of visible stages. The rate of mortality among macroscopic individuals of L. longicruris (but not of L. digitata) was related to initial plant size and distance to nearest congeneric neighbour. Mortality rates of both species were unrelated to type and size of substratum or season of the year.

Intertidal amphipods as potential dispersal agents of carpospores of Iridaea lamniarioides (Gigartinales, Rhodophyta)

Article

Sep 1990
J PHYCOL

Mid and late successional benthic algae have poor dispersal capacities. Mobile herbivores may increase dispersal of some algae because spores can survive digestion by grazers and stick to external body appendages. We show that carpospores are the only type of reproductive unit of the rhodophyte Iridaea laminarioides Bory that survive passage through the digestive tract of the amphipod Hyale sp. The spores also stick to the amphipods' legs and are thus carried by the amphipods in the field. Amphipods significantly increased (P < 0.01) the number of spores settling on artificial substrata in places where barriers prevented the normal ingress of algal propagules. The presence of artificial substrata that act as a refuge for the grazers also caused an increase (P < 0.01) in the number of settled spores. Amphipods also significantly increased (P < 0.01) the number of spores under an Ulva sp. canopy in laboratory experiments.

Intertidal community structure

Article

Jan 1974

R. T. Paine

Along exposed rocky intertidal shorelines of western North America the mussel Mytilus californianus exists as a characteristic, well-defined band. Measurements at Mukkaw Bay and Tatoosh Island, Washington State, suggest that the upper limit to distribution is constant. The lower limit is also predictably constant, as judged by photographs of the same areas taken up to 9 years apart. The band of mussels is formed by larval recruitment to a variety of substrates, especially the filamentous red alga Endocladia muricata. From the settlement site, if the mussels survive a series of predators including the starfish Pisaster ochraceus and a variety of carnivorous gastropods (Thais spp.), the mussles may be washed inward or migrate (be pushed) downward. When Pisaster was removed manually, the zonation pattern changed rapidly. Mussels advanced downward at Mukkaw Bay a vertical distance of 0.85 m in 5 years. No movement was observed on 2 adjacent control sites. At Tatoosh Island a maximum displacement of 1.93 m has been observed in 3 years; the slope there is 40°. Again, there was no change at control sites with Pisaster. At Mukkaw Bay over 25 species of invertebrates and benthic algae are excluded from occupancy of the primary substratum by mussels. The ecological dominance of mussels is discussed; predation is shown to enhance coexistence among potential competitors. A survival curve for Pollicipes polymerus indicates that the time course for interspecific competitive exclusion may be long (76 months). The clarity of the biological interrelationships and the constancy of pattern through time provide no support for the contention that intertidal communities are physically-controlled.

Interactive efects of light and temperature on sporophyte production in the giant kelp Macrocystis pyrifera

Article

Oct 1986

Laboratory experiments were conducted in 1984 to test for an interaction between irradiance and temperature in controlling sporophyte production in the giant kelp Macrocystis pyrifera. Gametophytes from plants in the San Onofre kelp forest were cultured under a combination of seven irradiance (2.9 to 30 E m-2 s-1) and ten temperature (11 to 20C) levels. The minimum daily quantum dose for fertility of female gametophytes during the 42 d culture-period was 0.25 E m-2 d-1. The saturation quantum dose was approximately 0.60 E m-2 d-1. Temperatures between 11 and 20C had little effect on the fertilityirradiance relationship, except at irradiations near the threshold and saturation levels. Cultures at 0.60 E m-2 d-1 had significantly lower fertility after 6 wk at 20C than at the lower temperatures and there was a trend toward lower fertility at temperatures greater than 15C in cultures at 0.25 E m-2 d-1. These differences were also reflected in the development time for female gametophytes. The 11C cultures reached 50% fertility slightly faster and the 20C cultures slower than cultures at intermediate temperatures.

Response of Ecklonia radiata (Laminariales) to light at 15°C with reference to the field light budget at Goat Island Bay, New Zealand

Article

Jan 1984

Irene Novaczek

Gametophytes of Ecklonia radiata (C.Ag.)J.Ag. grew in culture at 15C under daily quantum doses ranging from 0.86 to 360 cE m-2. Growth rates increased with quantum doses up to 40 cE m-2 d-1, then reproduction began and the relative growth constant declined while ovum release came earlier with increasing light up to about 100 cE m-2 d-1. Above 100 cE m-2 d-1 there were no consistent trends with increasing light, except that at the higher quantum doses, fertile female plants had fewer and larger cells and therefore fewer potential ova. Reproduction varied with daily quantum dose rather than with daylength. Given the same daily dose, plants grew fastest in low photon flux density, long daylength conditions. Gametophytes grown in the field developed at similar rates to those in culture. Gametophytes survived seven months of darkness at 10C but died after one week of darkness at 20 to 23C. Sunlight of 1 000 E m-2 s-1 was fatal to gametophytes and to sporophytes under 2 mm long after 10 to 15 min. Light budgets were prepared for plants growing at 7-and 15-m depths from 1976 to May 1980 in Goat Island Bay, New Zealand (Lat.36 16S, Long. 174 48E). Underwater light was measured under various environmental conditions. Relationships between transmission of light through the sea, data from diving visibility records and continuous surface meteorological records were studied. Approximations were made of the average percentage of surface light transmitted to 7 and 15 m over half-monthly periods. By applying these average transmittance values to the records of surface incident light, the average daily quantum doses were calculated. Light on open bottom in Goat Island Bay may sometimes be limiting for gametophyte reproduction in winter at 15-m depth. At depths less than 7 m, summer photon flux densities may reach damaging levels.

Sublittoral ecology of marine algae on the North Wales coast

Article

Jul 1967

Roger M. Smith

1. Diving work carried out between April 1964 and July 1966 on the North Wales coast (Anglesey) showed that the west coast stations A and B could be divided into four distinct sublittoral regions, the east coast station showed a more irregular distribution of the flora. 2. The four distinct regions were: TheLaminaria forest, the rock below theLaminaria zone, the bed of loose stones supporting algae in summer, and the bed of sand supportingLaminaria saccharina. 3. The distribution of algae at station C was more dependant upon the local topography of the boulders making up the sea bed. 4. There was a difference between the fruiting periods of algae growing at a great depth and in the shallow water.

Effects of filter-feeders and grazers on algal settlement and growth in mussel beds

Article

Jun 1988
J EXP MAR BIOL ECOL

Macroalgae and mussels are common users of the often limiting primary space on mid- and low-intertidal rocky surfaces. As a result most studies of their interactions have focussed primarily on resource competition. Yet, frequently a diversity of algae is found coexisting with mussels — neither asphyxiating them nor being outcompeted by them. In this study, we look for other sets of ecologically important interactions between mussels and algae in the habitats where they coexist. Experimental studies showed that mussels ingest and digest algal spores, affect the pattern of algal settlement and protect the algal germlings from desiccation. Probably, they also fertilize the growing thalli. Small grazers among the mussels select the type of algae surviving in the bed and together with the abiotic environment control algal growth and abundance. Reproductive output, antiherbivore escape and defense mechanisms and tolerance to desiccation appear to be the most important algal adaptations for survival in this type of habitat. The resulting flora found among mussels is a function of all these interactions and of the age and history of the individual mussel bed.

Sousa, W. P. Disturbance in marine intertidal boulder fields: the nonequilibrium maintenance of species diversity. Ecology

Article

Dec 1979

Wayne Sousa

Sousa WP. The role of disturbance in natural communities. Annu Rev Ecol Syst

Article

Nov 1984
Annu Rev Ecol Systemat

Wayne Sousa

Food Web Complexity and Species Diversity

Article

Jan 1966

Robert T. Paine

It is suggested that local animal species diversity is related to the number of predators in the system and their efficiency in preventing single species from monopolizing some important, limiting, requisite. In the marine rocky intertidal this requisite usually is space. Where predators capable of preventing monopolies are missing, or are experimentally removed, the systems become less diverse. On a local scale, no relationship between latitude (10⚬ to 49⚬ N.) and diversity was found. On a geographic scale, an increased stability of annual production may lead to an increased capacity for systems to support higher-level carnivores. Hence tropical, or other, ecosystems are more diverse, and are characterized by disproportionately more carnivores.

Catastrophic Disturbance and the Steady State in Northern Hardwood Forests

Article

Jan 1979

A new look at the role of disturbance in the development of forest ecosystems suggests important implications for land-use policies.

Population Biolgy of Plants

Article

Jan 1977

John L. Harper

On the reproduction of some Pacific Coast species of Ulva

Article

Feb 1947

G M SMITH

Seasonal patterns of disturbance influence recruitment of the sea palm, Postelsia palmaeformis

Abstract

No full-text available

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