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The Effects of Ocean Acidification on Feeding and Contest Behaviour by the Beadlet Anemone Actinia equina
Abstract
Increasing concentrations of atmospheric carbon dioxide are causing oceanic pH to decline worldwide, a phenomenon termed ocean acidification. Mounting experimental evidence indicates that near-future levels of CO2 will affect calcareous invertebrates such as corals, molluscs and gastropods, by reducing their scope for calcification. Despite extensive research into ocean acidification in recent years, the effects on non-calcifying anthozoans, such as sea anemones, remain little explored. In Western Europe, intertidal anemones such as Actinia equina are abundant, lower trophic-level organisms that function as important ecosystem engineers. Changes to behaviours of these simple predators could have implications for intertidal assemblages. This investigation identified the effects of reduced seawater pH on feeding and contest behaviour by A. equina. Video footage was recorded for A. equina feeding at current-day seawater (pH 8.1), and the least (pH 7.9) and most (pH 7.6) severe end-of-century predictions. Footage was also taken of contests over ownership of space between anemones exposed to reduced pH and those that were not. No statistically significant differences were identified in feeding duration or various aspects of contest behaviour including initiating, winning, inflating acrorhagi, inflicting acrorhagial peels and contest duration. Multivariate analyses showed no effect of pH on a combination of these variables. This provides contrast with other studies where anemones with symbiotic algae thrive in areas of natural increased acidity. Thus, novel experiments using intraspecific contests and resource-holding potential may prove an effective approach to understand sub-lethal consequences of ocean acidification for A. equina, other sea anemones and more broadly for marine ecosystems.
... The foraging time was significantly longer due to the effects of OA in the sea urchin Strongylocentrotus fragilis (Barry et al., 2014). Some species such as the beadlet anemone Actinia equine have specific adaptability to OA; its feeding time and competition behavior under OA did not change significantly (Bamber et al., 2018). In a scavenging gastropod N. festivus, after short-term acidification treatment and returning back into the normal conditions, the foraging performance was able to return to a normal level (Leung et al., 2015). ...
Behavioral modification is the distinct response exhibited by marine animals to stressors. Exposure to oceanic environmental changes can alter the behaviors of aquatic animals, such as foraging, antipredation, habitat selection, and social hierarchy. Ocean acidification (OA) can alter the animal behaviors of a single species and thereby affect the structure and function of marine populations, communities, and ecosystems. Recently, the effects of OA on the behavioral responses of marine animals have received much attention. Considering the essential ecological functions and fishery value of marine living resources, we need to remain vigilant about the subsequent risk of OA. Here, we provide a systematic review including some classical case studies to highlight the effects of CO2-driven OA on the most common behaviors studied in marine animals and synthesize the current understanding of how OA may impact marine animal behaviors.
The effect of ocean warming and acidification on predator-prey interactions in the intertidal zone is a topic of growing concern for the scientific community. In this review, we aim to describe how scientists have explored the topic via research weaving, a combination of a systematic review, and a bibliometric approach. We assess articles published in the last decade exploring the impact of both stressors on predation in the intertidal zone, via experimental or observational techniques. Several methods were used to delve into how climate change-induced stress affected intertidal predation, as the study design leaned toward single-based driver trials to the detriment of a multi-driver approach. Mollusks, echinoderms, and crustaceans have been extensively used as model organisms , with little published data on other invertebrates, vertebrates, and algae taxa. Moreover, there is a strong web of co-authoring across institutions and countries from the Northern Hemisphere, that can skew our understanding towards temperate environments. Therefore, institutions and countries should increase participation in the southern hemisphere networking, assessing the problems under a global outlook. Our review also addresses the various impacts of ocean acidification, warming, or their interaction with predation-related variables, affecting organisms from the genetic to a broader ecological scope, such as animal behaviour or interspecific interactions. Finally, we argue that the numerous synonyms used in keywording articles in the field, possibly hurting future reviews in the area, as we provide different keyword standardizations. Our findings can help guide upcoming approaches to the topic by assessing what has been already done and revealing gaps in emerging themes, like a strong skew towards single-driver (specially acidification) lab experiments of northern hemisphere organisms and a lack of field multi-stressor experiments.
Carbon dioxide-induced ocean acidification is predicted to have major implications for marine life, but the research focus to date has been on direct effects. We demonstrate that acidified seawater can have indirect biological effects by disrupting the capability of organisms to express induced defences, hence, increasing their vulnerability to predation. The intertidal gastro-pod Littorina littorea produced thicker shells in the presence of predation (crab) cues but this response was disrupted at low seawater pH. This response was accompanied by a marked depression in metabolic rate (hypometabolism) under the joint stress of high predation risk and reduced pH. However, snails in this treatment apparently compensated for a lack of morphological defence, by increasing their avoidance behaviour, which, in turn, could affect their interactions with other organisms. Together, these findings suggest that biological effects from ocean acidification may be complex and extend beyond simple direct effects.
Interstate wars and animal contests both involve disputed resources, restraint and giving up decisions. In both cases it seems illogical for the weaker side to persist in the conflict if it will eventually lose. In the case of animal contests analyses of the links between opponent power and contest duration have provided insights into what sources of information are available to fighting animals. I outline the theory of information use during animal contests and describe a statistical framework that has been used to distinguish between two strategies that individuals use to decide whether to persist or quit. I then apply this framework to the analysis of interstate wars. War duration increases with the power of winners and losers. These patterns provide no support for the idea that wars are settled on the basis of mutual assessment of capabilities but indicate that settlement is based on attrition. In contrast to most animal contests, war duration is as closely linked to the power of the winning side as to that of the losing side. Overall, this analysis highlights a number of similarities between animal contests and interstate war, indicating that both could be investigated using similar conceptual frameworks.
Predicting the impact of warming and acidifying on oceans on the early development life history stages of invertebrates although difficult, is essential in order to anticipate the severity and consequences of future climate change. This review summarises the current literature and meta-analyses on the early life-history stages of invertebrates including fertilisation, larval development and the implications for dispersal and settlement of populations. Although fertilisation appears robust to near future predictions of ocean acidification, larval development is much more vulnerable and across invertebrate groups, evidence indicates that the impacts may be severe. This is especially for those many marine organisms which start to calcify in their larval and/or juvenile stages. Species-specificity and variability in responses and current gaps in the literature are highlighted, including the need for studies to investigate the total effects of climate change including the synergistic impact of temperature, and the need for long-term multigenerational experiments to determine whether vulnerable invertebrate species have the capacity to adapt to elevations in atmospheric CO2 over the next century.
Vermetids form reefs in sub-tropical and warm-temperate waters that protect coasts from erosion, regulate sediment transport and accumulation, serve as carbon sinks and provide habitat for other species. The gastropods that form these reefs brood encapsulated larvae; they are threatened by rapid environmental changes since their ability to disperse is very limited. We used transplant experiments along a natural CO2 gradient to assess ocean acidification effects on the reef-building gastropod Dendropoma petraeum. We found that although D. petraeum were able to reproduce and brood at elevated levels of CO2, recruitment success was adversely affected. Long-term exposure to acidified conditions predicted for the year 2100 and beyond caused shell dissolution and a significant increase in shell Mg content. Unless CO2 emissions are reduced and conservation measures taken, our results suggest these reefs are in danger of extinction within this century, with significant ecological and socioeconomic ramifications for coastal systems.
Background : Increased acidification/PCO2 of sea water is a threat to the environment and affects the homeostasis of marine animals. In this study, the effect of sea water pH changes on the osmotic phase (OP), regulatory volume decrease (RVD) and discharge of the jellyfish Pelagia noctiluca (Cnidaria, Scyphozoa) nematocytes, collected from the Strait of Messina (Italy), was assessed. Methods : Isolated nematocytes, suspended in artificial sea water (ASW) with pH 7.65, 6.5 and 4.5, were exposed to hyposmotic ASW of the same pH values and their osmotic response and RVD measured optically in a special flow through chamber. Nematocyte discharge was analyzed in situ in ASW at all three pH values. Results : At normal pH (7.65), nematocytes subjected to hyposmotic shock first expanded osmotically and then regulated their cell volume within 15 min. Exposure to hyposmotic ASW pH 6.5 and 4.5 compromised the OP and reduced or totally abrogated the ensuing RVD, respectively. Acidic pH also significantly reduced the nematocyte discharge response. Conclusion : Data indicate that the homeostasis and function of Cnidarians may be altered by environmental changes such as sea water acidification, thereby validating their use as novel bioindicators for the quality of the marine environment. © 2014 S. Karger AG, Basel.
Ocean acidification poses a range of threats to marine invertebrates; however, the potential effects of rising carbon dioxide (CO2) on marine invertebrate behaviour are largely unknown. Marine gastropod conch snails have a modified foot and operculum allowing them to leap backwards rapidly when faced with a predator, such as a venomous cone shell. Here, we show that projected near-future seawater CO2 levels (961 µatm) impair this escape behaviour during a predator-prey interaction. Elevated-CO2 halved the number of snails that jumped from the predator, increased their latency to jump and altered their escape trajectory. Physical ability to jump was not affected by elevated-CO2 indicating instead that decision-making was impaired. Antipredator behaviour was fully restored by treatment with gabazine, a GABA antagonist of some invertebrate nervous systems, indicating potential interference of neurotransmitter receptor function by elevated-CO2, as previously observed in marine fishes. Altered behaviour of marine invertebrates at projected future CO2 levels could have potentially far-reaching implications for marine ecosystems.
The rise in atmospheric CO2 has caused significant decrease in sea surface pH and carbonate ion (CO32-) concentration. This decrease has a negative effect on calcification in hermatypic corals and other calcifying organisms. We report the results of three laboratory experiments designed specifically to separate the effects of the different carbonate chemistry parameters (pH, CO32-, CO2 [aq], total alkalinity [AT], and total inorganic carbon [C T]) on the calcification, photosynthesis, and respiration of the hermatypic coral Acropora eurystoma. The carbonate system was varied to change pH (7.9-8.5), without changing CT; CT was changed keeping the pH constant, and CT was changed keeping the pCO2 constant. In all of these experiments, calcification (both light and dark) was positively correlated with CO32- concentration, suggesting that the corals are not sensitive to pH or CT but to the CO 32- concentration. A decrease of ∼30% in the CO 32- concentration (which is equivalent to a decrease of about 0.2 pH units in seawater) caused a calcification decrease of about 50%. These results suggest that calcification in today's ocean (pCO2 = 370 ppm) is lower by ∼20% compared with preindustrial time (pCO2 = 280 ppm). An additional decrease of ∼35% is expected if atmospheric CO 2 concentration doubles (pCO2 = 560 ppm). In all of these experiments, photosynthesis and respiration did not show any significant response to changes in the carbonate chemistry of seawater. Based on this observation, we propose a mechanism by which the photosynthesis of symbionts is enhanced by coral calcification at high pH when CO2(aq) is low. Overall it seems that photosynthesis and calcification support each other mainly through internal pH regulation, which provides CO32- ions for calcification and CO2(aq) for photosynthesis. © 2006, by the American Society of Limnology and Oceanography, Inc.
A mesocosm experiment was conducted to quantify the effects of short- (2 wk) and long-term (20 wk) exposure to acidified seawater on the structure and diversity of macrofaunal and nematode assemblages in 2 different sediment. types. The impact of acidified seawater on sediment nutrient fluxes was also determined. Using carbon dioxide (CO2) gas, seawater was acidified to pH 7.3 (mimicking ocean acidification), 6.5 or 5.6 (mimicking leakage from a sub-seabed CO2 store site). Control treatments were maintained in natural seawater [pH approximate to 8.0). Exposure to acidified seawater significantly altered community structure and reduced diversity for both macrofaunal and nematode assemblages, However, the impact on nematodes was less severe than that on macrofauna. While the communities in both sediment types were significantly affected by changes in seawater pH, impacts on sandy sediment fauna were greater than those on muddy sediment fauna. Sandy sediments also showed the greatest effects with respect to nutrient fluxes. In sand, the efflux of nitrite, nitrate and silicate decreased in response to increased acidification while the efflux of ammonium increased, In mud, acidification increased the efflux of ammonium but had no effect on the other nutrients. We conclude that both leakage from carbon storage and ocean acidification could cause significant changes in the structure and diversity of coastal sediment communities. Lowered seawater pH could also affect nutrient cycling directly by altering bacterial communities and indirectly through impacts on the abundance and activity of key bioturbators.
Ocean acidification due to anthropogenic CO2
emissions is a dominant driver of long-term changes in pH
in the open ocean, raising concern for the future of calcifying
organisms, many of which are present in coastal habitats.
However, changes in pH in coastal ecosystems result from a
multitude of drivers, including impacts from watershed processes,
nutrient inputs, and changes in ecosystem structure
and metabolism. Interaction between ocean acidification due
to anthropogenic CO2 emissions and the dynamic regional to
local drivers of coastal ecosystems have resulted in complex
regulation of pH in coastal waters. Changes in the watershed
can, for example, lead to changes in alkalinity and CO2 fluxes
that, together with metabolic processes and oceanic dynamics,
yield high-magnitude decadal changes of up to 0.5 units in
coastal pH. Metabolism results in strong diel to seasonal
fluctuations in pH, with characteristic ranges of 0.3 pH units,
with metabolically intense habitats exceeding this range on a
daily basis. The intense variability and multiple, complex
controls on pH implies that the concept of ocean acidification
due to anthropogenic CO2 emissions cannot be transposed to
coastal ecosystems directly. Furthermore, in coastal ecosystems,
the detection of trends towards acidification is not trivial
and the attribution of these changes to anthropogenic CO2
emissions is even more problematic. Coastal ecosystems may
show acidification or basification, depending on the balance
between the invasion of coastal waters by anthropogenic CO2,
watershed export of alkalinity, organic matter and CO2, and
changes in the balance between primary production, respiration
and calcification rates in response to changes in nutrient
inputs and losses of ecosystem components. Hence, we
contend that ocean acidification from anthropogenic CO2 is
largely an open-ocean syndrome and that a concept of anthropogenic
impacts on marine pH, which is applicable across the
entire ocean, from coastal to open-ocean environments,
provides a superior framework to consider the multiple
components of the anthropogenic perturbation of marine
pH trajectories. The concept of anthropogenic impacts on
seawater pH acknowledges that a regional focus is necessary
to predict future trajectories in the pH of coastal
waters and points at opportunities to manage these trajectories
locally to conserve coastal organisms vulnerable to
ocean acidification.
Recent research has shown that exposure to elevated carbon dioxide (CO2) affects how fishes perceive their environment, affecting behavioral and cognitive processes leading to increased prey mortality. However, it is unclear if increased mortality results from changes in the dynamics of predator-prey interactions or due to prey increasing activity levels. Here we demonstrate that ocean pCO2 projected to occur by 2100 significantly effects the interactions of a predator-prey pair of common reef fish: the planktivorous damselfish Pomacentrus amboinensis and the piscivorous dottyback Pseudochromis fuscus. Prey exposed to elevated CO2 (880 µatm) or a present-day control (440 µatm) interacted with similarly exposed predators in a cross-factored design. Predators had the lowest capture success when exposed to elevated CO2 and interacting with prey exposed to present-day CO2. Prey exposed to elevated CO2 had reduced escape distances and longer reaction distances compared to prey exposed to present-day CO2 conditions, but this was dependent on whether the prey was paired with a CO2 exposed predator or not. This suggests that the dynamics of predator-prey interactions under future CO2 environments will depend on the extent to which the interacting species are affected and can adapt to the adverse effects of elevated CO2.
The acrorhagial responses of four sea anemones, Anthopleura krebsi, Bunodosoma cavernata, Anemonia sargassensis, and Anthopleura xanthogrammica, are described. All four acrorhagial responses can be considered forms of aggression. The acrorhagial response is only one of several responses of sea anemones to contact with other animals; others include several methods of avoidance and feeding. Prior experience can influence the acrorhagial response. In A. krebsi, the effect of a prior encounter on the excitation threshold can be seen for at least 2 hr.Interspecific behavioral interactions were examined in A. krebsi, B. cavernata, and A. sargassensis. With one exception, acrorhagial responses were only elicited by contact with some anthozoans. The exception is that some A. krebsi respond to the scyphistomac of the scyphozoan Cassiopea. xamachana. Some C. xamachana medusae from the same clone also elicited acrorhagial expansion and application behavior but never acrorhagial peeling.Intraspecific interactions wer...
Ocean acidification, resulting from rising atmospheric carbon dioxide concentrations, is a pervasive stressor that can affect many marine organisms and their symbionts. Studies which examine the host physiology and microbial communities have shown a variety of responses to the ocean acidification process. Recently, several studies were conducted based on field experiments, which take place in natural CO(2) vents, exposing the host to natural environmental conditions of varying pH. This study examines the sea anemone Anemonia viridis which is found naturally along the pH gradient in Ischia, Italy, with an aim to characterize whether exposure to pH impacts the holobiont. The physiological parameters of A. viridis (Symbiodinium density, protein, and chlorophyll a+c concentration) and its microbial community were monitored. Although reduction in pH was seen to have had an impact on composition and diversity of associated microbial communities, no significant changes were observed in A. viridis physiology, and no microbial stress indicators (i.e., pathogens, antibacterial activity, etc.) were detected. In light of these results, it appears that elevated CO(2) does not have a negative influence on A. viridis that live naturally in the site. This suggests that natural long-term exposure and dynamic diverse microbial communities may contribute to the acclimation process of the host in a changing pH environment.
One of the greatest sources of uncertainty for future climate predictions is the response of the global carbon cycle to climate change. Although approximately one-half of total CO(2) emissions is at present taken up by combined land and ocean carbon reservoirs, models predict a decline in future carbon uptake by these reservoirs, resulting in a positive carbon-climate feedback. Several recent studies suggest that rates of carbon uptake by the land and ocean have remained constant or declined in recent decades. Other work, however, has called into question the reported decline. Here we use global-scale atmospheric CO(2) measurements, CO(2) emission inventories and their full range of uncertainties to calculate changes in global CO(2) sources and sinks during the past 50 years. Our mass balance analysis shows that net global carbon uptake has increased significantly by about 0.05 billion tonnes of carbon per year and that global carbon uptake doubled, from 2.4 ± 0.8 to 5.0 ± 0.9 billion tonnes per year, between 1960 and 2010. Therefore, it is very unlikely that both land and ocean carbon sinks have decreased on a global scale. Since 1959, approximately 350 billion tonnes of carbon have been emitted by humans to the atmosphere, of which about 55 per cent has moved into the land and oceans. Thus, identifying the mechanisms and locations responsible for increasing global carbon uptake remains a critical challenge in constraining the modern global carbon budget and predicting future carbon-climate interactions.
The biodiversity of coral reefs is dominated by invertebrates. Many of these invertebrates live in close association with scleractinian corals, relying on corals for food, habitat or settlement cues. Given their strong dependence on corals, it is of great concern that our knowledge of coral-associated invertebrates is so limited, especially in light of severe and ongoing degradation of coral reef habitats and the potential for species extinctions. This review examines the taxonomic extent of coral-associated invertebrates, the levels of dependence on coral hosts, the nature of associations between invertebrates and corals, and the factors that threaten coral-associated invertebrates now and in the future. There are at least 860 invertebrate species that have been described as coral asso-ciated, of which 310 are decapod crustaceans. over half of coral-associated invertebrates appear to have an obligate dependence on live corals. Many exhibit a high degree of preference for one or two coral species, with species in the genera Pocillopora, Acropora and Stylophora commonly pre-ferred. This level of habitat specialization may place coral-associated invertebrates at a great risk of extinction, particularly because preferred coral genera are those most susceptible to coral bleaching and mortality. In turn, many corals are also reliant on the services of particular invertebrates, lead-ing to strong feedbacks between abundance of corals and their associated invertebrates. The loss of even a few preferred coral taxa could lead to a substantial decline in invertebrate biodiversity and have far-reaching effects on coral reef ecosystem function. A full appreciation of the consequences of further coral reef degradation for invertebrate biodiversity awaits a more complete description of the diversity of coral-associated invertebrates, the roles they play in coral reef ecosystems, their contribution to reef resilience and their conservation needs.
Contest behavior, where individuals compete directly against one another for access to limited resources, is widespread across animal taxa. In many cases, contests are settled though the use of noninjurious behavior such as agonistic signals and even fights that involve weapons are often resolved through processes of assessment and strategic decision making. Here, we determine the role of these "decision rules" during staged contests in a simple animal, the beadlet sea anemone Actinia equina using a recently suggested approach of analyzing 1) traits linked to resource holding potential (RHP), 2) relationships between RHP and contest duration, and 3) contest dynamics. Depending on the activities used in the encounter, RHP, is linked to overall body size, the size of stinging nematocyst weapons, or by the ability to land blows on the opponent. Furthermore, changes in the intensity of aggression as the contest progresses indicate the use of 2 distinct types of self-assessment-based decision rules, which differ according to whether weapons are used in the contest. Therefore, these fights in animals that lack a centralized nervous system appear to involve the use of logical decision rules similar to those observed in contests in animals that are often assumed to be more "complex" in their behavior. Indeed, anemones appear to use different sources of information about incurred costs, depending on the intensity of the contest. Copyright 2011, Oxford University Press.
Samples of apparently similar red morphs of the common beadlet sea anemone Actinia equina (L.) were collected from rocky shores on the Isle of Man (Irish Sea), on the French Mediterranean coast near Marseille and
on the Cape Verde Island of Sal (off West Africa). For additional comparison an orange morph and the green A. prasina were also collected from the Isle of Man. Morphological descriptions were made and the samples were compared by nematocyst
analysis and enzyme electrophoresis. The three British samples showed little genetic divergence (I>0.90) but the Mediterranean sample was hugely divergent (I<0.20) from the British ones. The Cape Verde Island anemones were also very different (I<0.60) from all other samples. It is concluded that the red morph samples from the Cape Verde Islands, the Mediterranean and
the Isle of Man belong to three different species. For the new species from the Mediterranean and Cape Verde Islands formal
descriptions are given, and the names Actinia schmidti sp.n. and Actinia sali sp.n. are proposed.
Competition among sessile organisms is a major process on coral reefs, and is becoming more important as anthropogenic disturbances
cause shifts in dominance to non-reef builders such as macroalgae, soft corals, ascidians, and corallimorpharians. Long-term
monitoring and field experiments have demonstrated that competition for limited space can exert major impacts on reef biodiversity
and community composition across habitats and regions. Recent experiments also reveal increasingly important roles of allelopathic
chemicals and the alteration of associated microbes in shaping competitive outcomes among benthic space occupiers. Competition
impacts the recruitment, growth, and mortality of sessile reef organisms and alters their population dynamics. Co-settlement
and aggregation of conspecific coral colonies may lead to intense intraspecific competition, including chimera formation and
potential somatic and germ cell parasitism. The complexity of competitive outcomes and their alteration by a wide variety
of factors, including irradiance, water motion, and nutrient levels, results in mostly circular networks of interaction, often
enhancing species diversity on coral reefs. Competition is a model process for revealing impacts of human activities on coral
reefs, and will become increasingly important as alternate dominants gain space at the expense of reef-building corals.
KeywordsInterference competition-exploitation competition-competition-cnidarian-macroalgae-cyanobacteria-scleractinian-corallimorpharian-actinarian-sea anemone-ascidian-zoanthid-fungiid-hydrocoral-octocoral-soft coral-stony coral-coral-sponge-climate change-chimera-growth-mortality-reproduction-competitive network-coral–algal interaction-phase shift-feedback loop-model-allelopathy-herbivory-recruitment-antibiotic-microorganism-bacteria-abrasion-palytoxin-bleaching-disease-natural products-nematocyst-mucus-diversity-community structure-aggression-population-alternate dominant
Some photosynthetic organisms benefit from elevated levels of
carbon dioxide, but studies on the effects of elevated PCO2 on
the algal symbionts of animals are very few. This study
investigated the impact of hypercapnia on a photosynthetic
symbiosis between the anemone Anthopleura elegantissima and
its zooxanthella Symbiodinium muscatinei. Anemones were
maintained in the laboratory for 1 week at 37 Pa PCO2 and
pH 8.1. Clonal pairs were then divided into two groups and
maintained for 6 weeks under conditions naturally experienced
in their intertidal environment, 45 Pa PCO2, pH 8.1 and
231 Pa PCO2, pH 7.3. Respiration and photosynthesis were
measured after the 1-week acclimation period and after 6
weeks in experimental conditions. Density of zooxanthellal
cells, zooxanthellal cell size, mitotic index and chlorophyll
content were compared between non-clonemate anemones
after the 1-week acclimation period and clonal anemones at the
end of the experiment. Anemones thrived in hypercapnia.
After 6 weeks, A. elegantissima exhibited higher rates of
photosynthesis at 45 Pa (4.2 mmol O2 g21 h21) and 231 Pa
(3.30 mmol O2 g21 h21) than at the initial 37 Pa (1.53 mmol O2
g21 h21). Likewise, anemones at 231 Pa received more of their
respiratory carbon from zooxanthellae (CZAR 578.2%) than
those at 37 Pa (CZAR 566.6%) but less than anemones at
45 Pa (CZAR 5137.3%). The mitotic index of zooxanthellae
was significantly greater in the hypercapnic anemones than in
anemones at lower PCO2. Excess zooxanthellae were expelled
by their hosts, and cell densities, cell diameters and chlorophyll
contents were not significantly different between the groups.
The response of A. elegantissima to hypercapnic acidification
reveals the potential adaptation
The initial response of individuals to human-induced environmental change is often behavioural. This can improve the performance of individuals under sudden, large-scale perturbations and maintain viable populations. The response can also give additional time for genetic changes to arise and, hence, facilitate adaptation to new conditions. On the other hand, maladaptive responses, which reduce individual fitness, may occur when individuals encounter conditions that the population has not experienced during its evolutionary history, which can decrease population viability. A growing number of studies find human disturbances to induce behavioural responses, both directly and by altering factors that influence fitness. Common causes of behavioural responses are changes in the transmission of information, the concentration of endocrine disrupters, the availability of resources, the possibility of dispersal, and the abundance of interacting species. Frequent responses are alterations in habitat choice, movements, foraging, social behaviour and reproductive behaviour. Behavioural responses depend on the genetically determined reaction norm of the individuals, which evolves over generations. Populations first respond with individual behavioural plasticity, whereafter changes may arise through innovations and the social transmission of behavioural patterns within and across generations, and, finally, by evolution of the behavioural response over generations. Only a restricted number of species show behavioural adaptations that make them thrive in severely disturbed environments. Hence, rapid human-induced disturbances often decrease the diversity of native species, while facilitating the spread of invasive species with highly plastic behaviours. Consequently, behavioural responses to human-induced environmental change can have profound effects on the distribution, adaptation, speciation and extinction of populations and, hence, on biodiversity. A better understanding of the mechanisms of behavioural responses and their causes and consequences could improve our ability to predict the effects of human-induced environmental change on individual species and on biodiversity.
The usefulness and generality of the keystone species concept has recently been questioned. We investigated variation in interaction strength between the original keystone predator, the seastar Pisaster ochraceus, and its primary prey (Mytilus californianus and M.trossulus). The study was prompted by differences in community structure at two low zone sites along the central Oregon coast, Boiler Bay(BB) and Strawberry Hill(SH). Predators, especially seastars, were larger and more abundant at SH than at BB. Further, sessile animals were more abundant and macrophytes less abundant at SH. Predators were more abundant at wave--exposed sites at both sites, and at SH, sessile invertebrates were more abundant at the wave--exposed location and sand cover was high at the wave-protected location. To test the hypothesis that variation in predation strength explained some of the differences, we examined the seastar--mussel interaction at locations with high & low wave exposure at both sites. Predation intensity was quantified by determining the survival of mussels in clumps(50 mussels per clump, shell length 4--7cm) transplanted to large plots(18-163m2)with or without seastars in the low intertidal zone. Predation effects were quantified by determining prey recolonisation rates in marked quadrats in the same large plots. Spatial variation in interaction strength was quantified by examining predation at scales of metres(among transplants within plots), 10's of metres(between replicate plots within each exposure at each site). , 100's of metres(between wave exposures within locations), and 10,000's of metres (between sites). Temporal variation was evaluated by performing the experiments in 1990 and 1991. The relation between prey(mussel) recruitment and growth to differences in community structure was evaluated by quantifying recruitment density in plastic mesh balls(collectors) and growth of individually marked transplanted mussels, respectively, at each site' exposure' tide level combination each month for 4years. Predation intensity varied at all spatial scales. At the two largest spatial scales(10's of kilometres, 100's of metres), differences in both survival of transplanted mussels and prey recolonisation depended on variation in seastar abundance with site, wave exposure, prey recruitment and growth, and at SH protected, the extent of sand burial. Variation at the two smallest scales(metres, 10's of metres) was high when seastars were scarce and low when seastars were abundant. Transplanted mussels suffered 100% mortality in 2 weeks at wave--exposed SH, but took >52weeks at wave--protected BB. Seastar effects on recolonisation were detected only at the SH wave--exposed site. Here, where prey recruitment and growth were unusually high, the mussel M.trossulus invaded and dominated space within 9months. After 14 months, whelks, which increased in both size and abundance in the absence of Pisaster, arrested this increase in mussel abundance. Similar changes did not occur at other site' exposure combinations, evidently because prey recruitment was low and possibly also due to whelk predation on juveniles. Longer-term results indicate that, as in Washington State, seastars prevent large adult M.californianus from invading lower intertidal regions, but only at wave--exposed, not wave--protected sites. Thus, three distinct predation regimes were observed:
1) strong keystone predation by seastars at wave--exposed headlands
2) less-strong diffuse predation by seastars, whelks, and possibly other predators at wave--protected cove, and
3) weak predation at a wave-protected site buried regularly by sand.
Comparable experimental results at four-wave-exposed headlands(our two in Oregon and two others in Washington), and similarities between these and communities on other West Coast headlands suggest that keystone predation occurs broadly in this system. Results in wave-protected habitats, however, suggest that it is not universal. In Oregon, keystone predation was evidently contingent on conditions of high prey production(i.e. recruitment & growth), while diffuse predation occurred when prey production was low, and weak predation occurred when environmental stress was high.
Combining our results with examples from other marine and non-marine habitats suggests a need to consider a broader range of models than just keystone predation. The predictive and explanatory value of an expanded set of models depends on identifying factors distinguishing them. Although evidence is limited, a survey of 17 examples suggests
1) keystone predation is evidently not distinguished from diffuse predation by any of 11 previously proposed differences, but
2) may be distinguished by rates of prey production. Further,
3) differential predation on competitively dominant prey does not distinguish keystone from non-keystone systems, since this interaction occurs in both types of communities
Instead, differential predation on dominant prey evidently distinguishes strong--from weak--predation communities. While the keystone predation concept has been and will continue to be useful, a broadened focus on testing and developing a more general models of community regulation is needed.
Ocean acidification resulting from human emissions of carbon dioxide has already lowered and will further lower surface ocean pH. The consequent decrease in calcium carbonate saturation potentially threatens calcareous marine organisms. Here, we demonstrate that the calcification rates of the edible mussel (Mytilus edulis) and Pacific oyster (Crassostrea gigas) decline linearly with increasing pCO2. Mussel and oyster calcification may decrease by 25 and 10%, respectively, by the end of the century, following the IPCC IS92a scenario (∼740 ppmv in 2100). Moreover, mussels dissolve at pCO2 values exceeding a threshold value of ∼1800 ppmv. As these two species are important ecosystem engineers in coastal ecosystems and represent a large part of worldwide aquaculture production, the predicted decrease of calcification in response to ocean acidification will probably have an impact on coastal biodiversity and ecosystem functioning as well as potentially lead to significant economic loss.
Contest theory predicts the evolution of a stable mixture of different strategies for fighting. Here, we investigate the possibility that stable between-individual differences in startle-response durations influence fighting ability or 'resource-holding potential' (RHP) in the beadlet sea anemone, Actinia equina. Both winners and losers showed significant repeatability of pre-fight startle-response durations but mean pre-fight startle-response durations were greater for eventual losers than for eventual winners, indicating that RHP varies with boldness. In particular, individuals with short startle responses inflicted more attacks on their opponent. Both repeatability and mean-level responses were changed by the experience of fighting, and these changes varied with outcome. In losers, repeatability was disrupted to a greater extent and the mean startle-response durations were subject to a greater increase than in winners. Thus, following a fight, this behavioural correlate of RHP behaves in a way similar to post-fight changes in physiological status, which can also vary between winners and losers. Understanding the links between aggression and boldness therefore has the potential to enhance our understanding of both the evolution of animal personality and the 'winner and loser effects' of post-fight changes in RHP.
Changes in olfactory-mediated behaviour caused by elevated CO(2) levels in the ocean could affect recruitment to reef fish populations because larval fish become more vulnerable to predation. However, it is currently unclear how elevated CO(2) will impact the other key part of the predator-prey interaction--the predators. We investigated the effects of elevated CO(2) and reduced pH on olfactory preferences, activity levels and feeding behaviour of a common coral reef meso-predator, the brown dottyback (Pseudochromis fuscus). Predators were exposed to either current-day CO(2) levels or one of two elevated CO(2) levels (∼600 µatm or ∼950 µatm) that may occur by 2100 according to climate change predictions. Exposure to elevated CO(2) and reduced pH caused a shift from preference to avoidance of the smell of injured prey, with CO(2) treated predators spending approximately 20% less time in a water stream containing prey odour compared with controls. Furthermore, activity levels of fish was higher in the high CO(2) treatment and feeding activity was lower for fish in the mid CO(2) treatment; indicating that future conditions may potentially reduce the ability of the fish to respond rapidly to fluctuations in food availability. Elevated activity levels of predators in the high CO(2) treatment, however, may compensate for reduced olfactory ability, as greater movement facilitated visual detection of food. Our findings show that, at least for the species tested to date, both parties in the predator-prey relationship may be affected by ocean acidification. Although impairment of olfactory-mediated behaviour of predators might reduce the risk of predation for larval fishes, the magnitude of the observed effects of elevated CO(2) acidification appear to be more dramatic for prey compared to predators. Thus, it is unlikely that the altered behaviour of predators is sufficient to fully compensate for the effects of ocean acidification on prey mortality.
Ocean acidification is predicted to affect marine ecosystems in many ways, including modification of fish behaviour. Previous studies have identified effects of CO(2)-enriched conditions on the sensory behaviour of fishes, including the loss of natural responses to odours resulting in ecologically deleterious decisions. Many fishes also rely on hearing for orientation, habitat selection, predator avoidance and communication. We used an auditory choice chamber to study the influence of CO(2)-enriched conditions on directional responses of juvenile clownfish (Amphiprion percula) to daytime reef noise. Rearing and test conditions were based on Intergovernmental Panel on Climate Change predictions for the twenty-first century: current-day ambient, 600, 700 and 900 µatm pCO(2). Juveniles from ambient CO(2)-conditions significantly avoided the reef noise, as expected, but this behaviour was absent in juveniles from CO(2)-enriched conditions. This study provides, to our knowledge, the first evidence that ocean acidification affects the auditory response of fishes, with potentially detrimental impacts on early survival.
Ocean acidification (OA) refers to the ongoing decline in oceanic pH resulting from the uptake of atmospheric CO(2). Mounting experimental evidence suggests that OA will have negative consequences for a variety of marine organisms. Whereas the effect of OA on the calcification of adult reef corals is increasingly well documented, effects on early life history stages are largely unknown. Coral recruitment, which necessitates successful fertilization, larval settlement, and postsettlement growth and survivorship, is critical to the persistence and resilience of coral reefs. To determine whether OA threatens successful sexual recruitment of reef-building corals, we tested fertilization, settlement, and postsettlement growth of Acropora palmata at pCO(2) levels that represent average ambient conditions during coral spawning (∼400 μatm) and the range of pCO(2) increases that are expected to occur in this century [∼560 μatm (mid-CO(2)) and ∼800 μatm (high-CO(2))]. Fertilization, settlement, and growth were all negatively impacted by increasing pCO(2), and impairment of fertilization was exacerbated at lower sperm concentrations. The cumulative impact of OA on fertilization and settlement success is an estimated 52% and 73% reduction in the number of larval settlers on the reef under pCO(2) conditions projected for the middle and the end of this century, respectively. Additional declines of 39% (mid-CO(2)) and 50% (high-CO(2)) were observed in postsettlement linear extension rates relative to controls. These results suggest that OA has the potential to impact multiple, sequential early life history stages, thereby severely compromising sexual recruitment and the ability of coral reefs to recover from disturbance.
Ecology Letters (2010) 13: 1419–1434
Abstract
Ocean acidification is a pervasive stressor that could affect many marine organisms and cause profound ecological shifts. A variety of biological responses to ocean acidification have been measured across a range of taxa, but this information exists as case studies and has not been synthesized into meaningful comparisons amongst response variables and functional groups. We used meta‐analytic techniques to explore the biological responses to ocean acidification, and found negative effects on survival, calcification, growth and reproduction. However, there was significant variation in the sensitivity of marine organisms. Calcifying organisms generally exhibited larger negative responses than non‐calcifying organisms across numerous response variables, with the exception of crustaceans, which calcify but were not negatively affected. Calcification responses varied significantly amongst organisms using different mineral forms of calcium carbonate. Organisms using one of the more soluble forms of calcium carbonate (high‐magnesium calcite) can be more resilient to ocean acidification than less soluble forms (calcite and aragonite). Additionally, there was variation in the sensitivities of different developmental stages, but this variation was dependent on the taxonomic group. Our analyses suggest that the biological effects of ocean acidification are generally large and negative, but the variation in sensitivity amongst organisms has important implications for ecosystem responses.
Climate change, rising atmospheric carbon dioxide, excess nutrient inputs, and pollution in its many forms are fundamentally
altering the chemistry of the ocean, often on a global scale and, in some cases, at rates greatly exceeding those in the historical
and recent geological record. Major observed trends include a shift in the acid-base chemistry of seawater, reduced subsurface
oxygen both in near-shore coastal water and in the open ocean, rising coastal nitrogen levels, and widespread increase in
mercury and persistent organic pollutants. Most of these perturbations, tied either directly or indirectly to human fossil
fuel combustion, fertilizer use, and industrial activity, are projected to grow in coming decades, resulting in increasing
negative impacts on ocean biota and marine resources.
Predictions about the ecological consequences of oceanic uptake of CO(2) have been preoccupied with the effects of ocean acidification on calcifying organisms, particularly those critical to the formation of habitats (e.g. coral reefs) or their maintenance (e.g. grazing echinoderms). This focus overlooks the direct effects of CO(2) on non-calcareous taxa, particularly those that play critical roles in ecosystem shifts. We used two experiments to investigate whether increased CO(2) could exacerbate kelp loss by facilitating non-calcareous algae that, we hypothesized, (i) inhibit the recovery of kelp forests on an urbanized coast, and (ii) form more extensive covers and greater biomass under moderate future CO(2) and associated temperature increases. Our experimental removal of turfs from a phase-shifted system (i.e. kelp- to turf-dominated) revealed that the number of kelp recruits increased, thereby indicating that turfs can inhibit kelp recruitment. Future CO(2) and temperature interacted synergistically to have a positive effect on the abundance of algal turfs, whereby they had twice the biomass and occupied over four times more available space than under current conditions. We suggest that the current preoccupation with the negative effects of ocean acidification on marine calcifiers overlooks potentially profound effects of increasing CO(2) and temperature on non-calcifying organisms.
The biodiversity of coral reefs is dominated by invertebrates. Many of these invertebrates live in close association with scleractinian corals, relying on corals for food, habitat or settlement cues. Given their strong dependence on corals, it is of great concern that our knowledge of coralassociated invertebrates is so limited, especially in light of severe and ongoing degradation of coral reef habitats and the potential for species extinctions. This review examines the taxonomic extent of coral-associated invertebrates, the levels of dependence on coral hosts, the nature of associations between invertebrates and corals, and the factors that threaten coral-associated invertebrates now and in the future. There are at least 860 invertebrate species that have been described as coral associated, of which 310 are decapod crustaceans. Over half of coral-associated invertebrates appear to have an obligate dependence on live corals. Many exhibit a high degree of preference for one or two coral species, with species in the genera Pocillopora, Acropora and Stylophora commonly preferred. This level of habitat specialization may place coral-associated invertebrates at a great risk of extinction, particularly because preferred coral genera are those most susceptible to coral bleaching and mortality. In turn, many corals are also reliant on the services of particular invertebrates, leading to strong feedbacks between abundance of corals and their associated invertebrates. The loss of even a few preferred coral taxa could lead to a substantial decline in invertebrate biodiversity and have far-reaching effects on coral reef ecosystem function. A full appreciation of the consequences of further coral reef degradation for invertebrate biodiversity awaits a more complete description of the diversity of coral-associated invertebrates, the roles they play in coral reef ecosystems, their contribution to reef resilience and their conservation needs. © R. N. Gibson, R. J. A. Atkinson, J. D. M. Gordon, I. P. Smith and D. J. Hughes, Editors Taylor & Francis. All rights reserved.
1. The pH range for normal embryonic development of oysters was 6.75 to 8.75, and for clams, 7.00 to 8.75.2. More than 68% of the larvae of both clams and oysters survived at pH 6.25 to 8.75. The lower pH limit for survival of oyster larvae was 6.00 and for clam larvae, 6.25.3. The pH range for normal growth was 6.75 to 8.50 for clam larvae and 6.75 to 8.75 for oyster larvae. The rate of growth of both species dropped rapidly at pH levels below 6.75.4. The optimum pH for growth was 7.50 to 8.00 for clam larvae and 8.25 to 8.50 for oyster larvae.5. At pH 9.00 to 9.50 the percentage of eggs that developed normally, the percentage of larvae that survived, and the percentage increase in mean length of both species decreased rapidly.
Pairwise contests occur when two individuals compete directly over ownership of an indivisible resource. Contests vary in the degree of escalation, some encounters being settled through non-injurious behaviour while others are only resolved after dangerous fighting. Here, we investigate the role of relatedness, assessed using AFLP analysis, on the occurrence of stinging during staged contests in the beadlet sea anemone Actinia equina. Contrary to our expectations, we found that the chance of stinging, and hence the chance of inflicting damage, increased with the degree of relatedness between the two opponents. This result may be explained by the negative relationship between asymmetry in fighting ability and escalation level predicted by theory. We suggest that in order to fully understand how relatedness influences aggression, predictions from kin selection theory should be incorporated with those from contest theory.
The effects of oil pollution on the sea anemone Actinia equina were investigated. Chronic pollution with 2.5 ml.l−1 crude oil resulted, for about seven weeks, in ejection of increased numbers of the young which are normally brooded within the gastric cavity. Subsequently the numbers of surviving young being produced fell to zero, and the ovaries were found to be regressed and lacking ova. The anemones were also more frequently observed with tentacles expanded and mouth open, but the response to food offered to the tentacles was slow or absent. In separate tests it was found that crude oil presented on filter paper to the anemones could act as a feeding inducer, but that it interfered with or diluted the action of natural feeding inducers present in fish muscle extract. These effects are comparable with those which oil pollution has been found by other workers to have upon other anthozoans—the corals.
The decisions that animals make are based on information gathered from their environment, and can have consequences for their fitness and survival. Such processes can be disrupted by environmental change. Hermit crabs find and select the gastropod shells they inhabit using chemical and visual cues, and tactile assessment. The choice of an optimal shell is important since it provides shelter against environmental extremes and protection against predators; inhabiting a suboptimal shell can also reduce fecundity. Hermit crabs are subject to cyclical reductions in the pH of the water in the intertidal rock pools that they inhabit, and such reductions may be further exacerbated by climate change. Reduced sea water pH, a consequence of ocean acidification and leaks from geological storage sites, has already been shown to disrupt the behaviour of marine animals. We investigated the effects of reduced sea water pH on the shell assessment and selection behaviour of the hermit crab Pagurus bernhardus. Under highly reduced pH conditions (pH 6.8) crabs were less likely to change from a suboptimal to an optimal shell than those in untreated sea water; those that did change shells took longer to do so. Crabs in the reduced pH treatment also showed significantly lower antennular flicking rates (the ‘sniffing’ response in decapods) and reduced movement. Thus, a reduction in sea water pH disrupts the resource assessment and decision-making processes of these crabs, indicating that the ability to acquire a vital resource may be influenced by both naturally occurring environmental cycles and anthropogenically induced environmental change.
Increased seawater pCO 2 , and in turn 'ocean acidification' (OA), is predicted to profoundly impact marine ecosystem diversity and function this century. Much research has already focussed on calcifying reef-forming corals (Class: Anthozoa) that appear particularly susceptible to OA via reduced net calcification. However, here we show that OA-like conditions can simultaneously enhance the ecological success of non-calcifying anthozoans, which not only play key ecological and biogeochemical roles in present day benthic ecosystems but also represent a model organism should calcifying anthozoans exist as less calcified (soft-bodied) forms in future oceans. Increased growth (abundance and size) of the sea anemone (Anemonia viridis) population was observed along a natural CO 2 gradient at Vulcano, Italy. Both gross photosynthesis (P G) and respiration (R) increased with pCO 2 indicating that the increased growth was, at least in part, fuelled by bottom up (CO 2 stimulation) of metabolism. The increase of P G outweighed that of R and the genetic identity of the symbiotic microalgae (Symbiodinium spp.) remained unchanged (type A19) suggesting proximity to the vent site relieved CO 2 limitation of the anemones' symbiotic microalgal population. Our observa-tions of enhanced productivity with pCO 2 , which are consistent with previous reports for some calcifying corals, con-vey an increase in fitness that may enable non-calcifying anthozoans to thrive in future environments, i.e. higher seawater pCO 2 . Understanding how CO 2 -enhanced productivity of non-(and less-) calcifying anthozoans applies more widely to tropical ecosystems is a priority where such organisms can dominate benthic ecosystems, in particular following localized anthropogenic stress.
Exposure to pollution and environmental change can alter the behaviour of aquatic animals and here we review recent evidence that exposure to elevated CO₂ and reduced sea water pH alters the behaviour of tropical reef fish and hermit crabs. Three main routes through which behaviour might be altered are discussed; elevated metabolic load, 'info-disruption' and avoidance behaviour away from polluted locations. There is clear experimental evidence that exposure to high CO₂ disrupts the ability to find settlement sites and shelters, the ability to detect predators and the ability to detect prey and food. In marine vertebrates and marine crustaceans behavioural change appears to occur via info-disruption. In hermit crabs and other crustaceans impairment of performance capacities might also play a role. We discuss the implications for such behavioural changes in terms of potential impacts at the levels of population health and ecosystem services, and consider future directions for research.
Our planet is experiencing an increase in the concentration of atmospheric carbon dioxide (CO2) unprecedented in the past 800 000 years. About 30% of excess atmospheric CO2 is absorbed by the oceans, thus increasing the concentration of carbonic acid and reducing the ocean's pH. Species able to survive the physiological stress imposed by ocean acidification may still suffer strong indirect negative consequences. Comparing the tolerance of different species to dissolved CO2 is a necessary first step towards predicting the ecological impacts of rising CO2 levels on marine communities. While it is intuitive that not all aquatic species will be affected the same way by CO2, one could predict that closely related species, sharing similar life histories and ecology, may show similar tolerance levels to CO2. Our ability to create functional groups of species according to their CO2 tolerance may be crucial in our ability to predict community change in the future. Here, we tested the effects of CO2 exposure on the antipredator responses of four damselfish species (Pomacentrus chrysurus, Pomacentrus moluccensis, Pomacentrus amboinensis and Pomacentrus nagasakiensis). Although being sympatric and sharing the same ecology and life history, the four congeneric species showed striking and unexpected variation in CO2 tolerance, with CO2-induced loss of response to predation risk ranging from 30% to 95%. Using P. chrysurus as a model species, we further tested if these behavioural differences translated into differential ability to survive predators under natural conditions. Our results indicate that P. chrysurus larvae raised under CO2 levels predicted by 2070 and 2100 showed decreased antipredator responses to risk, leading to a five- to sevenfold increase in predation-related mortality in the first few hours of settlement. Examining ocean acidification, along with other environmental variables, will be a critical step in further evaluating ecological responses to predicted climatic change.
The feeding habits of the Mediterranean sea anemonesCereus pedunculatus, Actinia equina andAnemonia viridis were examined mainly by analysing their coelenteron contents. The three species are opportunistic omnivorous suspension feeders.
Main source of food forA. viridis andC. pedunculatus are crustaceans (mainly amphipods and decapods, respectively), while for the midlittoral speciesA. equina, it is organic detritus. Using the same method, the temporal and spatial changes in the diet ofA. viridis were examined. During the whole year, crustaceans seem to be the main source of food forA. viridis. The diet composition of this species, however, differs remarkably in space, possibly reflecting the different composition
of the macrobenthic organismic assemblages in different areas. The data collected are compared with the limited bibliographical
information.
To function as an effective method to avoid build-up of anthropogenic carbon dioxide (CO2) in the atmosphere, storage of CO2 in geologic repositories must be designed and operated to minimize leakage. The design objectives include the obvious requirement to avoid large sudden releases and the more challenging task of keeping long-term leak rates to de minimis levels. Long-term retention requirements are a function of both the atmospheric stabilization target for greenhouse gases and the degree of reliance on CO2 capture and storage as a mitigation measure. A robust strategy will employ the CO2 capture and storage method as a component of a portfolio of programs that emphasize energy efficiency and use of renewable energy. To preserve options to stabilize greenhouse gases at prudent levels, it appears we will need to rely extensively on all three components of this portfolio. In developing criteria for management of leakage from geologic repositories, the policy and technical community will need to engage with environmental groups and the public at the earliest possible point in the process.
Underground storage of industrial quantities of carbon dioxide in porous and permeable reservoir rocks has been taking place for the last 5 years at the Sleipner West gas field in the North Sea. Although there is still significant uncertainty in the actual figures, it appears that globally there is enough underground storage capacity for CO2 to make a significant impact on global emissions to the atmosphere. Some of the major issues that must be addressed if this technology is to spread to industrial plant such as power stations, and thus make an impact on global CO2 emissions, are cost of CO2 capture, demonstration of safety and security of storage and public acceptability.
Fabry, V. J., Seibel, B. A., Feely, R. A., and Orr, J. C. 2008. Impacts of ocean acidification on marine fauna and ecosystem
processes. – ICES Journal of Marine Science, 65: 414–432.
Oceanic uptake of anthropogenic carbon dioxide (CO2) is altering the seawater chemistry of the world’s oceans with consequences for marine biota. Elevated partial pressure of
CO2 (pCO2) is causing the calcium carbonate saturation horizon to shoal in many regions, particularly in high latitudes and regions
that intersect with pronounced hypoxic zones. The ability of marine animals, most importantly pteropod molluscs, foraminifera,
and some benthic invertebrates, to produce calcareous skeletal structures is directly affected by seawater CO2 chemistry. CO2 influences the physiology of marine organisms as well through acid-base imbalance and reduced oxygen transport capacity.
The few studies at relevant pCO2 levels impede our ability to predict future impacts on foodweb dynamics and other ecosystem processes. Here we present new
observations, review available data, and identify priorities for future research, based on regions, ecosystems, taxa, and
physiological processes believed to be most vulnerable to ocean acidification. We conclude that ocean acidification and the
synergistic impacts of other anthropogenic stressors provide great potential for widespread changes to marine ecosystems.
While ocean acidification is predicted to threaten marine biodiversity, the processes that directly impact species persistence are not well understood. For marine species, early life history stages are inherently vulnerable to predators and an innate ability to detect predators can be critical for survival. However, whether or not acidification inhibits predator detection is unknown. Here, we show that newly hatched larvae of the marine fish Amphiprion percula innately detect predators using olfactory cues and this ability is retained through to settlement. Aquarium-reared larvae, not previously exposed to predators, were able to distinguish between the olfactory cues of predatory and non-predatory species. However, when eggs and larvae were exposed to seawater simulating ocean acidification (pH 7.8 and 1000 p.p.m. CO2) settlement-stage larvae became strongly attracted to the smell of predators and the ability to discriminate between predators and non-predators was lost. Newly hatched larvae were unaffected by CO2 exposure and were still able to distinguish between predatory and non-predatory fish. If this impairment of olfactory preferences in settlement-stage larvae translates to higher mortality as a result of increased predation risk, there could be direct consequences for the replenishment and the sustainability of marine populations.
Ecology Letters (2010) 13: 68–75