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Community structure in the four experimental treatments (control, fertilized, caged, fertilized and caged) in March 2000 at the end of 13 months of manipulation. Data shown are the mean values for each functional group which are defined in the text (see Fig. 2 for SE)
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While climate change and associated increases in sea surface temperature and ocean acidification, are among the most important global stressors to coral reefs, overfishing and nutrient pollution are among the most significant local threats. Here we examined the independent and interactive effects of reduced grazing pressure and nutrient enrichment...
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Despite the great ecological importance of coral reefs, they are under threat due to both natural and anthropogenic causes. When communities are located close to the coast, intensified human activity including pollution, overfishing, indiscriminate extraction, and deforestation of associated terrestrial ecosystems can destabilize a coral ecosystem,...
![Experiment 2. The final a algal turf biomass [organic carbon (OC)] and...](profile/Steven-Purcell-2/publication/326815340/figure/fig3/AS:960074805694485@1605911079743/Experiment-2-The-final-a-algal-turf-biomass-organic-carbon-OC-and-b-nitrogen_Q320.jpg)
Coral reefs around the world are changing rapidly, with overfishing of herbivorous fishes and increased sediment inputs being two of the major local-scale stressors. We therefore assessed the effects of sediment loads and overfishing on the nutritional quality and yield to grazing fishes of algal turfs, within the epilithic algal matrix, on a coral...
The Coral Triangle contains the most species-diverse coral reefs in the world, and at its center is the Raja Ampat archipelago in West Papua, Indonesia. The marine resources of Raja Ampat are an important source of food and livelihood for thousands of people, but overfishing and destructive fishing practices threaten its coral reefs and fisheries....
Global and local anthropogenic stressors such as climate change, acidification, overfishing, and pollution are expected to shift the benthic community composition of coral reefs from dominance by calcifying organisms to dominance by non‐calcifying algae. These changes could reduce the ability of coral reef ecosystems to maintain positive net calciu...
A variety of human activities have led to the recent global decline of reef-building corals. The ecological, social, and economic value of coral reefs has made them an international conservation priority. The success of Marine Protected Areas (MPAs) in restoring fish populations has led to optimism that they could also benefit corals by indirectly...
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... There are also instances of natural and healthy native algae-dominated reefs with low coral cover [6]. Two important factors that can cause a coral-dominated or macroalgae-dominated habitat are herbivore activity and nutrient levels [7][8][9][10]. Anthropogenic activities have changed these drivers by decreasing herbivory with fishing pressure and increasing nutrients with land-based sources of pollution [1,5,7]. ...
... The L. variegata we sampled is usually found on shaded surfaces and was found growing adjacent to the turf we sampled. Turf algae are a common component of Hawaiian reef ecosystems but their cover fraction is highly variable with estimates ranging from 5-60% [10]. The complex makeup of turf algae that may cause misclassification of species is an important consideration for reef-scale mapping using spectral signatures and warrants more study. ...
In Hawaiʻi, native macroalgae or “limu” are of ecological, cultural, and economic value. Invasive algae threaten native macroalgae and coral, which serve a key role in the reef ecosystem. Spectroscopy can be a valuable tool for species discrimination, while simultaneously providing insight into chemical processes occurring within photosynthetic organisms. The spectral identity and separability of Hawaiian macroalgal taxonomic groups and invasive and native macroalgae are poorly known and thus were the focus of this study. A macroalgal spectroscopic library of 30 species and species complexes found in Hawaiʻi was created. Spectral reflectance signatures were aligned with known absorption bands of taxonomic division-specific photosynthetic pigments. Quadratic discriminant analysis was used to explore if taxonomic groups of algae and native versus invasive algae could be classified spectrally. Algae were correctly classified based on taxonomic divisions 96.5% of the time and by species 83.2% of the time. Invasive versus native algae were correctly classified at a rate of 93% and higher, although the number of invasive algal species tested was limited. Analyses suggest that there is promise for the spectral separability of algae investigated in this study by algal taxonomic divisions and native-invasive status. This study created a spectral library that lays the groundwork for testing the spectral mapping of algae using current airborne and forthcoming spaceborne imaging spectroscopy, which could have significant implications for coastal management.
... The studies within this cluster largely examine the potential benefits and detriments of seaweed to coral health, diversity, and ecosystem functionality [55][56][57]. b. Cluster 1: Solar Irradiation -Revolves around the impacts of sunlight on macroalgae physiology, specifically how differing light conditions affect photosynthesis, growth, and productivity [58][59][60]. ...
Seaweed research has gained substantial momentum in recent years, attracting the attention of researchers, academic institutions, industries, policymakers, and philanthropists to explore its potential applications and benefits. Despite the growing body of literature, there is a paucity of comprehensive scientometric analyses, highlighting the need for an in-depth investigation. In this study, we utilized CiteSpace to examine the global seaweed research landscape through the Web of Science Core Collection database, assessing publication trends, collaboration patterns, network structures, and co-citation analyses across 48,278 original works published since 1975. Our results demonstrate a diverse and active research community, with a multitude of authors and journals contributing to the advancement of seaweed science. Thematic co-citation cluster analysis identified three primary research areas: "Coral reef," "Solar radiation," and "Mycosporine-like amino acid," emphasizing the multidisciplinary nature of seaweed research. The increasing prominence of "Chemical composition" and "Antioxidant" keywords indicates a burgeoning interest in characterizing the nutritional value and health-promoting properties of seaweed. Timeline co-citation analysis unveils that recent research priorities have emerged around the themes of coral reefs, ocean acidification, and antioxidants, underlining the evolving focus and interdisciplinary approach of the field. Moreover, our analysis highlights the potential of seaweed as a functional food product, poised to contribute significantly to addressing global food security 2 and sustainability challenges. This study underscores the importance of bibliometric analysis in elucidating the global seaweed research landscape and emphasizes the need for sustained knowledge exchange and collaboration to drive the field forward. By revealing key findings and emerging trends, our research offers valuable insights for academics and stakeholders, fostering a more profound understanding of seaweed's potential and informing future research endeavors in this promising domain.
... Las estrategias que gestionan y mitigan los factores estresantes locales aumentan la capacidad de los corales para resistir las consecuencias de los factores estresantes globales. Por ejemplo, reducir la contaminación por sedimentos y nutrientes de las cuencas costeras es importante para garantizar agua clara y reducir el crecimiento excesivo de algas en los arrecifes de coral, particularmente después de daños causados por eventos de blanqueamiento o tormentas (Smith et al. 2010, Risk y Edinger 2011. ...
Resilience-based management strategies are gaining attention as tools to improve coral survival and recovery under increasingly stressful conditions. Prioritizing locations to implement these strategies depends on knowing where corals already show potential signs of resilience and how environmental conditions may shift with climate change. We synthesized environmental conditions and coral cover trends in Guam and American Samoa using present-day climate conditions and 2 future climate scenarios: Representative Concentration Pathways 4.5 and 8.5. We examined the spatial overlap between favorable and unfavorable environmental conditions and locations where coral reefs have maintained or increased coral cover over the past decade. Locations representing 4 combinations of the aforementioned characteristics may be subject to different management strategies: (1) conservation and restoration of robust corals, (2) restoration of declining corals, (3) conservation of genetic material of robust corals and stressor mitigation, and (4) no clear strategy for declining corals. We estimated areas in which multiple management actions could be performed based on these combinations. Under present-day climate conditions, the conservation of genetic material and stressor mitigation were overrepresented in Guam, comprising 23% of the study area; this declined to 15% in future climate scenarios. Coral restoration was at first underrepresented (0%). In American Samoa, the proportional area for each strategy remained consistent regardless of climate. Coral restoration was overrepresented, comprising 54% to 56% of the study area, whereas the conservation of genetic material and stressor mitigation were underrepresented (9% to 11%, respectively). Our approach offers a rapid way to assess where potential management actions could be applied based on data aggregated over large spatial extents, which can complement more detailed, labor-intensive assessments of reef community dynamics, particularly if distinct coral communities inform the boundaries of aggregation units. These results may guide managers in selecting ecologically suitable locations for implementing resilience-based management strategies for coral reefs.
... Recent studies reveal some degree of redundancy and complementary in feeding habits and ecological role among herbivorous fishes (Burkepile and Hay 2011;Adam et al. 2015b). Collectively, abundant and functionally diverse communities of herbivorous fishes can prevent overgrowth and succession of macroalgal communities delaying and potentially reversing phase shifts toward macroalgal-dominated stages (Burkepile and Hay 2010;Smith et al. 2010;Humphries et al. 2014). ...
Herbivory is an essential ecological process on coral reefs because it balances competition among benthic organisms such as corals and macroalgae. The geomorphological diversity of Cuban coral reefs and their distinctive protection levels present a unique opportunity to showcase the impacts of herbivory on reef dynamics. In this chapter we compiled information on the distribution and abundance of the essential reef herbivores (sea urchins and fishes) on the Cuban shelf and analyzed these data in light of reef characteristics and functioning (e.g., structure, benthic composition). We report an overall low (<1 Ind. m−2) presence of Diadema antillarum on the Cuban shelf and herbivorous fish biomass ranging from 11 g m−2 (La Habana) to 60 g m−2 (Jardines de la Reina), which may explain the overall high macroalgal abundance (47% cover). Our detailed review of Cuban reef literature reveals few studies addressing herbivory directly on coral reefs but many studies describing benthic and fish communities, which offer excellent potential for future studies. We describe two contrasting examples of herbivore effect on macroalgal communities and identify potential questions and research topics of interest for Cuba and the rest of the Greater Caribbean.
... Benthic primary productivity and the associated productivity of herbivorous fishes represents a core pillar of coral reef ecosystem functioning Brandl et al. 2019a). Indeed, herbivorous fishes are widely considered to be an integral component of coral reefs as their constant grazing pressure can maintain the biomass of algae through topdown control (Smith et al. 2010;Rasher et al. 2012;Fong et al. 2018). Moreover, in many parts of the world, the productivity of herbivorous fishes supports small-scale fisheries that provide human nutrition and livelihoods Edwards et al. 2014;Russ et al. 2015). ...
Herbivorous fishes, and the productivity of algal turfs, are widely viewed as central to the functioning of coral reefs. This understanding is largely based on clear-water reefs. Our knowledge of herbivorous fishes and the nature of their nutritional resources on turbid reefs, by contrast, remains relatively limited. We therefore explored the nature of herbivorous fishes and the epilithic algal matrix (EAM) on turbid coral reefs across the Dampier Archipelago in northern Western Australia. We conducted comprehensive surveys of herbivorous fish abundances across natural turbidity gradients. Moreover, we quantified the trophodynamic functioning of herbivorous fishes relative to EAM structure and productivity. We revealed a clear relationship between turbidity gradients and herbivorous fish abundance, with herbivorous fishes being virtually absent from high turbidity reefs. Across the Dampier Archipelago, EAMs were typified by sediment-laden turfs with a limited propensity to deliver nutritional resources to fishes, while the productivity (i.e. the capacity for individuals to grow and produce new biomass) of herbivorous fishes was low and a fraction of that documented on clear-water reefs in the Indo-Pacific. Given the tight coupling between herbivorous fishes and their nutritional resources, these findings imply bottom-up nutrient resource limitation, which is likely due to reduced light levels and sediment-laden conditions inhibiting EAM productivity on turbid reefs. Our results suggest that EAM-based trophic pathways may be particularly unproductive on turbid reefs, with this energetic pathway playing a limited role in reef functioning compared to reefs in clear water.
Graphical abstract
... However, humans are degrading these pillars of reef resilience. Land clearing for agriculture and urban development increases sediment, nutrients, and other pollutants in coastal runoff, thereby reducing light reaching the benthos, smothering corals, and facilitating algal growth and coral diseases (Fabricius 2005;Smith et al. 2010;Vega Thurber et al. 2014). Similarly, overfishing of herbivores to feed growing populations allows algae to proliferate and can drive transitions from coral-to algae-dominated reefs (Bellwood et al. 2004;Jackson et al. 2014). ...
Coral reefs are beginning to experience conditions unlike any in recent history. Understanding ecosystem function on future reefs will require reassessing ecological processes under novel environmental regimes. For many coastal reefs, severely degraded water quality will be a hallmark of these novel regimes. While herbivory has traditionally been considered essential for maintaining coral dominance, recent evidence from urban reefs suggests this pattern may be changing. Here, we reexamined the impacts of herbivores on a shallow, turbid reef exposed to extensive coastal development. We found that although herbivore biomass, size-structure, and grazing rates were significantly reduced relative to a nearby protected reef, coral cover on this shallow urban reef remained > 45%. In contrast, coral cover at the nearby protected site was roughly 50% lower. Differences in coral cover between the sites were due to greater cover of two groups of corals at the urban site: depth-generalist Orbicella spp., particularly O. faveolata, and Agaricia spp. with weedy life-history characteristics. Both groups are tolerant of low light but susceptible to coral bleaching. Our results suggest that diminished top-down pressure did not promote algal dominance. Instead, turbidity-induced reductions in available light drove community structure, leading to dominance of coral and algae species able to acclimate to low-light. Our study demonstrates how environmental context can alter the importance of critical processes on coral reefs and highlights the need to reexamine traditional paradigms in reef ecology to understand ecosystem function on future reefs.
... Benthic feeding fishes influence coral recruitment and survival through direct and indirect pathways. Herbivorous fishes can indirectly promote coral recruitment by consuming competitive macroalgae, which in turn, creates space for less palatable crustose coralline algae (CCA), which can increase coral recruitment and survival 10,15,17,[20][21][22] . However, both herbivores and corallivores can negatively affect coral recruitment through direct or accidental predation 23-26 . ...
... However, the role of microhabitats can depend on fish grazing; a previous experiment found coral recruitment was 9X higher in protected crevices in the uncaged than the caged treatments 23 . Yet nearly all studies have been limited at approximately 1 year in duration or less and have been conducted in regions that have historically or currently face high fishing pressure 16,17,21,24,36,37 . Therefore, it remains relatively unexplored how the role of fishes in structuring coral recruitment may vary through successional time, especially at a site with relatively intact consumer assemblages and intense grazing pressure. ...
... The algae, Lobophora, declined in abundance in these caged tiles over time 51 providing support for the hypothesis that coral-algae competition was stronger in year 1 than year 3. Furthermore, the community composition became www.nature.com/scientificreports/ more similar between the uncaged and caged tiles through time, with increases in Lobophora and declines in CCA on the uncaged tiles 51 suggesting competition and/or facilitation would likely show larger differences between caging treatments in year 1 than year 3. Exposure to fishes has been previously found to have both positive 10,17,21,22 and negative 16,23-25 impacts on coral recruitment. Caging can protect juvenile corals from predation and increase survival 12,52,53 , but excluding fishes can also increase the amount of macroalgae and decrease a coral facilitator, CCA 10,17,21,24 . ...
Ecosystems around the world are continuously undergoing recovery from anthropogenic disturbances like climate change, overexploitation, and habitat destruction. Coral reefs are a prime example of a threatened ecosystem and coral recruitment is a critical component of reef recovery from disturbances. Reef fishes structure this recruitment by directly consuming macroalgae and coral recruits or by indirectly altering the substrate to facilitate coral settlement (e.g., grazing scars). However, how these direct and indirect mechanisms vary through time remains largely unknown. Here, we quantified coral recruitment on settlement tiles with divots that mimic grazing scars and caging treatments to exclude or allow fish feeding over 3 years at Palmyra Atoll in the Pacific Ocean. We found that the positive and negative effects of fishes on coral recruitment varies through time. After 3 years, both grazing scars and fish grazing no longer predicted coral recruitment, suggesting that the role of fishes decreases over time. Our results emphasize that reef fish populations are important in promoting initial coral recovery after disturbances. However, over time, factors like the environment may become more important. Future work should continue to explore how the strength and direction of top-down control by consumers varies through time across multiple ecosystems.
... More recent work has lent support for a holistic view that avoids a strict top-down or bottom-up dichotomy and instead seeks to understand the relative strength of multiple, concurrent factors (Burkepile & Hay, 2006;Hunter & Price, 1992;McCary et al., 2021;McLaughlin & Zavaleta, 2013;Meserve et al., 2003). While there have been recent investigations into the simultaneous influences of top-down and bottom-up effects in various communities (Bruce, 2012;Gigliotti et al., 2020;Meserve et al., 2003;Michel et al., 2016;Sergio et al., 2007;Smith et al., 2010), relatively few studies have investigated these factors in carnivore communities (Gigliotti et al., 2020;Lonsinger et al., 2017;Schuette et al., 2013). Understanding the magnitude and direction of influence that top-down and bottom-up factors exert on carnivore populations is important given these species' diverse ecological roles (Ripple et al., 2014;Roemer et al., 2009). ...
Investigating species responses to trophic interactions and abiotic factors is crucial to better understanding their ecology and creating effective management strategies. In carnivore communities, smaller species are often regulated by larger ones via top‐down interference competition. Smaller subordinate carnivores can also be regulated by bottom‐up and abiotic factors, such as the availability of important prey, habitat features, and climatic conditions. However, substantial ambiguity remains regarding the relative roles these complex factors play in shaping subordinate carnivore populations, especially during winter. To investigate this issue, we conducted a large‐scale camera‐trapping study ( n = 197 sites distributed across a ~60,000 km ² landscape) using a balanced study design that sampled a gradient of forest disturbance and climatic conditions. We used dynamic occupancy modeling to examine the influences of top‐down (interference competition), bottom‐up (prey and habitat), and abiotic (climate) factors on a widespread, generalist subordinate carnivore, the red fox ( Vulpes vulpes ), in Maine, USA. Across three winters, we collected 107 red fox and 185 coyote ( Canis latrans ) daily detections, and 3875 snowshoe hare ( Lepus americanus ) detections. We found evidence for the top‐down effects of coyotes on red fox detection probability and site colonization. However, contrary to theoretical expectations, the association between coyotes and red foxes was positive rather than negative. Snowshoe hares had a positive association with local extinction by red foxes, which also contrasts with prevailing theory given that snowshoe hares are an important winter prey of red foxes in this ecosystem. The intensity of forest disturbance and the proportion of conifer forest had negative effects on red fox occurrence and detection probability, while snow depth had a strong negative effect on site colonization. Together, these results suggest red foxes are limited more by abiotic and bottom‐up factors related to habitat than by the top‐down interference competition or primary prey availability in winter. Our study supports recent findings that bottom‐up factors may shape carnivore distributions during less productive times of year. Our work also highlights how caution is needed when extrapolating previous results from summer studies to winter, as the role of top‐down and bottom‐up factors may change seasonally.
... Seafood is a globally traded commodity and one of the most highly internationally traded food items [5,19,53]. Globalisation has resulted in large transnational companies increasing consolidation and vertical integration across supply chains from production through to retail [19,46]. Yet for seafood products, supply chains generally consist of multiple nodes (i.e. a distinct organisation that is involved in producing and/or distribution [16]), with varying degrees of product processing and amalgamation prior to final sale [16,63]. ...
Seafood is a globally traded commodity, often involving complex supply chains which have varying degrees of
traceability. A robust traceability system for seafood supply chains enables the collection and communication of
key information about catch and fisheries origins vital for assurance of the legality and sustainability of seafood
products. End-to-end traceability is increasingly demanded by retailers, consumers, NGOs and regulatory bodies
to ensure food safety, deter IUU fishing and verify sustainable and ethical credentials. Here, we map three UK
seafood supply chains and evaluate traceability performance in: Dover sole landed in the south west of England,
North-East Atlantic (NEA) mackerel landed at Peterhead, Scotland, and brown crab and European lobster, landed
at Bridlington, England. Through a comparative analysis of traceability performance, this study suggests improvements
to the technologies, processes, and systems for traceability in the seafood sector. The application of
monitoring technologies and regulatory changes across the sector have increased traceability and potentially
reduced instances of IUU fishing. While shorter supply chains are more likely to achieve end-to-end traceability,
vulnerable nodes in processing and distribution networks may result in a loss of seafood traceability. While
traceability systems may provide sustainability information on seafood, a high level of traceability performance
does not necessarily equate to a sustainable source fishery. Encouragingly, while UK seafood supply chains are
meeting minimum regulatory requirements for traceability, in the present study, many stakeholders have indicated
ambitions towards traceability best practice in order to provide confidence and trust in the UK fishing
industry.
... Seafood is a globally traded commodity and one of the most highly internationally traded food items [5,19,53]. Globalisation has resulted in large transnational companies increasing consolidation and vertical integration across supply chains from production through to retail [19,46]. Yet for seafood products, supply chains generally consist of multiple nodes (i.e. a distinct organisation that is involved in producing and/or distribution [16]), with varying degrees of product processing and amalgamation prior to final sale [16,63]. ...
Seafood is a globally traded commodity, often involving complex supply chains which have varying degrees of traceability. A robust traceability system for seafood supply chains enables the collection and communication of key information about catch and fisheries origins vital for assurance of the legality and sustainability of seafood products. End-to-end traceability is increasingly demanded by retailers, consumers, NGOs and regulatory bodies to ensure food safety, deter IUU fishing and verify sustainable and ethical credentials. Here, we map three UK seafood supply chains and evaluate traceability performance in: Dover sole landed in the south west of England, NorthEast Atlantic (NEA) mackerel landed at Peterhead, Scotland, and brown crab and European lobster, landed at Bridlington, England. Through a comparative analysis of traceability performance, this study suggests improvements to the technologies, processes, and systems for traceability in the seafood sector. The application of monitoring technologies and regulatory changes across the sector have increased traceability and potentially reduced instances of IUU fishing. While shorter supply chains are more likely to achieve end-to-end traceability, vulnerable nodes in processing and distribution networks may result in a loss of seafood traceability. While traceability systems may provide sustainability information on seafood, a high level of traceability performance does not necessarily equate to a sustainable source fishery. Encouragingly, while UK seafood supply chains are meeting minimum regulatory requirements for traceability, in the present study, many stakeholders have indicated ambitions towards traceability best practice in order to provide confidence and trust in the UK fishing industry.
