Historical overfishing and the recent collapse of coastal ecosystems

Climate change and overfishing combine to drive the population decline of the Indo-Pacific humpback dolphins in the Pearl River Estuary from the Northern South China Sea

Overfishing and climate change pose significant threats to cetacean populations, yet the specific impacts on individual species, particularly cetaceans inhabiting complex coastal areas, are not well understood due to limited data. This study utilizes five years of field survey data, alongside fishery activity and climate change scenarios, to assess the population dynamics of the Indo-Pacific humpback dolphin in the Pearl River Estuary from the Northern South China Sea. Our results indicate a dramatic and ongoing decline in the humpback dolphin population over recent decades, decreasing from over 1000 to 742 individuals. The individual impact of climate change on biomass is moderate, showing changes between -1.3 % and + 11.97 %. Projected climate change scenarios reveal further population reductions, exacerbated by increasing fishing pressures, with declines ranging from 6.17 % to 20.39 %. Notably, our simulations highlight the detrimental effects of unrestrained socioeconomic development on humpback dolphins' viability and population. The dolphins exhibit adaptive dietary strategies to maintain energy levels in changing ecosystems; however, total energy intake still declines across all age classes, requiring increased foraging efforts. This may lead to decreased group sizes, altered distribution patterns, and reduced reproductive success, further increasing their vulnerability to additional stressors. The complex interplay between human activities and environmental changes in marine ecosystems, which significantly impacts cetaceans, provides crucial insights for developing integrated management strategies to safeguard the biodiversity and resilience of coastal marine ecosystems.

Heavy metal contamination in seawater, sediments, algae, and fish from Susah and Tobruk, Mediterranean Sea

Heavy metal contamination in marine environments poses serious threats to ecological health and human safety. This study examines the concentrations of zinc (Zn), copper (Cu), iron (Fe), cadmium (Cd), and lead (Pb) in sediments, seawater, and marine organisms (Ulva lactuca and Epinephelus marginatus) along the coastlines of Susah and Tobruk, Libya. The sampling involved 66 samples from 10 sites conducted in winter 2023. The contamination of cadmium clearly showed in all studied samples in Susah and Tobruk, whereas lead surpassed permissible in seawaters and livers, gills, and tissues of E. marginatus. The iron was high in the seawaters of Susah and Tobruk, particularly near Susah port and in Tobruk Gulf, reflecting the influence of industrial and anthropogenic activities. The results revealed that cadmium levels in the sediments indicated considerable contamination in Susah (CF = 5.897) and moderate contamination in Tobruk (CF = 1.12). The assessment employed several pollution indices, including the Geo-accumulation Index (Igeo), which indicated that all studied metals were uncontaminated in Tobruk, while Cd showed moderate contamination in Susah (Igeo = 1.975). The Nemerow Pollution Index (NI) categorized Susah as seriously polluted (NI = 6.01) and Tobruk as lightly polluted (NI = 1.195). Additionally, bioaccumulation factors for heavy metals in both U. lactuca and E. marginatus indicated acute contamination, particularly lead in fish tissues. These findings underscore the urgent need for effective environmental management strategies to address heavy metal pollution and protect the health of marine ecosystems and local communities reliant on these coastal resources. PRACTITIONER POINTS: Comprehensive pollution profiling (CF, Igeo, NI, and EF) in the study areas. GIS spatial mapping (heavy metal distribution and pollution sources identification) Bioaccumulation insights (bioaccumulation in fish and algae, showing ecological risk). Data for future monitoring (data for a significant gap in environmental monitoring) Public health awareness (urgent need for management and treatment options).

Exposure to plastic debris alters expression of biomineralization, immune, and stress-related genes in the eastern oyster (Crassostrea virginica)

The degradation of marine plastic debris poses a threat to organisms by fragmenting into micro- and nano-scale pieces and releasing a complex chemical leachate into the water. Numerous studies have investigated harms from plastic pollution such as microplastic ingestion and exposure to single chemicals. However, few studies have examined the holistic threat of plastic exposure and the synergistic impacts of chemical mixtures. The objective of this study was to measure changes in gene expression of gill and gonadal tissue of the eastern oyster (Crassostrea virginica) in response to plastic debris exposure during their first year, using RNA-seq to explore multiple types of physiological responses. Shell and polyethylene terephthalate plastic were used as substrate for the metamorphosis of larval oysters in a settlement tank. Substrate pieces were then transferred to metal cages and outplanted in pairs - shell cage and plastic cage - onto restoration reefs in the St. Mary's River, Maryland, USA. After 10 months of growth, the oysters were collected, gill and gonadal tissue removed, and sex identified. The tissues of six oysters from each sex and substrate type were then analyzed in RNA-seq. Both gill and gonadal tissue samples had altered expression of immune and stress-response genes in response to plastic exposure. Genes upregulated in response to plastic were enriched for gene ontology functions of proteolysis and fibrinolysis. Downregulated genes were involved in shell biomineralization and growth. One male oyster exposed to plastic had "feminized" gene expression patterns despite developing mature sperm, suggesting plastic leachate can alter gene expression and shift protandric individuals to develop as females. Plastic pollution may therefore reduce shell growth, initiate immune and stress responses, alter sex differentiation, and impact reproductive output of eastern oysters through changes in transcription.

A functional assessment of fish as bioturbators and their vulnerability to local extinction

The seabed is one of the key ecological interfaces on the planet, exerting a major influence on global biogeochemical cycles. Biological processes such as bioturbation - the reworking of sediment by activities of benthic fauna - are key in mediating fluxes of nutrients, carbon, and oxygen from the water column into the sediment. To date, most research on bioturbation has focused on the role of sediment-dwelling invertebrates with the contribution of other and often larger organisms such as fish largely overlooked. Here, we highlight the significant and underappreciated role of fish as bioturbators in benthic ecosystems and present the first systematic approach to assess fish bioturbation impact on the seabed based on ecological traits known to influence sediment reworking. We show that 185 fish species across 62 families are bioturbators on the UK continental shelf, exhibiting a range of bioturbation modes, for example through burrowing, feeding, and nesting activities. Our analysis demonstrates that many important bioturbators are highly vulnerable to loss and extinction. Out of the 185 fish species bioturbating on the UK shelf, 120 are commercially exploited, with some of the most significant bioturbators among the most highly commercially fished. Our findings highlight the risk of alteration of benthic ecosystem processes resulting from the potential removal of these key bioturbators. This novel framework provides a simple yet powerful tool for assessing fish contributions to benthic ecosystem functioning and represents a first step towards incorporating fish bioturbation into future seabed management decisions.

Challenges in expert ratings of marine habitat and species sensitivity to anthropogenic pressures

Expert knowledge can help fill gaps in quantitative empirical information about complex ecological phenomena. We examined the level of agreement between 21 studies that collected expert ratings of the sensitivity of species and habitats to human activities and their pressures as input data for mapping the human impact on marine ecosystems. Our analyses revealed broad agreement about which human activities and pressures many species and habitats are sensitive to. These agreements reflect a common view of the main threats to ocean ecosystems. In contrast, scores provided by individual experts varied both within and across studies. Sensitivity scores collected with the same method for different regions were often more similar than scores collected for the same region but with different methods. These results highlight how inconsistencies in the design of many expert surveys can lead to variable outcomes. It is important to employ more consistent and theoretically grounded methods and protocols when eliciting expert ratings of species' sensitivity to pressures, to ensure compatibility across studies and maintain rigour in analyses supporting effective ocean management.

Contrast in the density and biomass of fish in a reef system with different fishing intensity in the Mexican Caribbean

A wide range of fish species are caught in reef fisheries. However, fishing efforts tend to be highly selective in favor of large species, which generally have low population growth rates, making them more vulnerable to overfishing. When the decline of large predators occurs, fishing efforts start to focus on catching species from lower trophic levels, which can cause a trophic cascade effect. The objective of this research was to detect changes in the density and biomass of fish communities in areas with different fishing intensity in the study area. This study was carried out in the Banco Chinchorro Biosphere (BCBR) in the Mexican Caribbean and analyze the effect of fishing intensity on fish density and biomass, comparing data obtained from visual censuses with dependent information of the fishery. Evidence was found of a relationship between high fishing exploitation and low levels of density and biomass for Epinephelus striatus, E. guttatus and Lachnolaimus maximus. The decline of predators had no evident effect on the density and biomass of non-commercially important species. The density and biomass of commercially important fish species were influenced by the presence of algae, octocorals, hydrocorals and by variations in their catch per unit of effort (CPUE). This study detected that density and biomass have decreased in some species belonging to the Serranidae and Lutjanidae families in areas with high fishing intensity. On the other hand, little evidence was found that the density and total biomass of families of noncommercially important species increased through the decline of their predators. These results are consistent with previous work documenting how fishing activity affects fish species with high trophic levels. The information generated will help the Reserve's managers make decisions towards better management and conservation of fishery resources.

Ecological assessment of marine systems: How to conclude? Method and application to Western Mediterranean

The ecosystem approach is generally considered as the best way to manage human activities impacting the marine environment. Nevertheless, more than 20 years after the emergence of this new paradigm, whereas ecosystem-based management is theoretically implemented through an essentially systemic approach, in practice, it appears that the application of standards and criteria and the use of indicators lead to a predominance of analytical approaches and to reporting formats that are inappropriate for defining action programmes. This paper proposes a new methodological framework to produce, in a synthetic form, integrated ecosystem assessments that go beyond the juxtaposition of sectoral analyses. Its guiding principle is to use the general knowledge of the marine environment (understanding of system dynamics and interactions within the system through a systemic approach) to put into perspective the results obtained through criteria and methodological standards (understanding the state of ecological components and the pressures affecting them through analytical approaches). The new methodological framework includes the identification of appropriate typologies for activities and pressures, as well as for ecological components. An essential point is to group the ecological components within the following compartments: pelagic habitats and food webs; benthic habitats; areas at the land-sea interface; protected species; and commercial species. On each of these compartments, the application of a selection of descriptors is possible. The result is an optimization of analyses in comparison with the indiscriminate use of descriptors on each of the ecological components considered separately. A case study is presented on the French Western Mediterranean.

Spatial Change of Dominant Baltic Sea Demersal Fish Across Two Decades

The arange and biomass distribution of marine fish species offer insights into their underlying niches. Quantitative data are rare compared to occurrences and remain underused in species distribution models (SDMs) to explore realized niches-the actual space occupied by a species shaped by abiotic and biotic factors. Local densities drive differences in species contributions to ecological processes and ecosystem function rather than through presence alone. If a species growth rate is strongly controlled by macro-environmental conditions, then predicting geographical abundance or densities should be possible. We collated 20 years (2001-2020) of standardized scientific bottom trawl data to fit several versions of hierarchical generalized additive models using biomass (kg km-2) of four dominant demersal species (Common dab, European flounder, European plaice, Atlantic cod) within yearly and seasonal (winter and autumn) time windows. Covariates were represented with trawl-level geographic information (position, depth) and high-resolution oceanographic features. This work illustrates species-specific spatiotemporal biomass patterns across two decades and demonstrates superior predictive performance with seasonally variable smoothing terms, revealing seasonally different responses to oceanographic predictors. Firstly, we find relative stasis in Common dab biomass which is linked to the macro-environmental salinity gradient in the western Baltic Sea but with different temperature responses across seasons. Secondly, we show both European flounder and plaice have increased in biomass in the western Baltic Sea with different seasonal relationships to bottom temperature, and that flounder switches between salinity conditions based on season during spawning/feeding periods. Lastly, both juvenile and adult Atlantic cod life stages are shown to have declined most significantly in the Bornholm Deeps and the Gdańsk Deeps. For cod, we conclude that biomass was less reliably predicted in comparison to the other major Baltic demersals studied here, warranting dynamic fishing covariates as a formerly major commercial fishing target. These models approach more dynamic species distribution models and are increasingly valuable to constrain uncertainties in biogeographic forecasting which often rely on annually-averaged response curves, occurrence data, and suitability maps which rarely discriminate between areas of high and low biomass areas in space and time.

Active restoration of a long-lived octocoral drives rapid functional recovery in a temperate reef

Whether restoration actions achieve full ecological recovery is still debated. This is particularly controversial in the marine realm, where the success of restoration is mostly evaluated in terms of the short-term survival of transplanted organisms. In view of this, we combined population and trait-based approaches to explore the long-term effectiveness of active restoration of a key Mediterranean octocoral. For this purpose, an assemblage with restored Corallium rubrum colonies was monitored over 10 years and compared with a nearby reference site. Our results revealed growth of the transplanted colonies followed by a change in the functional structure (i.e., dominance and diversity of traits) of the restored assemblage. This change was related not only to the development of the coral but also to the arrival and/or increase of species with different traits. Overall, our findings provide an example of how active restoration of long-lived octocorals can be an effective tool for recovering high-diverse coralligenous assemblages at decadal timescales.

Deploying artificial nurseries in port areas: A complementary strategy to fisheries management for supporting coastal fish populations

Conservation measures are essential for supporting biodiversity in areas impacted by human activities. Over the last decade, efforts to rehabilitate fish nursery habitats in ports through eco-engineering have gained attention. While these interventions show promise at a local level such as increased juvenile fish densities on artificial eco-engineered habitats compared to unmodified port environments there has been no comprehensive assessment of their contribution to coastal fish population recovery or their effectiveness relative to traditional conservation measures like fishing regulations. In this study, we employed the ISIS-Fish model, which integrates fish population dynamics with fisheries management, to examine the commercial coastal fish species, white seabream (Diplodus sargus), in the highly artificialized Bay of Toulon. By simulating different rehabilitation scenarios and fisheries management strategies, we provided the first quantitative evaluation of eco-engineered structure deployment in ports, covering 10% and 100% of the available port's linear extent. We compared these rehabilitation outcomes against the effects of enforcing strict minimum catch sizes. Our findings indicate that while port nursery habitat rehabilitation can contribute to fish population renewal and increase catches, the benefits remain limited when project scales are small, especially when compared to the impacts of strict fishing regulations. However, a synergistic effect was observed when combining nursery rehabilitation with fishing control measures, leading to significant improvements in fish populations and catch yields. This study offers the first quantitative analysis of nursery habitat rehabilitation in ports, highlighting its potential as a supplementary strategy to fisheries management, though less effective on its own than robust regulatory measures.

Seasonal effects of extreme climate events and sea surface temperature indicators on the vulnerability of marine pelagic fisheries in the Bay of Bengal region

The study highlights the vulnerability of the eastern coast to tropical cyclones and the unique characteristics of the Bay of Bengal region. Seasonality, driven by global climatic events and geography, significantly affects the marine ecosystem. Furthermore, it underscores the effects of extreme climate events on marine pelagic fisheries and advocates for a state-based approach to raise awareness among government institutions and fishing communities. Findings reveal a significant negative relationship between Sea Surface Temperature (SST) and fish-catch (coefficient = -0.09, p < 0.01), indicating that rising SST adversely affects pelagic fish populations. Moreover, increased frequency of extreme events (-0.12 to -2.06, p < 0.05 to p < 0.01) and disturbances (-0.149 to -0.679, p < 0.05) exhibits detrimental impacts across various models. Notably, seasonal variations play a crucial role, with quarters 1, 3, and 4 demonstrating positive associations (0.186-0.604, p < 0.1 to p < 0.05) with fish-catch, signifying potentially favourable conditions during specific seasons. State-specific analysis highlights diverse impacts, wherein West Bengal experiences substantial negative effects from extreme events (-2.056, p < 0.01), emphasizing regional disparities. These findings underscore the need for regionalized mitigation strategies and sustainable fishing practices to ensure the future of the Bay of Bengal's marine ecosystem.

Exploring technical improvements for environmental nucleic acids-based biodiversity assessment and management in coastal ecosystems

Assessing and conserving marine biodiversity remain critical global challenges, particularly in highly disturbed coastal regions. The use of environmental DNA (eDNA)-metabarcoding has revolutionized biodiversity assessment and management; however, the prevalence of both false positives and negatives continues to be a significant concern. To address these technical errors, we tested two potential methodological improvements in the highly disturbed Guangdong-Hong Kong-Macao Greater Bay Area: (1) the use of random whole-genome amplification (WGA) to reduce false negatives derived from low eDNA concentration, and (2) the application of environmental RNA (eRNA)-metabarcoding to mitigate false positives arising from eDNA contamination by human activities. Using fish communities as our target, we found that WGA enhanced downstream PCR amplification for metabarcoding but significantly reduced the detection of rare taxa, altered community structure, and increased false negatives (p < 0.001 for all tests). Interestingly, WGA led to higher levels of false negatives in more biodiverse communities. eDNA-metabarcoding revealed that 20.9%-23.6% of detected taxa were pure freshwater species (false positives) incapable of surviving in estuarine and coastal regions, highlighting the often-overlooked eDNA contamination in disturbed coastal ecosystems. In contrast, eRNA-metabarcoding significantly reduced false positives (p < 0.001), with error taxa accounting for only 2.5%-6.3% of all detections. Comparisons between eDNA and eRNA metabarcoding further revealed differences in their rare taxa recovery capacity. The findings provide critical insights into method selection for biodiversity assessment and management in highly disturbed coastal regions and highlight the need for further technical improvement of eDNA and eRNA-based biodiversity monitoring and conservation in aquatic ecosystems.

Post-Fishing Ban Period: The Fish Diversity and Community Structure in the Poyang Lake Basin, Jiangxi Province, China

Between 2022 and 2023, four systematic fish surveys were carried out in the Poyang Lake basin (PLB), capturing 49,192 fish (7017 kg) and identifying 120 species from 10 orders, 21 families, and 70 genera. Cypriniformes were the most dominant, accounting for 79 species. The spring and autumn surveys collected 25,734 and 23,458 individuals, respectively, with corresponding biomasses of 3978 kg and 3038 kg. Dominant species (IRI > 1000) in the study area included Hemiculter leucisculus, Megalobrama skolkovii, Hypophthalmichthys molitrix, and Aristichthys nobilis. Additionally, critically endangered species such as Ochetobius elongatus, Myxocyprinus asiaticus, and Acipenser sinensis as well as exotic species like Cirrhinus mrigala and euryhaline species like Cynoglossus gracilis and Hyporhamphus intermedius were observed. Hierarchical clustering grouped the survey stations into three distinct areas (PYS, XBMS, and XBUS), with the ANOSIM analysis showing highly significant differences (R = 0.893, p < 0.01). Redundancy analysis (RDA) indicated that in spring, total phosphorus (TP) and temperature were the main factors influencing variability (80.50%), while in autumn, temperature, oil, and pH were the key factors (75.20%). This study emphasizes the predictable changes in fish community composition caused by environmental gradients and highlights the need for ongoing monitoring to effectively manage and protect the ecosystem, particularly in the post-fishing ban period.

Oyster reef recovery: Impacts of rotational management and restoration efforts on public fishing grounds

Coastal ecosystems are degraded worldwide and oyster reefs are among the most threatened coastal habitats. Oysters are a critical ecosystem engineer and valuable fishery species, thus effective management strategies must balance tradeoffs between protecting reef ecosystems and continued human use. Management practices for oysters commonly incorporate shell replenishment (provisioning hard substrates to increase reef relief) and spatial management (rotational harvest areas or sanctuaries); however, the impact of these practices on reef dynamics and fisheries outcomes are poorly understood, particularly on harvested reefs. This project examines the efficacy of shell replenishment and spatial management practices on public fishing grounds by analyzing long term datasets available for the Rappahannock River in the Chesapeake Bay, USA. Using generalized linear mixed effects models, we examine how oyster reef metrics (brown shell substrate L m-2, recruit density m-2, market density m-2) and fisheries efficiency (meeting daily bushel harvest limit or not) respond to management actions. Our results indicate that a 3 y rotation maintains the underlying reef structure, enhances recruitment, and increases market sized oyster density by 1.23 oysters m-2 on average. Sanctuaries and harvested reefs had comparable brown shell and recruit density; however, sanctuaries had higher market oyster density on average. Shell replenishment practices directly enhanced harvester efficiency, particularly in harvest areas with poor reef condition. Our results indicate that low levels of replenishment (∼1000 bushels acre-1) provide substantial benefits to oyster reefs and the fishery. This study is the first to evaluate the marginal benefits of replenishment activities for biological and fisheries outcomes, and a novel, real world assessment for oyster restoration practices on public fishing grounds. Cumulatively, our findings show that spatial management and replenishment practices enhance oyster reefs in temperate estuaries and offers a framework applicable to other degraded ecosystems worldwide.

Effects of protection on large-bodied reef fishes in the western Indian Ocean

Predatory and large-bodied coral reef fishes have fundamental roles in the functioning and biodiversity of coral reef ecosystems, but their populations are declining, largely due to overexploitation in fisheries. These fishes include sharks, groupers, Humphead wrasse (Cheilinus undulatus), and Green Humphead parrotfish (Bolbometopon muricatum). In the western Indian Ocean, this situation is exacerbated by limited population data on these fishes, including from conventional visual census methods, which limit the surface area surveyed. We developed a rapid timed scuba swim survey approach for application over large areas for estimation of the abundance of large-bodied reef fishes and assessment of the effectiveness of marine protected areas (MPAs) in maintaining these species' populations. Using this method, we sampled 7 regions in the western central Indian Ocean and Gulf of Aden, including 2 remote reference locations where fishing is prohibited. Eight families were selected for the surveys from across 3 categories: pelagic, demersal, and large-bodied single species. Sharks (Carcharhinidae) were absent in 5 of the 7 regions, observed only in Mozambique and the Chagos Archipelago. Tunas (Scombridae) and barracudas (Sphyraenidae) were rarely observed (none in Madagascar, Djibouti, and Iles Glorieuses). The Giant grouper (Epinephelus lanceolatus) was absent in all regions, Humphead wrasse was absent in Comoros and Iles Glorieuses, and Green Humphead parrotfish was observed at only one site in Tanzania. The MPAs were not effective in protecting these single large-bodied species or the 4 pelagic families, except for sharks in the highly protected reference locations. However, MPAs with medium levels of protection were effective in maintaining the abundance of some demersal families, notably large-bodied groupers. Our results support the hypothesis of local extirpation of these large-bodied fishes on many coral reefs in the western Indian Ocean.

Ecological interactions amplify cumulative effects in marine ecosystems

Biodiversity encompasses not only species diversity but also the complex interactions that drive ecological dynamics and ecosystem functioning. Still, these critical interactions remain overwhelmingly overlooked in environmental management. In this study, we introduce an ecosystem-based approach that assesses the cumulative effects of climate change and human activities on species in the St. Lawrence marine ecosystem, eastern Canada, by explicitly accounting for the effects arising from species interactions within a multiple stressors framework. Our findings reveal previously unrecognized threats to exploited and endangered fishes and marine mammals, exposing noteworthy gaps in existing management and recovery strategies. By integrating the less obvious yet no less substantial effects arising from species interactions into cumulative effects assessments, our approach provides a robust tool to guide more comprehensive and effective management and conservation efforts for marine species.

Downscaling global reference points to assess the sustainability of local fisheries

Multispecies coral reef fisheries are typically managed by local communities who often lack research and monitoring capacity, which prevents estimation of well-defined sustainable reference points to perform locally relevant fishery assessments. Recent research modeling coral reef fisheries globally has estimated multispecies sustainable reference points (i.e., the maximum reef fish yields that can be harvested sustainably and the corresponding reef fish standing biomass at which those are expected to be achieved) based on environmental indicators. These global reference points are a promising tool for assessing data-poor reef fisheries but need to be downscaled to be relevant to resource practitioners. Using a small-scale multispecies reef fishery in Papua New Guinea, we estimated sustainable reference points and assessed the sustainability of the fishery by integrating global-scale analyses with local-scale environmental conditions (i.e., coral cover, sea surface temperature, ocean productivity, and whether the reef is an atoll), reef area, fish catch and standing biomass estimates, and fishers' perceptions. Local-scale relevant data were obtained from a combination of remote sensing products, underwater visual censuses, catch surveys, and household structured social surveys. Our sustainability assessment based on downscaled estimated sustainable reference points was consistent with local fishers' perceptions. Specifically, our downscaled results suggested that the fishing community was overfishing their reef fish stocks and stocks were below biomass levels that maximize production, making the overall reef fishery unsustainable. These results were consistent with fisher perceptions that reef fish stocks were declining in abundance and mean fish length and that fishers had to spend more time finding fish. Our downscaled site-level assessment revealed severe local resource exploitation, the dynamics of which were masked in national-scale assessments, emphasizing the importance of matching assessments to the scale of management. Overall, we show how global reference points can be applied locally when long-term data are not available, providing baseline assessments for sustainably managing previously unassessed multispecies reef fisheries around the globe.

Evaluating historical changes in a mussel bed community in northern California

Marine foundation species are increasingly impacted by anthropogenic stressors, driving a loss of diversity within these critical habitats. Prior studies suggest that species diversity within mussel beds has declined precipitously in southern California, USA, but it is unclear whether a similar loss has occurred farther north. Here, we resurvey a mussel bed community in northern California first sampled in 1941 to evaluate changes in diversity after 78 years. More broadly, we explore the value and potential challenges of using imperfect historical data to assess community changes. Our 2019 survey documented 90 species/taxa across 10 phyla. The majority of species (~ 72%) were common to all replicate plots, suggesting that variation in species diversity over small spatial scales was unlikely to mask temporal changes. In contrast to results from southern California, we observed no decline in species diversity between timepoints. However, there were shifts in species composition, with an increase in the abundance of southern species and a decrease in northern species, consistent with warming observed at a nearby shoreline site. Overall, our findings are an encouraging sign for the health of this mussel bed community in northern California and illustrate how non-traditional data can contribute to assessments of long-term ecological change.

Loss of Earth's old, wise, and large animals

Earth's old animals are in decline. Despite this, emerging research is revealing the vital contributions of older individuals to cultural transmission, population dynamics, and ecosystem processes and services. Often the largest and most experienced, old individuals are most valued by humans and make important contributions to reproduction, information acquisition and cultural transmission, trophic dynamics, and resistance and resilience to natural and anthropogenic disturbance. These observations contrast with the senescence-focused paradigm of old age that has dominated the literature for more than a century yet are consistent with findings from behavioral ecology and life history theory. In this work, we review why the global loss of old individuals can be particularly detrimental to long-lived animals with indeterminate growth; those with increasing reproductive output with age; and those dependent on migration, sociality, and cultural transmission for survival. Longevity conservation is needed to protect the important ecological roles and ecosystem services provided by old animals.

Insights Gained from Including People in Our Models of Nature and Modes of Science

Across the natural sciences, humans are typically conceptualized as external disruptors of nature rather than adaptable components of it. Historical evidence, however, challenges this dominant schema. Here, we describe the broad repertoire of ecological functions performed by people in place-based societies across the Pacific Ocean over millennia, illustrating their roles as ecosystem engineers, dispersers, bioturbators, nutrient cyclers, predators, and herbivores. By considering the reciprocal relationships between people and the ecosystems within which they are embedded, evidence of humanity's ability to experiment, learn, adapt, innovate, and sustain diverse and resilient social-ecological relationships emerges. Therefore, recognizing people as inseparable components of marine ecosystems and their millennia of engagement with coastal ocean spaces is critical to both understanding marine ecosystems and devising resilient and equitable ocean policies.

Overcoming Shifting Baselines: Paleo-Behaviour Reveals Industrial Revolution as Tipping Point

Human activities have significantly altered coastal ecosystems worldwide. The phenomenon of shifting baselines syndrome (SBS) complicates our understanding of these changes, masking the true scale of human impacts. This study investigates the long-term ecological effects of anthropogenic activities on New Zealand's coastal ecosystems over 800 years using fish otolith microchemical profiling and dynamic time warping across an entire stock unit. Results reveal a shift in snapper (Chrysophrys auratus; Sparidae) habitat-use behaviour, transitioning from low-salinity estuarine environments to higher-salinity habitats, correlating with ongoing land-use changes. This shift coincided with New Zealand's localised Industrial Revolution, which served as a tipping point for widespread ecosystem transformation. By comparing current coastal fish movement profiles with historical baselines, we provide evidence to address SBS and guide conservation strategies. Re-establishing pre-industrial habitat-use behaviours in snapper will indicate successful habitat restoration, promoting overall ecosystem connectivity and resilience. Our findings enable more effective habitat restoration measures and sustainable management practices, informing policies for maintaining coastal biodiversity and ecosystem function.

Transient cognitive impacts of oxygen deprivation caused by catch-and-release angling

Vertebrate brain function is particularly sensitive to the effects of hypoxia, with even brief periods of oxygen deprivation causing significant brain damage and impaired cognitive abilities. This study is the first to investigate the cognitive consequences of hypoxia in fish, specifically induced by exhaustive exercise and air exposure, conditions commonly encountered during catch-and-release (C&R) practices in recreational fishing. Angling exerts substantial pressure on inland fish populations, underscoring the need for sustainable practices like C&R. While C&R survival rates are generally high, understanding its sublethal impacts is crucial for evaluating the practice's ethical and ecological sustainability. We examined the effects of these stressors on the cognitive function of 238 rainbow trout, using the free movement pattern Y-maze method to assess working memory through navigational search patterns during free exploration sessions. Our results showed that air exposure led to short-term (3-4 h post-treatment), but transient impairments in working memory, with no long-term cognitive deficits observed at one week and one month post-treatment. These findings emphasize the high tolerance of fish to hypoxia and support the sustainability of C&R as a tool in fisheries management.

Oyster Restoration to Recover Ecosystem Services

Oyster reef loss represents one of the most dramatic declines of a foundation species worldwide. Oysters provide valuable ecosystem services (ES), including habitat provisioning, water filtration, and shoreline protection. Since the 1990s, a global community of science and practice has organized around oyster restoration with the goal of restoring these valuable services. We highlight ES-based approaches throughout the restoration process, consider applications of emerging technologies, and review knowledge gaps about the life histories and ES provisioning of underrepresented species. Climate change will increasingly affect oyster populations, and we assess how restoration practices can adapt to these changes. Considering ES throughout the restoration process supports adaptive management. For a rapidly growing restoration practice, we highlight the importance of early community engagement, long-term monitoring, and adapting actions to local conditions to achieve desired outcomes.

Assessing how restoration can facilitate 30×30 goals for climate-resilient coastal ecosystems in the United States

Ecosystems globally have reached critical tipping points because of climate change, urbanization, unsustainable resource consumption, and pollution. In response, international agreements have set targets for conserving 30% of global ecosystems and restoring 30% of degraded lands and waters by 2030 (30×30). In 2021, the United States set a target to jointly conserve and restore 30% of US lands and waters by 2030, with a specific goal to restore coastal ecosystems, namely wetlands, seagrasses, coral and oyster reefs, and mangrove and kelp forests, to increase resilience to climate change. Although US efforts to conserve and restore coastal ecosystems have increased in recent decades, critical knowledge gaps about the effectiveness of past and current efforts remain. To address key knowledge gaps, we first collated information on current and historic extent and drivers of change for wetlands, seagrasses, coral and oyster reefs, and mangrove and kelp forests in the United States. We then synthesized guiding principles from the literature for restoration practitioners to evaluate ecosystem trade-offs, sustain and enhance ecosystem connectivity, bolster climate resilience, and promote social equity. Significant investment in standardized ecosystem mapping and monitoring and multispecies, landscape-scale restoration efforts can improve resilience of coastal ecosystems to climate change and help the United States achieve its 30×30 target.

Diversity and future perspectives of Mediterranean deep-water oyster reefs

Anthropogenic and climate factors are increasingly affecting the composition and functions of many marine biogenic reefs globally, leading to a decline in associated biodiversity and ecosystem services. Once dominant ecological component, modern oyster reefs in the Mediterranean and Black Sea and the Atlantic Ocean have already been profoundly altered by overharvesting, habitat loss and the introduction of alien species. Far less known are deep-water oyster reefs, which can however form substantial biogenic structures below 30 m depth. Here we analyze the diversity of benthic assemblages associated with deep-water oyster reefs formed by the gryphaeid Neopycnodonte cochlear, and other mesophotic habitats in the central Mediterranean Sea using a taxonomic and functional approach. Our findings suggest that deep-water oyster reefs may act as hotspots of biodiversity and ecological functions in the Mediterranean Sea under current conditions, having also an edge in survival in a changing ocean.

Abalones at risk: A global Red List assessment of Haliotis in a changing climate

There is increasing awareness that marine invertebrates such as abalones are at risk from the combined stressors of fishing and climate change. Abalones are an important marine fishery resource and of cultural importance to Indigenous and non-Indigenous people. A highly priced marine delicacy, they are inherently vulnerable: individuals are slow-growing and long-lived and successful reproduction requires dense assemblages. However, their global conservation status is poorly understood. Using IUCN Red List methodology, we assessed the extinction risk to all 54 species of abalone (genus Haliotis). Of the 21 fished commercially for human consumption either now and/or in the past, 15 (71.43%) are classified as threatened, i.e., those identified as Critically Endangered, Endangered or Vulnerable. Of the 33 unexploited species, only five (15.15%) are so classified, making exploited species over four times more likely to face extinction, underscoring the impact of fishing on abalones already confronting a changing climate. The highest concentration of threatened species occurs along the North American Pacific coast. Here six of the seven species have been exploited, yet despite years of fishery closures with exemptions only in Alaska and Mexico, all are categorised as threatened. Climate driven stressors have led to mass mortalities, with competition from sea urchins and disease, aggravated by harmful algal blooms. In Australia the picture is mixed despite robust stock management, with some regions experiencing mass mortalities from marine heatwaves and viral spread. Poaching has reached its apogee in South Africa, where organised criminal gangs have reduced the legal fishery of Haliotis midae, 'perlemoen' almost to a footnote, accompanied by widespread recruitment failure. In response, the authorities have focused on abalone ranching and stock enhancement. In Japan, with a long history of abalone fishing, wild stocks are routinely supplemented with hatchery-bred juveniles. Collaboration between restoration aquaculture and fisheries, including sea urchin control and kelp restoration, offers hope for rebuilding stocks against a backdrop of escalating environmental stressors.

Steep Decline in the Rare Flat Abalone, Haliotis walallensis, Following Fishing Exploitation and a Marine Heat Wave: The Next Neoextinction?

Ocean warming is impacting marine systems directly and indirectly via intensifying multiple stressors such as hypoxia, acidification, and kelp forest collapse potentially exacerbating neoextinctions. Abalones are extremely vulnerable to both ocean warming and fishing stressors making them marine "canaries in the coal mine". The rare flat abalone, Haliotis walallensis, has been subject to a targeted commercial fishery and then exposed to an extreme marine heat wave. We examine the current status of flat abalone before and after a marine heat wave of 2014-2016 and the concomitant collapse of the bull kelp (Nereocystis leutkeana) forest in 2015. We find that flat abalone density (as assessed in surveys) and abundances (inside deployed "abalone modules") in the core of the range dropped to near-zero after the marine heat wave and have not recovered. Further, we examine the status of flat abalone in southern Oregon after both overfishing and the kelp forest collapse and find dramatic declines, especially in former fishery hot spots. Our results show that flat abalone have experienced a major decline and may be an example of a neoextinction in the making. A standardized and well-funded status review and proactive restoration plan, if not too late, are both critically needed for flat abalone throughout its range.

Trophic organization of the benthic communities off the South Italian coasts: A review with a modelistic approach

Limited data are available about the coastal ecology of the Calabria region, in the southern Italy. As well, data about the levels of biodiversity and the structure of food webs in these environments are totally missing. However, considering the wide range of physical and ecological conditions distinguishing these ecosystems, a remarkable spread of biodiversity is expected. This review represents a first attempt to describe and estimate the structure of the food webs in a range of shallow stations along the south-western coasts of southern Italy, in the Ionian Sea. They comprise a Special Area of Conservation (Amendolara shoal), an urbanized area (Sibari), a sandy area impacted by industrial installations (Corigliano) and a seagrass meadow (Calopezzati). For each of these stations, we produced ecological simulation models based on the available information in order to estimate the structure of food webs. In particular, the patterns of distribution of trophic resources resulting from literature data were statistically compared to a theoretical model based on the physical and ecological features of coastal ecosystems. The model was responsive and predicted remarkable differences in the compartmentalization of trophic resources among stations, due to the diversity of substrates and the anthropic activities impacting each area. Large availability of resources for omnivores and detritivores characterized most stations. A noteworthy richness of trophic resources for herbivores was forecasted off Amendolara and Calopezzati. In parallel, the model obtained for the urbanized area of Sibari predicted a higher abundance of trophic resources for filter feeders, especially in the deepest station.

Physiological response of longfin smelt to changing temperatures and turbidities

Coastal estuaries globally, including the San Francisco Estuary (SFE), are experiencing significant degradation, often resulting in fisheries collapses. The SFE has undergone profound modifications due to population growth, industrialization, urbanization and increasing water exports for human use. These changes have significantly altered the aquatic ecosystem, favouring invasive species and becoming less hospitable to native species such as the longfin smelt (Spirinchus thaleichthys). With longfin smelt abundance declining to <1% of historical numbers, there is a pressing need for laboratory-based experiments aimed at investigating the effects of varying environmental conditions on their stress response and physiology. This study explored the impact of temperature (11 and 14°C) and turbidity maintained with algae (1, 4 and 11 nephelometric turbidity units (NTU)) on the physiological condition of juvenile longfin smelt. Fish were sampled after 2 and 4 weeks in experimental conditions and analysed for whole-body cortisol, glucose, lactate and protein. Condition factor was calculated using length and weight measurements. Critical thermal maximum trials were conducted to assess how prior rearing conditions affected upper thermal tolerance. Cortisol levels were significantly higher in fish held in low-turbidity conditions, whilst glucose levels were significantly greater at lower temperatures and higher turbidities. Protein-to-mass ratios were significantly greater in higher turbidity conditions, with a significant interaction between temperature and turbidity further influencing these ratios. Moreover, 14°C led to diminished condition factors but increased upper thermal tolerances (26.3 ± 0.05 vs 24.6 ± 0.18) compared to longfin smelt at 11°C, highlighting a potential trade-off between the induction of defense mechanisms and subsequent reductions in energy and growth. Data suggest that cooler temperatures (11°C) and elevated turbidities (11 NTU) can benefit juvenile longfin smelt by reducing stress and enhancing growth and energy. These findings hold significant implications for informing and optimizing future endeavours in the culturing and conservation of this species.

Contrasting pollution responses of native and non-native fish communities in anthropogenically disturbed estuaries unveiled by eDNA metabarcoding

Understanding the influence of environmental pollutants on the assembly mechanisms of estuarine fish communities is vital for addressing conservation challenges in these biodiverse ecosystems. Although significant research has explored the toxic impacts of pollutants such as petroleum, heavy metals, and eutrophication on individual species and populations, their effects on community assembly processes and the differential responses of native versus non-native fish at the meta-community level remain inadequately understood. This study utilized environmental DNA (eDNA) metabarcoding to analyze fish community diversity across 28 subtropical estuaries in China, assessing how these pollutants affect community composition and assembly mechanisms. Results indicated that eDNA was 2.54 times more effective than traditional methods in species identification, while also enabling the detection of a higher number of non-native fish species and more diverse functional guilds within estuarine ecosystems. A significant distance decay pattern (p < 0.05) was observed among native fish, whereas non-native species exhibited non-significant patterns. Neutral and null models showed that non-native species had significantly higher migration rates (0.005939 vs 0.001757) and a greater contribution of stochastic processes (82.38 % vs 70.59 %) compared to native species. Additionally, distance-based redundancy analysis (db-RDA), variance partitioning analysis (VPA), and correlation analyses revealed that native species were strongly constrained by environmental factors, particularly oil, Hg, Zn, Pb, Cr6+, and NH4+, while non-native species displayed notable resilience to these pollutants. These findings highlight the potential for non-native species to disproportionately influence community dynamics and assembly through unrestricted random dispersal amid environmental disturbances. This research clarifies the contrasting ecological responses of native and non-native fish communities to anthropogenic pressures in estuarine environments, offering essential insights into ecosystem resilience and informing biodiversity conservation strategies in rapidly changing coastal ecosystems.

Diet, feeding, and niche overlap of west coast steenbras (Lithognathus aureti) and silver kob (Argyrosomus inodorus) in the northern Benguela

In this study, we described and compared the diet, monthly feeding intensity, and condition of west coast steenbras (Lithognathus aureti) and silver kob (Argyrosomus inodorus) caught at a unique habitat in the northern Benguela. Stomach contents of 179 west coast steenbras and 114 silver kob caught from October 2020 to September 2022 were investigated. The peak in feeding intensity of west coast steenbras appeared to be opportunistic during winter and summer periods depending on food availability. The fish condition, however, peaked at the beginning (October) and at the end (April) of the austral summer spawning period, with the hepatosomatic index (HSI) at 1.5% and the condition factor (CF) at 0.022%. Seven prey taxa were found in the diet of west coast steenbras (bivalves, bony fishes, other mollusks, algae, crustaceans, cnidaria, and polychaetas) and six taxa in the diet of silver kob (bivalves, crustaceans, bony fishes, algae, starfish, and zooplankton), indicating generalist feeding behavior in both the species. The bivalves were the most important prey items in the diet of west coast steenbras (95.9% index of relative importance [IRI]). The most important prey items in the diet of silver kob were crustaceans (83.1% IRI) and bony fishes (16.0% IRI). Crustaceans were most important in the diet of small-to-medium-sized silver kob, whereas bony fishes were most important in the diet of larger silver kob (>75 cm), with significant differences of IRI% by size class. Schoener's index of niche overlap indicated a relatively low overall niche overlap (0.11) between west coast steenbras and silver kob. This allows them to coexist as their feeding habits allow them to occupy unique niches in the coastal reef and sandy habitat and reduce competition for resources.

Investigating the determinants of marine environmental degradation in Africa: What roles can economy, population, capture and energy play?

This study firstly examines the quality of marine eco-environment in Africa using Tapio decoupling model, and analyzes the sustainability level of the development of "population agglomeration - marine environment - economic growth". Secondly, a series of econometric tools, such as ARDL, FMOLS, AMG model and DH panel causality test, are used to investigate the long- and short-term impacts of economic growth, population agglomeration, marine capture and energy consumption on the African marine eco-environment, and to analyze the differences between the sub-regions in Africa. The results indicate that: Adebayo and Kirikkaleli (2021) (Adebayo and Kirikkaleli, 2021) the decoupling state of "population-environment" has shifted from expansive negative decoupling to more optimized strong decoupling, and "economy-environment" has gradually changed from strong negative decoupling and expansive negative decoupling to strong decoupling. Ali et al. (2017) (Ali et al., 2017) There existed a bi-directional causal relationship between the degree of marine environment degradation and economic growth, population agglomeration, marine capture and energy consumption. Al-Mulali and Sab (2012) (Al-Mulali and Sab, 2012) In the short term, the economic EKC hypothesis does not hold in North and West Africa, while Central, East and Southern Africa are consistent with the EKC hypothesis. In the long term, the EKC hypothesis is valid in Central, East and Southern Africa, while is not valid in North and West Africa. Overall, reducing population agglomeration levels, marine fishing and energy consumption might mitigate marine environmental degradation in Africa.

eDNA technology reveals fish species diversity and ecological corridor function in large raft mussel aquaculture area in the East China Sea

Human activities have transformed coastal environments by introducing numerous artificial structures that impact local ecosystems. Our study investigated fish species diversity in the mussel farm (MF) and the surrounding natural reef habitat (NH) around Gouqi Island in the East China Sea (ECS). Gouqi Island, which hosts the largest mussel farm in ESC, is also a critical region for marine fish activity. We monitored fish species diversity across four seasons for the first time using eDNA technology in December (winter) 2022, March (spring), June (summer), and September (autumn) 2023. We recorded a total of 55 fish species across 49 genera, 33 families, and 10 orders. Alpha diversity analysis revealed that species diversity peaked in summer throughout the year. Diversity in the mussel farming area was significantly higher than in the natural reef habitat. Principal Component Analysis (PCA) and Analysis of Similarities (ANOSIM) confirmed significant differences in community composition between the two habitats (p < 0.01), with a more stable community structure in the mussel farm. This indicates that the mussel farming area supports a distinct fish community compared to the surrounding natural waters. The dominant fish family in the mussel farm was Sciaenidae, which includes several economically valuable species and could be a target for resource conservation. Additionally, the mussel farm hosted numerous migratory fish species exhibiting clear seasonal patterns, suggesting that the farm serves as an important ecological corridor utilized by these species throughout their life cycles.

The effects of Mid-Holocene foragers on the European oyster in Denmark

Oysters (Ostreidae) play a pivotal role in the health and productivity of marine ecosystems. Their unique ability to filter water, provide habitat, and contribute to nutrient cycling has remained underused in many parts of Europe following the destruction of vast oyster beds in the 19th and 20th centuries. The burgeoning field of oyster restoration for aquaculture has recognized the potential of these bivalves in promoting ecosystem resilience and enhancing biodiversity. Restoring oysters to previous levels requires the establishment of ecological baselines that ideally take into account the long-term changes of animal behavior as well as the surrounding environment prior to significant human intervention, an extremely challenging task. Archaeological shell middens are invaluable baseline archives and provide exclusive insights into past ecosystems. Here, we use demographic information from over 2,000 analyzed European oyster (Ostrea edulis) shells dating from ~5,660 to 2,600 cal BCE (calibrated years BCE), the largest archaeological growth rate dataset of mollusks yet. Through the analysis of size as well as ontogenetic age, we decouple anthropogenic from environmental impacts throughout Denmark. Our data show definitive influence of oyster size-age structure through human harvesting during the Mid-Holocene, with older oysters in the Mesolithic (mean: 4.9 y) than the Neolithic (mean: 3.7 y), irrespective of changes in growth rate. Furthermore, we present the metrics for long-term sustainable harvesting of oysters across environmental and socioeconomic transitions, providing demographic targets for current oyster restoration projects and valuable context in mitigating the impact of modern climatic change.

Historical dataset details the distribution, extent and form of lost Ostrea edulis reef ecosystems

Ocean ecosystems have been subjected to anthropogenic influences for centuries, but the scale of past ecosystem changes is often unknown. For centuries, the European flat oyster (Ostrea edulis), an ecosystem engineer providing biogenic reef habitats, was a culturally and economically significant source of food and trade. These reef habitats are now functionally extinct, and almost no memory of where or at what scales this ecosystem once existed, or its past form, remains. The described datasets present qualitative and quantitative extracts from written records published between 1524 and 2022. These show: (1) locations of past flat oyster fisheries and/or oyster reef habitat described across its biogeographical range, with associated levels of confidence; (2) reported extent of past oyster reef habitats, and; (3) species associated with these habitats. These datasets will be of use to inform accelerating flat oyster restoration activities, to establish reference models for anchoring adaptive management of restoration action, and in contributing to global efforts to recover records on the hidden history of anthropogenic-driven ocean ecosystem degradation.

Kelp forests versus urchin barrens: a comparison of ecosystem functions and services provided by two alternative stable marine habitats

Kelp forests and urchin barrens are two stable states in rocky reef ecosystems, each providing unique ecosystem functions like habitat for marine species and primary production. While studies frequently show that kelp forests support higher levels of some ecosystem functions than urchin barren habitats, no research has yet compared average differences. To address this gap, we first conducted a meta-analysis of studies that directly compared the ecosystem functions, services and general attributes provided by each habitat. We also compiled individual studies on ecosystem properties from both habitats and qualitatively assessed the benefits provided. The meta-analysis included 388 observations from 55 studies across 14 countries. We found that kelp forests consistently delivered higher levels of ecosystem properties such as biodiversity, species richness, abalone abundance and sea urchin roe quality. Urchin barrens supported higher urchin density and crustose coralline algae cover. The qualitative review further supported these findings, showing that kelp forests ranked higher in 11 out of 15 ecosystem properties. These findings can help guide decisions on managing rocky reef habitats and demonstrate the benefits of preserving or expanding kelp forests.

Chatting behind the reef: Fish bioacoustic diversity of tropical back-reefs in Fiji, South Pacific

Back-reef habitats are important and fragile transition zones acting as nurseries for many coral reef fishes. In this framework, Passive Acoustic Monitoring (PAM) can be an important tool to evaluate the diversity and dynamics of sonic fish community. Here, we investigated the diversity, spatial and diel dynamics of fish sounds in back-reef habitats at Makogai Island in Fiji, South Pacific. Synchronized underwater recorders were deployed in 4 bays collecting data for about 4 days. The abundance of 12 different sub-categories of fish sounds were quantified. Signals were acoustically characterized and the level of discrimination between the sub-categories was evaluated by Discrimination Function Analysis. Generalized Additive Models showed that the abundance of signals was related to the bay and the hour. Moreover, the Shannon Diversity and Equitability Indices were calculated using acoustic and visual census data to describe fish biodiversity of each bay. The two bays with greater biodiversity based on visual census also showed a greater acoustic diversity at dawn and night. Our results highlight the importance of PAM to reveal the diversity of fish community in back-reef habitats, providing a baseline to understand future changes in these crucial environments.

Pathology of tissue loss in three key gorgonian species in the Mediterranean Sea

The Mediterranean is known for its marine biodiversity, especially gorgonian forests. Unfortunately, these are experiencing rapid declines due to climate change, manifested by repeated marine heat waves resulting in mass mortality events since the early 1990 s. To better understand why gorgonians are declining, more systematic approaches to investigate the exact causes are needed, and pathology may aid in this goal. We described gross and microscopic pathology of tissue loss in three key gorgonian species in the Mediterranean region, Paramuricea clavata, Eunicella cavolini, and Leptogorgia sarmentosa, that were all experiencing various degrees of acute to subacute tissue loss characterized by exposed axial skeleton sometimes partly colonized by epibionts and thinning of adjacent tissues. The most significant variety of lesions was seen in P. clavata followed by L. sarmentosa and E. cavolini. For all species, dissociation of gastrodermal cells was the dominant microscopic lesion followed by necrosis of the gastrodermis. Ciliates invading gastrodermis and associated with necrosis of polyps were seen only in E. cavolini. Epidermal tissue loss was seen only in L. sarmentosa, while P. clavata was distinguished by a prominent inflammatory response and unidentified dark round structures within the tentacle epidermis and gastrodermis with no host response. Further work to understand the cause of death in gorgonians is needed, particularly to elucidate the role of ciliates and environmental co-factors or infectious agents not visible on light microscopy, as well as applications of additional tools such as cytology.

The productivity-stability trade-off in global food systems

Historically, humans have managed food systems to maximize productivity. This pursuit has drastically modified terrestrial and aquatic ecosystems globally by reducing species diversity and body size while creating very productive, yet homogenized, environments. Such changes alter the structure and function of ecosystems in ways that ultimately erode their stability. This productivity-stability trade-off has largely been ignored in discussions around global food security. Here, we synthesize empirical and theoretical literature to demonstrate the existence of the productivity-stability trade-off and argue the need for its explicit incorporation in the sustainable management of food systems. We first explore the history of human management of food systems, its impacts on average body size within and across species and food web stability. We then demonstrate how reductions in body size are symptomatic of a broader biotic homogenization and rewiring of food webs. We show how this biotic homogenization decompartmentalizes interactions among energy channels and increases energy flux within the food web in ways that threaten their stability. We end by synthesizing large-scale ecological studies to demonstrate the prevalence of the productivity-stability trade-off. We conclude that management strategies promoting landscape heterogeneity and maintenance of key food web structures are critical to sustainable food production.

Combining Morphological Characteristics and DNA Barcoding Techniques Confirm Sea Urchins of the Genus Echinometra (Echinodermata: Echinoidea) in Marine Habitat Located at Extreme Regions of the Caribbean Sea

Echinometra spp. are pantropical echinoids found in benthic marine habitat throughout the Caribbean, Atlantic, and Indo-West Pacific oceanic regions. Currently, morphology and molecular data are sparse for echinoids observed along the northeastern coast of Toco, Trinidad, where they are relatively common. Additionally, accurate species identity for Echinometra spp. remains dynamic at both northernmost and southernmost parts of the Caribbean Sea. Although distribution of sea urchins in the genus Echinometra have extensively been studied throughout the Atlantic and Indo-West Pacific, information on its range of distribution at the edge of the Caribbean Sea is lacking. In this study, the mitochondrial Cytochrome c Oxidase subunit I (mt COI) gene was amplified using polymerase chain reaction, then sequenced. Based on successfully obtained gene sequences for 581 base pairs, the echinoid species Echinometra lucunter and Echinometra viridis were identified for black and red color morphotypes from Trinidad (n = 23) and Key Largo, Florida (n = 6), respectively. Furthermore, these specimens were genetically identical to species identified in other studies for Puerto Rico, Panamá, Honduras, and Belize. Although morphological variations, such as spine and test color occur throughout Echinometra spp., molecular identification using the barcoding technique confirmed E. lucunter color morphs for the first time in Trinidad. Since the status of E. lucunter populations, specifically at the most northern and southern regions of the Caribbean Sea is dynamic, further studies using gene markers are essential in determining species distribution, in light of current trends in climate change.

Why aquaculture may not conserve wild fish

We review literature on the displacement paradox and the Jevons paradox, with consideration of their implications for the potential effects of aquaculture on wild fisheries. The Jevons paradox refers to circumstances where improvements in the efficiency of resource use lead to growth in consumption and therefore undermine conservation. The displacement paradox refers to circumstances where increasing use of a potential substitute for a resource (e.g., farmed fish) does not lead to proportionate reduction in consumption of the other resource (e.g., wild fish). The literature on the displacement paradox and the Jevons paradox suggests that there may be unanticipated consequences from the rise of aquaculture that may be detrimental for fisheries conservation. Here, we present theoretical explanations, drawing on the tragedy of the commodity, for understanding the tendencies for these technological paradoxes to occur and emphasize their relevance for concerns associated with fisheries and aquaculture systems.

Anthropogenic activity shapes the assemble and co-occurrence pattern of microbial communities in fishing harbors around the Bohai economic circle

This study aimed to elucidate the effects of coastal environmental stress on the composition of sediment bacterial communities and their cooccurrence patterns in fishing harbors around the Bohai Economic Circle, China. Compared with the natural sea area, fishing harbors contained higher levels of organic pollution (organic pollution index = 0.12 ± 0.026) and considerably reduced bacterial richness and evenness. The distributions of sediment microbial communities clustered along the pollutant concentration gradients across fishing harbors. Betaproteobacteria dominated (76%) organically polluted fishing harbors, which were mostly disturbed by anthropogenic activities. However, the harbors also revealed the absence of numerous pathogenic (Coxiella and Legionella) and photosynthetic (Synechococcus and Leptolyngbya) bacteria. Abundant genera, including Thiobacillus and Arenimonas, exhibited a positive correlation with total phosphorus and a negative correlation with total nitrogen in sediments. Meanwhile, Sulfurovum, Psychrobacter, and Woeseia showed the opposite trend. Pollutant accumulation and anthropogenic activities caused the decrease in the sediment microbial diversity and dispersal ability and promoted convergent evolution. Severely polluted harbors with simplified cooccurrence networks revealed the presence of destabilized microbial communities. In addition, the modularity of bacterial networks decreased with organic pollution. Our results provide important insights into the adjustment mechanism of microbial communities to community organization and functions under environmental pollution stress. Overall, this study enhanced our understanding of how microbial communities in coastal sediments adapted and survived amidst anthropogenic activities like oily effluent discharges from large ships, wash water, domestic sewage, garbage, and fisheries wastes. It also examined their resilience to future contamination.

Erosion of fish trophic position: an indirect effect of fishing on food webs elucidated by stable isotopes

Fishing has significant trophodynamic impacts on marine communities, including reductions in the mean trophic position (TP) of the ecosystem resulting from a decrease in the abundance and size of species and individuals with high TPs. This study demonstrates the erosion of fish TP, an additional process that results in lower TP of individuals of a given size, which may exacerbate the effects of fishing on the food web. A stable isotope approach based on the tRophicPosition Bayesian method was used to quantify the TP of 12 target marine species at a given length, and compare their TP between fishery-restricted areas and trawled areas. The results show a difference in the TP of six benthic and apical nekto-benthic predators, which feed in the median at about 0.5 TP lower in trawled areas. It appears that current 'fishing down marine food webs' analyses may underestimate the trophic effects of fishing. Accounting for changes in trophodynamics of individuals at a given size is important to detect indirect effects through food web interactions. The application of a trawling ban may lead to the restoration of lost trophic structure; however, trophic changes may occur more slowly than changes in biomass. This article is part of the theme issue 'Connected interactions: enriching food web research by spatial and social interactions'.

Coral Reef Water Microbial Communities of Jardines de la Reina, Cuba

Globally, coral reef ecosystems are undergoing significant change related to climate change and anthropogenic activities. Yet, the Cuban archipelago of Jardines de la Reina (JR) has experienced fewer stressors due to its geographical remoteness and high level of conservation. This study examines the surface and benthic reef water microbial communities associated with 32 reef sites along the JR archipelago and explores the relationship between the community composition of reef microorganisms examined using bacterial and archaeal small subunit ribosomal RNA gene (16S rRNA gene) sequencing compared to geographic, conservation/protection level, environmental, physicochemical, and reef benthic and pelagic community features. Reef nutrient concentrations were low and microbial communities dominated by picocyanobacteria and SAR11 and SAR86 clade bacteria, characteristic of an oligotrophic system. Reef water microbial community alpha and beta diversity both varied throughout the archipelago and were strongly related to geography. Three sites in the western archipelago showed unique microbial communities, which may be related to the hydrogeography and influences of the channels linking the Ana Maria gulf with the Caribbean Sea. Overall, this work provides the first extensive description of the reef microbial ecology of the Caribbean's 'Crown Jewel' reef system and a framework to evaluate the influence of ongoing stressors on the reef microorganisms.

Human-driven breakdown of predator-prey interactions in the northern Adriatic Sea

Long-term baseline data that allow tracking how predator-prey interactions have responded to intensifying human impacts are often lacking. Here, we assess temporal changes in benthic community composition and interactions between drilling predatory gastropods and their molluscan prey using the Holocene fossil record of the shallow northern Adriatic Sea, which is characterized by a long history of human transformation. Molluscan assemblages differ between the Isonzo and Po prodelta, but both show consistent temporal trends in the abundance of dominant species. Samples of mollusc prey collected at high stratigraphic resolution indicate that drilling frequencies have drastically declined in the Po prodelta since the mid-twentieth century, while a weaker trend in the more condensed sediments of the Isonzo prodelta is not statistically significant. The decrease in drilling predation intensity and the community turnover are linked to the loss of predatory gastropods and the increased relative abundance of less-preferred prey during the most recent decades. Our results align with data showing the substantial depletion of marine resources at higher trophic levels in the region and indicate that the strong simplification of the food web initiated in the late nineteenth century accelerated further since the mid-twentieth century.

Comprehensive DNA metabarcoding-based detection of non-indigenous invertebrates in recreational marinas through a multi-substrate approach

eDNA metabarcoding has been increasingly employed in the monitoring of marine invertebrate non-indigenous species (NIS), in particular using filtered seawater. However, comprehensive detection of all NIS may require a diversity of sampling substrates. To assess the effectiveness of 5 sample types (hard and artificial substrates, water, zooplankton) on the recovery of invertebrates' diversity, two marinas were monitored over three time points, using COI and 18S rRNA genes as DNA metabarcoding markers. We detected a total of 628 species and 23 NIS, with only up to 9% species and 17% of NIS detected by all sample types. Hard and artificial substrates were similar to each other but displayed the most significant difference in invertebrate recovery when compared to water eDNA and zooplankton. Five NIS are potential first records for Portugal. No NIS were detected in all sample types and seasons, highlighting the need for varied sampling approaches, and consideration of temporal variation for comprehensive marine NIS surveillance.

Feeding biology of crown-of-thorns seastars across sites differing in Acropora availability

Crown-of-thorns seastars (COTS, Acanthaster spp.) are a major contributor to coral mortality across the Indo-Pacific and can cause extensive reef degradation. The diet preferences of COTS can influence coral community structure by predation on fast-growing genera such as Acropora and avoidance of rare coral genera. In non-outbreaking populations, this preference can increase species diversity. The feeding biology of Acanthaster cf. solaris was compared at two sites (Shark Alley and Second Lagoon) on One Tree Island reef, located in the southern Great Barrier Reef, to determine whether the availability of Acropora influences differences in COTS movement, feeding preference and feeding rates within the same reef system. Acanthaster cf. solaris were tracked daily for five days across both sites, with measurements of movement, feeding scars and coral composition recorded over this time. While Shark Alley and Second Lagoon have similar live coral cover (40 and 44 % respectively), Shark Alley has significantly lower Acropora availability than Second Lagoon (2 vs 32 %). The feeding rate of COTS was significantly different between Shark Alley and Second Lagoon (259.8 and 733.8 cm2 of coral per day, respectively), but did not differ between seastar size (25-40 cm and >40 cm). Acanthaster cf. solaris showed preference for Pocillopora, Seriatopora, Acropora and Isopora and an avoidance of Porites at both sites. The results suggest that for coral reef sites where Acropora is not dominant, COTS outbreaks may be less likely to initiate, with comparatively low feeding rates found in comparison to coral reefs where Acropora is dominant.

The global extent and severity of operational interactions between conflicting pinnipeds and fisheries

Recent population recovery of many pinniped species (seals, sea lions, walrus) is a conservation success. However, pinniped population recovery combined with increasing global fisheries operations is leading to increased conflicts between pinnipeds and fisheries. This human-wildlife conflict threatens pinniped conservation outcomes and may impose damaging impacts on fisheries, but the economic consequences and extent of these impacts are poorly understood. Here, we provide a global assessment of pinniped and fisheries operational interactions. We show that a third of reported fishing days have interactions with pinnipeds and 13.8% of catch is lost. Our results also reveal high heterogeneity between studies. Small-scale fisheries are three times more likely to interact with pinnipeds and lose four times as much catch as large-scale fisheries. Finally, we develop a spatial index that can predict where conflict is most likely to occur. Our findings reveal a substantial global issue requiring appropriate management as pinniped populations continue to recover.

The global distribution and climate resilience of marine heterotrophic prokaryotes

Heterotrophic Bacteria and Archaea (prokaryotes) are a major component of marine food webs and global biogeochemical cycles. Yet, there is limited understanding about how prokaryotes vary across global environmental gradients, and how their global abundance and metabolic activity (production and respiration) may be affected by climate change. Using global datasets of prokaryotic abundance, cell carbon and metabolic activity we reveal that mean prokaryotic biomass varies by just under 3-fold across the global surface ocean, while total prokaryotic metabolic activity increases by more than one order of magnitude from polar to tropical coastal and upwelling regions. Under climate change, global prokaryotic biomass in surface waters is projected to decline ~1.5% per °C of warming, while prokaryotic respiration will increase ~3.5% ( ~ 0.85 Pg C yr-1). The rate of prokaryotic biomass decline is one-third that of zooplankton and fish, while the rate of increase in prokaryotic respiration is double. This suggests that future, warmer oceans could be increasingly dominated by prokaryotes, diverting a growing proportion of primary production into microbial food webs and away from higher trophic levels as well as reducing the capacity of the deep ocean to sequester carbon, all else being equal.

Deep antiquity of seagrasses supporting European eel fisheries in the western Baltic

Protecting ocean habitats is critical for international efforts to mitigate climate impacts and ensure food security, but the ecological data upon which policy makers base conservation and restoration targets often reflect ecosystems that have already been deeply impacted by anthropogenic change. The archaeological record is a biomolecular archive offering a temporal scope that cannot be gathered from historical records or contemporary fieldwork. Insights from biogeochemical and osteometric analyses of fish bones, combined with context from contemporary field studies, show how prehistoric fisheries in the western Baltic relied on seagrass meadows. European eels (Anguilla anguilla) harvested by Mesolithic and Neolithic peoples over millennia showed a strong fidelity for eelgrass foraging habitats, an ecological relationship that remains largely overlooked today, demonstrating the value of protecting these habitats. These data open new windows onto ecosystem- and species-level behaviours, highlighting the need for wider incorporation of archaeological data in strategies for protecting our oceans.