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We used lipid, fatty acid, and stable isotope analyses to investigate variation, over nine months, in the trophodynamics of 10 dominant cryptofaunal, macroalgal/algal, and environmental components from two sites within a rhodolith (Lithothamnion glaciale) bed in southeastern Newfoundland (Canada). There was an overall shift from a diatom-based food web following the spring phytoplankton bloom to a kelp/algae-based food web during fall, accompanied by preferred use of EPA (20:5ω3) over DHA (22:6ω3) in most cryptofauna. The food web contained three trophic levels that encompassed: (1) direct feeding relationships from primary producers (e.g., rhodoliths, macroalgae) to second-order consumers (e.g., sea stars, polychaetes); (2) trophic subsidy from within and outside the rhodolith bed via settlement, resuspension, and consumption of macroalgal fragments and other detrital organic matter; and (3) strong pelagic/benthic coupling. Riverine input did not affect cryptofaunal diets, as shown by the lack of terrestrial biomarkers at the study site nearest to the riverine input, and there were minor differences in trophodynamics between both study sites. The present study's findings, applicable to relatively broad spatial and temporal domains, as well as those of complementary studies of the same rhodolith bed, uncover high spatio-temporal stability of the rhodolith bed framework and of resident cryptofaunal abundance, diversity, and trophodynamics. [ABSTRACT FROM AUTHOR]

The present study provides new insight into the key aspects of the early formative period of the ecosystem concept in aquatic ecology. Raymond Lindeman's trophodynamics is known to be a starting point for the development of the modern concept of ecosystem. The trophodynamic approach in ecology was proposed by Lindeman in his widely cited paper of 1942. Lindeman's views are analyzed in comparison with the contemporary production studies in aquatic ecology. It is shown that a similar theoretical system has been proposed in the USSR at the end of the 1930s by Georgiy G. Vinberg. He introduced the concept of biotic balance based on the wide appraisal of the dark and light bottles method. The study shows that both Lindeman's trophodynamics and Vinberg's concept of biotic balance relied on an energy-based approach in considering the wholeness of a water body. The two scientists, however, differed in several important aspects concerning the interpretation of the role of living organisms. The holistic interpretation of ecosystem by Lindeman and Vinberg can be seen as part of the dilemma between physicalism and organicism. At the same time, the main emphasis in the concepts of both Vinberg and Lindemann was on the primary production component, a feature that was common to the first holistic systems in production hydrobiology (e.g., E. Naumann's regional limnology). It is clear that modern problems of aquatic ecology should be addressed from the perspective of the organismocentric understanding of the ecosystem, but undoubtedly at the new level of development of this view. [ABSTRACT FROM AUTHOR]

IntroductionIn the Southern Ocean, myctophids are the most successful pelagic fish group in terms of diversity, biomass, and abundance. They play a crucial role in linking primary consumers and coupling carbon flux between surface and mesopelagic depths. Understanding their trophodynamics is key to assessing pelagic ecosystem resilience under environmental change. Conventional stomach content analyses indicate that myctophids predominantly feed on crustaceans, such as copepods and euphausiids, but are less effective at detecting easily digestible, soft-bodied organisms like gelatinous zooplankton (GZP) and pteropods. MethodsThis study used multimarker (COI Leray-XT and 18S v1-v2) DNA metabarcoding to analyze the diets of two abundant myctophids in the Scotia Sea, Electrona antarctica and Electrona carlsbergi.Results and discussionWe found a diverse diet dominated by copepods and euphausiids, followed by pteropods and GZP in terms of frequency of occurrence and relative read abundances. Within the GZP, salps and appendicularians were major components of the diet for E. carlsbergi, while hydrozoans were prominent in E. antarctica. With regards seasonal and spatial variability in the dietary contribution of GZP, E. carlsbergi consumed primarily appendicularians, chaetognaths, and hydrozoans during spring (2006) in the northern region, and more salps (predominantly Ilhea racovitzai) and other cnidarians in autumn (2009) in the southern region. Our study reveals the dietary diversity of myctophid fish as well as the importance GZP consumption as a key trophic pathway in the Southern Ocean.

The yellowfin tuna is a very abundant tropical tuna species in the western equatorial Atlantic Ocean and an important fishery resource for the Brazilian tuna fleet. In this study we performed stable isotope analysis to better understand the spatial trophodynamics and dietary changes in yellowfin tuna around two insular marine protected areas in Brazil. A total of 65 yellowfin tuna specimens measuring between 47 and 138 cm LT (total length) were sampled around the archipelagos of Fernando de Noronha (FNA; n = 34) and Saint Peter and Saint Paul (SPSPA; n = 31) between July 2018 and September 2019. Bayesian mixing models and generalized additive models were used to investigate the contributions of four different prey items (zooplankton, cephalopods, fish larvae, and flying fish) to yellowfin tuna diet in each area and their potential changes in relation to predator growth. The four prey items were found to have different overall contributions between the two studied areas, with zooplankton being the most important prey in FNA, whereas flying fish was the most relevant prey to the species' diet in SPSPA. Significant changes in the species diet by size were also found, with fish smaller than 90 cm (TL) having a more generalist diet and larger animals relying more on consuming larger and more nutritious prey (i.e., flying fish). Our results suggest that these two marine protected areas play an important role in ocean dynamics, providing important and different foraging grounds for the development of this predator species. [ABSTRACT FROM AUTHOR]

We used lipid, fatty acid, and stable isotope analyses to investigate variation, over nine months, in the trophodynamics of 10 dominant cryptofaunal, macroalgal/algal, and environmental components from two sites within a rhodolith (Lithothamnion glaciale) bed in southeastern Newfoundland (Canada). There was an overall shift from a diatom-based food web following the spring phytoplankton bloom to a kelp/algae-based food web during fall, accompanied by preferred use of EPA (20:5ω3) over DHA (22:6ω3) in most cryptofauna. The food web contained three trophic levels that encompassed: (1) direct feeding relationships from primary producers (e.g., rhodoliths, macroalgae) to second-order consumers (e.g., sea stars, polychaetes); (2) trophic subsidy from within and outside the rhodolith bed via settlement, resuspension, and consumption of macroalgal fragments and other detrital organic matter; and (3) strong pelagic/benthic coupling. Riverine input did not affect cryptofaunal diets, as shown by the lack of terrestrial biomarkers at the study site nearest to the riverine input, and there were minor differences in trophodynamics between both study sites. The present study’s findings, applicable to relatively broad spatial and temporal domains, as well as those of complementary studies of the same rhodolith bed, uncover high spatio-temporal stability of the rhodolith bed framework and of resident cryptofaunal abundance, diversity, and trophodynamics.

Coral reefs are biodiverse ecosystems that rely on trophodynamic transfers from primary producers to consumers through the detrital pathway. The sponge loop hypothesis proposes that sponges consume dissolved organic carbon (DOC) and produce large quantities of detritus on coral reefs, with this turn-over approaching the daily gross primary production of the reef ecosystem. In this study, we collected samples of detritus in the epilithic algal matrix (EAM) and samples from potential sources of detritus over two seasons from the forereef at Carrie Bow Cay, Belize. We chose this location to maximize the likelihood of finding support for the sponge loop hypothesis because Caribbean reefs have higher sponge abundances than other tropical reefs worldwide and the Mesoamerican barrier reef is an archetypal coral reef ecosystem. We used stable isotope analyses and eDNA metabarcoding to determine the composition of the detritus. We determined that the EAM detritus was derived from a variety of benthic and pelagic sources, with primary producers (micro- and macroalgae) as major contributors and metazoans (Arthropoda, Porifera, Cnidaria, Mollusca) as minor contributors. None of the sponge species that reportedly produce detritus were present in EAM detritus. The cnidarian signature in EAM detritus was dominated by octocorals, with a scarcity of hard corals. The composition of detritus also varied seasonally. The negligible contribution of sponges to reef detritus contrasts with the detrital pathway originally proposed in the sponge loop hypothesis. The findings indicate a mix of pelagic and benthic sources in the calmer summer and primarily benthic sources in the more turbulent spring. [ABSTRACT FROM AUTHOR]

Coral reefs are biodiverse ecosystems that rely on trophodynamic transfers from primary producers to consumers through the detrital pathway. The sponge loop hypothesis proposes that sponges consume dissolved organic carbon (DOC) and produce large quantities of detritus on coral reefs, with this turn-over approaching the daily gross primary production of the reef ecosystem. In this study, we collected samples of detritus in the epilithic algal matrix (EAM) and samples from potential sources of detritus over two seasons from the forereef at Carrie Bow Cay, Belize. We chose this location to maximize the likelihood of finding support for the sponge loop hypothesis because Caribbean reefs have higher sponge abundances than other tropical reefs worldwide and the Mesoamerican barrier reef is an archetypal coral reef ecosystem. We used stable isotope analyses and eDNA metabarcoding to determine the composition of the detritus. We determined that the EAM detritus was derived from a variety of benthic and pelagic sources, with primary producers (micro- and macroalgae) as major contributors and metazoans (Arthropoda, Porifera, Cnidaria, Mollusca) as minor contributors. None of the sponge species that reportedly produce detritus were present in EAM detritus. The cnidarian signature in EAM detritus was dominated by octocorals, with a scarcity of hard corals. The composition of detritus also varied seasonally. The negligible contribution of sponges to reef detritus contrasts with the detrital pathway originally proposed in the sponge loop hypothesis. The findings indicate a mix of pelagic and benthic sources in the calmer summer and primarily benthic sources in the more turbulent spring.

Documenting long‐term changes in the trophic structure of food webs and how species respond to these changes is essential to forecast their vulnerability and resilience to environmental stressors. Over the past decades, the St. Lawrence marine ecosystem (Canada) has experienced major changes in its physical, chemical, and biological conditions from overfishing, acoustic and chemical pollution, climate change, and the increased abundance of some top predators. These changes have likely affected the trophodynamics of the ecosystem, and are suspected to have deleterious effects on endangered species of mammals and other components of the ecosystem, such as blue whales (Balaenoptera musculus), fin whales (B. physalus), and beluga (Delphinapterus leucas). This study examined the trophic structure of the St. Lawrence marine ecosystem, including the isotopic niche of various species, over two periods of contrasting pressures from anthropogenic and climatic stressors (1995–2003 vs. 2019–2021). Stable isotope ratios were measured in 1240 samples of 21 species of marine invertebrates, fishes, and mammals sampled during both periods. A significant change in the isotopic value and niche position between periods is observed in most of the sampled species. While the direction of change and effect size were not uniform among species, these changes confirmed that substantial modifications in community structure have occurred over time. Niche overlap decreased considerably among some of the pelagic and demersal fishes, and among whale species during the most recent period. Combined with a concomitant reduction in niche breadth in several species, these observations suggested that resource sharing was limited among these species. This study highlighted some degree of dietary plasticity in several species, and a long‐term change in the trophic structure of the St. Lawrence marine ecosystem, with likely effects on diet composition and energetics of several populations, including endangered species. [ABSTRACT FROM AUTHOR]

The notion that closely related species resemble each other in ecological niche space (i.e., phylogenetic dependence) has been a long-standing, contentious paradigm in evolutionary biology, the incidence of which is important for predicting the ecosystem-level effects of species loss. Despite being examined across a multitude of terrestrial taxa, many aspects of niche conservatism have yet to be explored in marine species, especially for characteristics related to resource use and trophic behavior (Eltonian niche characteristics, ENCs). We combined ENCs derived from stable isotope ratios at assemblage- and species-levels with phylogenetic comparative methods, to test the hypotheses that benthic marine fishes (1) exhibit similar assemblage-wide ENCs regardless of geographic location and (2) display phylogenetically dependent ENCs at the species level. We used a 12-species sub-set of the monophyletic group Rajidae sampled from three independent assemblages (Central California, Gulf of Alaska, and Northwest Atlantic), which span two ocean basins. Assemblage-level ENCs implied low trophic diversity and high evenness, suggesting that Rajidae assemblages may exhibit a well-defined trophic role, a trend consistent regardless of geographic location. At the species level, we found evidence for phylogenetic dependence of ENCs relating to trophic diversity (i.e., isotopic niche width; SEAc). Whether individuals can be considered functional equivalents across assemblages is hard to ascertain because we did not detect a significant phylogenetic signal for ENCs relating to trophic function (e.g., trophic position). Thus, additional, complimentary approaches are required to further examine the phylogenetic dependence of species functionality. Our approach illustrates the potential of stable isotope-derived niche characteristics to provide insight on macroecological processes occurring across evolutionary time, which could help predict how assemblages may respond to the effects of species loss.

Abstract Documenting long‐term changes in the trophic structure of food webs and how species respond to these changes is essential to forecast their vulnerability and resilience to environmental stressors. Over the past decades, the St. Lawrence marine ecosystem (Canada) has experienced major changes in its physical, chemical, and biological conditions from overfishing, acoustic and chemical pollution, climate change, and the increased abundance of some top predators. These changes have likely affected the trophodynamics of the ecosystem, and are suspected to have deleterious effects on endangered species of mammals and other components of the ecosystem, such as blue whales (Balaenoptera musculus), fin whales (B. physalus), and beluga (Delphinapterus leucas). This study examined the trophic structure of the St. Lawrence marine ecosystem, including the isotopic niche of various species, over two periods of contrasting pressures from anthropogenic and climatic stressors (1995–2003 vs. 2019–2021). Stable isotope ratios were measured in 1240 samples of 21 species of marine invertebrates, fishes, and mammals sampled during both periods. A significant change in the isotopic value and niche position between periods is observed in most of the sampled species. While the direction of change and effect size were not uniform among species, these changes confirmed that substantial modifications in community structure have occurred over time. Niche overlap decreased considerably among some of the pelagic and demersal fishes, and among whale species during the most recent period. Combined with a concomitant reduction in niche breadth in several species, these observations suggested that resource sharing was limited among these species. This study highlighted some degree of dietary plasticity in several species, and a long‐term change in the trophic structure of the St. Lawrence marine ecosystem, with likely effects on diet composition and energetics of several populations, including endangered species.

Variation in hydrological connectivity (HC) between rivers and lakes gives rise to periodic large water level fluctuation (WLF) in river-connected lakes (RCL). However, how WLF shapes the material cycling and concomitant trophodynamics of RCL remain unclear. Here we evaluated the resource availability, relative contributions of autochthonous and allochthonous carbon sources (by Bayesian mixing models) and trophic structure (using δ13C and δ15N) of Lake Poyang, the largest freshwater lake in China, during different hydrological periods. Terrestrial C3 plants in the aquatic/terrestrial transition zones (ATTZ) were the main supporter of aquatic consumers all year round. Compared with historical data, the contributions of autochthonous production to aquatic food webs were low. This is primarily ascribed to the influences of hydrological regimes in that the operation of Three Gorges Dam and HC changed the rhythm of WLF in Lake Poyang, restricting the production of aquatic vegetation and epiphytic algae. Most common fish species indicated higher trophic positions (TPs) during the dry than wet season, but only eleven of thirty-six common species showed a statistically significant increase (p

Forage fishes are a critical food web link in marine ecosystems, aggregating in a hierarchical patch structure over multiple spatial and temporal scales. Surface‐level forage fish aggregations (FFAs) represent a concentrated source of prey available to surface‐ and shallow‐foraging marine predators. Existing survey and analysis methods are often imperfect for studying forage fishes at scales appropriate to foraging predators, making it difficult to quantify predator–prey interactions. In many cases, general distributions of forage fish species are known; however, these may not represent surface‐level prey availability to predators. Likewise, we lack an understanding of the oceanographic drivers of spatial patterns of prey aggregation and availability or forage fish community patterns. Specifically, we applied Bayesian joint species distribution models to bottom trawl survey data to assess species‐ and community‐level forage fish distribution patterns across the US Northeast Continental Shelf (NES) ecosystem. Aerial digital surveys gathered data on surface FFAs at two project sites within the NES, which we used in a spatially explicit hierarchical Bayesian model to estimate the abundance and size of surface FFAs. We used these models to examine the oceanographic drivers of forage fish distributions and aggregations. Our results suggest that, in the NES, regions of high community species richness are spatially consistent with regions of high surface FFA abundance. Bathymetric depth drove both patterns, while subsurface features, such as mixed layer depth, primarily influenced aggregation behavior and surface features, such as sea surface temperature, sub‐mesoscale eddies, and fronts influenced forage fish diversity. In combination, these models help quantify the availability of forage fishes to marine predators and represent a novel application of spatial models to aerial digital survey data. [ABSTRACT FROM AUTHOR]

Euphausia superba and Thysanoessa macrura are dominant krill species in the Southern Ocean and their habitats are often overlapped reportedly. Studies of the feeding strategies of these two krill species will help us better understand the coexistence mechanisms and estimate the roles that krill played in the food web of the Southern Ocean. The trophodynamics of E. superba and T. macrura at different ontogenetic stages (furcilia, juvenile, adult) were studied using fatty acid and stable isotope biomarkers in the samples collected in Amundsen Sea during austral summer of 2017/2018 and 2018/2019. Diatoms like Fragilariopsis spp. was the most abundant phytoplankton species in the summer of 2017/2018, while the abundance of phytoplankton in the summer of 2018/2019 was dominated by Phaeocystis sp. The gradual increase of the carnivorous index 18:1n–9/18:1n–7 with ontogeny of both species in 2018/2019 indicated more carnivorous feeding of adults compared with juveniles and larvae. Meanwhile, greater δ15N values of T. macrura than that of E. superba were more significant in the juvenile and adult stages during the summer of 2018/2019. Our results indicate that the trophic niche differentiation between the two krill species appeared in postlarval stage and can be influenced by food availability. Compared with E. superba, T. macrura was more prone to feed omnivorously or carnivorously responding to food availability. [ABSTRACT FROM AUTHOR]

Understanding the spatiotemporal dynamics of trophic structures, or trophodynamics, is important for assessing the overall condition and function of estuarine ecosystems. We examined spatial and seasonal trophodynamics of nekton assemblages across the seascape of a subtropical estuary (Charlotte Harbor, FL, USA) using historical nekton data from an ongoing monitoring program. We also examined relationships between trophodynamics and the spatial distribution of vegetated habitats, such as salt marshes, mangroves, and seagrass beds, as well as their absence along hardened shorelines (seawalls or riprap) using seascape metrics (area and edge density of habitats within several search radii of sample locations). We found that nekton assemblages in shallow waters (from the shoreline to a depth of ≤ 1.5 m) transitioned from mainly planktivores in the lower Peace and Myakka Rivers to mainly benthivores (those feeding on benthic infauna, epifauna, or seagrass) in the middle and lower portions of Charlotte Harbor. Overall nekton assemblages throughout the estuary appeared to be largely sustained through benthic pathways in areas with abundant seagrass and nearby mangrove habitat, particularly during the cool-dry winter when planktivore densities were seasonally low. The dramatic seasonal decline in planktivore densities we found in the lower rivers may be related to low freshwater inflow and increased predation resulting from seasonal recruitment pulses of several omnivorous species. Trophodynamics linked with seascape metrics of estuarine habitat structure described here may be used as a spatially explicit baseline of the estuarine seascape to monitor ecosystem health as well as parameterize spatial ecosystem models used in fisheries management in Charlotte Harbor and similar subtropical estuaries. [ABSTRACT FROM AUTHOR]

Abstract Forage fishes are a critical food web link in marine ecosystems, aggregating in a hierarchical patch structure over multiple spatial and temporal scales. Surface‐level forage fish aggregations (FFAs) represent a concentrated source of prey available to surface‐ and shallow‐foraging marine predators. Existing survey and analysis methods are often imperfect for studying forage fishes at scales appropriate to foraging predators, making it difficult to quantify predator–prey interactions. In many cases, general distributions of forage fish species are known; however, these may not represent surface‐level prey availability to predators. Likewise, we lack an understanding of the oceanographic drivers of spatial patterns of prey aggregation and availability or forage fish community patterns. Specifically, we applied Bayesian joint species distribution models to bottom trawl survey data to assess species‐ and community‐level forage fish distribution patterns across the US Northeast Continental Shelf (NES) ecosystem. Aerial digital surveys gathered data on surface FFAs at two project sites within the NES, which we used in a spatially explicit hierarchical Bayesian model to estimate the abundance and size of surface FFAs. We used these models to examine the oceanographic drivers of forage fish distributions and aggregations. Our results suggest that, in the NES, regions of high community species richness are spatially consistent with regions of high surface FFA abundance. Bathymetric depth drove both patterns, while subsurface features, such as mixed layer depth, primarily influenced aggregation behavior and surface features, such as sea surface temperature, sub‐mesoscale eddies, and fronts influenced forage fish diversity. In combination, these models help quantify the availability of forage fishes to marine predators and represent a novel application of spatial models to aerial digital survey data.

The environmental regulation of planktonic food web structure is a key determinant for the efficiency of energy transfer through trophic levels, with direct implications for the amount of energy that is available to top-consumers and deep-sea communities. Yet, the complex trophic interplay between the different components of plankton communities under contrasting environmental conditions remains unresolved. Here, we present a comprehensive field study based on compound-specific isotope analysis of amino acids that aims to explore depth-resolved changes in the trophic strategies of various size-classes of mesozooplankton from distinct habitats across the Southeast Pacific. According to the δ15N values of the so-called source amino acids such as phenylalanine, we first identified a clear shift in nitrogen sources for biological production, from nitrate in the productive upwelling waters of the Humboldt Current System to increased inputs of diazotroph-N within the ultra-oligotrophic South Pacific gyre. These shifts in the productivity and in the source of N at the base of the food web were not accompanied by significant changes in the trophic position (TP) of mesozooplankton, which were mainly omnivores (TP = 2.8 ± 0.3, n = 65) in all ecoregions. However, although the planktonic food web length remained relatively unaltered along the productivity gradient, the microbial contribution to mid-trophic level consumers appeared to be more important at relatively high productivities, likely due to more intense remineralization processes in a late successional stage of the upwelling throughout the coastal-transition zone. Altogether, this research work will contribute to a better understanding of the food web functioning in one of the least explored marine regions of the world’s oceans.

Biodiversity of terrestrial and marine ecosystems, including coral reefs, is dominated by small, often cryptic, invertebrate taxa that play important roles in ecosystem structure and functioning. While cryptofauna community structure is determined by strong small‐scale microhabitat associations, the extent to which ecological and environmental factors shape these communities are largely unknown, as is the relative importance of particular microhabitats in supporting reef trophodynamics from the bottom up.The goal of this study was to address these knowledge gaps, provided coral reefs are increasingly exposed to multiple disturbances and environmental gradients that influence habitat complexity, condition and ecosystem functioning.We compared the density, biomass, size range, phylogenetic diversity and functional roles of motile cryptofauna in Palau, Western Micronesia, among four coral‐derived microhabitats representing various states of degradation (live coral [Acropora and Pocillopora], dead coral and coral rubble) from reefs along a gradient of effluent exposure.In total, 122 families across ten phyla were identified, dominated by the Arthropoda (Crustacea) and Mollusca. Cryptofauna biomass was greatest in live Pocillopora, while coral rubble contained the greatest density and diversity. Size ranges were broader in live corals than both dead coral and rubble. From a bottom‐up perspective, effluent exposure had mixed effects on cryptic communities including a decline in total biomass in rubble. From a top‐down perspective, cryptofauna were generally unaffected by predator biomass.Our data show that, as coral reef ecosystems continue to decline in response to more frequent and severe disturbances, habitats other than live coral may become increasingly important in supporting coral reef biodiversity and food webs. [ABSTRACT FROM AUTHOR]

Food web linkages, or the feeding relationships between species inhabiting a shared ecosystem, are an ecological lens through which ecosystem structure and function can be assessed, and thus are fundamental to informing sustainable resource management. Empirical feeding datasets have traditionally been painstakingly generated from stomach content analysis, direct observations and from biochemical trophic markers (stable isotopes, fatty acids, molecular tools). Each approach carries inherent biases and limitations, as well as advantages. Here, using 27 years (1991-2016) of in situ feeding observations collected by remotely operated vehicles (ROVs), we quantitatively characterize the deep pelagic food web of central California within the California Current, complementing existing studies of diet and trophic interactions with a unique perspective. Seven hundred and forty-three independent feeding events were observed with ROVs from near-surface waters down to depths approaching 4000 m, involving an assemblage of 84 different predators and 82 different prey types, for a total of 242 unique feeding relationships. The greatest diversity of prey was consumed by narcomedusae, followed by physonect siphonophores, ctenophores and cephalopods. We highlight key interactions within the poorly understood 'jelly web', showing the importance of medusae, ctenophores and siphonophores as key predators, whose ecological significance is comparable to large fish and squid species within the central California deep pelagic food web. Gelatinous predators are often thought to comprise relatively inefficient trophic pathways within marine communities, but we build upon previous findings to document their substantial and integral roles in deep pelagic food webs.

Fish have one of the highest occurrences of individual specialization in trophic strategies among Eukaryotes. Yet, few studies characterize this variation during trophic niche analysis, limiting our understanding of aquatic food web dynamics. Stable isotope analysis (SIA) with advanced Bayesian statistics is one way to incorporate this individual trophic variation when quantifying niche size. However, studies using SIA to investigate trophodynamics have mostly focused on species‐ or guild‐level (i.e., assumed similar trophic strategy) analyses in settings where source isotopes are well‐resolved. These parameters are uncommon in an ecological context. Here, we use Stable Isotope Bayesian Ellipses in R (SIBER) to investigate cross‐guild trophodynamics of 11 reef fish species within an oceanic atoll. We compared two‐ (δ15N and δ13C) versus three‐dimensional (δ15N, δ13C, and δ34S) reconstructions of isotopic niche space for interpreting guild‐, species‐, and individual‐level trophic strategies. Reef fish isotope compositions varied significantly among, but also within, guilds. Individuals of the same species did not cluster together based on their isotope values, suggesting within‐species specializations. Furthermore, while two‐dimensional isotopic niches helped differentiate reef fish resource use, niche overlap among species was exceptionally high. The addition of δ34S and the generation of three‐dimensional isotopic niches were needed to further characterize their isotopic niches and better evaluate potential trophic strategies. These data suggest that δ34S may reveal fluctuations in resource availability, which are not detectable using only δ15N and δ13C. We recommend that researchers include δ34S in future aquatic food web studies. [ABSTRACT FROM AUTHOR]

The diet of Gymnocypris species and the food web structure in Lake Langcuo (4300 m above sea level) of the southwest Tibetan Plateau of China were investigated by carbon (δ13C) and nitrogen (δ15N) stable isotope analyses. Ephemeropteran and chironomid larvae were the major components of the diet of Gymnocypris chui, making it an omnivore with animals as the majority component, while the Myriophyllum spicatum and ephemeropteran larvae was the most important for Gymnocypris scleracanthus, qualifying it as an omnivore with plants as the majority component. Ephemeropteran larvae also made up the most abundant constituent of the Triplophysa stoliczkae diet. Overall diet changed during development of G. chui, but the dominant food remained unaltered, whereas the major component of G. scleracanthus diet changed. An average trophic enrichment factor of 3.4‰ was used to calculate the trophic levels based on δ15N, with the results indicated that the food web has three trophic levels: primary producers and primary and secondary consumers. The primary consumer trophic level was represented by zooplankton, aquatic insect larvae, and gammarids, with a mean δ15N value of 7.79‰. The secondary consumer level included all fish, with a mean δ15N value of 10.68‰. The primary consumers were chiefly dependent on autochthonous carbon input. This is the first quantitative study of the food web in a lake of the Tibetan Plateau above 4000 m. The study provides information critical to lake management and conservation in the Tibetan Plateau. [ABSTRACT FROM AUTHOR]

The order of magnitude of biomass and production at various trophic levels in the epipelagic community has been calculated, and the main pathways for the transformation of matter and energy in the Bering Sea have been identified. For each group of aquatic organisms, the average indicators of biomass, production, and grazing (feeding) consumption were estimated. According to long-term average data (1986–2020), 1054.7 million tons C/year of organic matter was produced in epipelagic zone of the Bering Sea at the 1st trophic level, 120.4 million tons C/year, at the 2nd trophic level, 20.7 million tons C/year, at the 3rd trophic level, 0.93 million tons C/year, at the 4th one, 0.015 million tons C/year, at the 5th level. The annual production of aquatic organisms in the epipelagic zone of the Bering Sea is exceeds 1 billion tons C/year (1196.8 million tons C/year) or 21.4 billion tons of wet weight. Excluding primary production, which is 72.6% of gross production in carbon equivalent, microheterotrophs (15.5%) and dominant zooplankton groups (copepods—7.3%, euphausiids—1.9%, chaetognaths—1.1%, and hyperiids—0.5%) contribute most significantly to annual production. The contribution of the functional groups of the nekton (pollock Gadus chalcogrammus, squid, salmon, and mesopelagic fish) is approximately 1–2 orders of magnitude lower. Altogether, the share of the heterotrophic part of the biocenosis in the epipelagic zone of the Bering Sea accounts for about 27% of production. The powerful development of representatives of the 2nd trophic level (mainly copepods and, to a lesser extent, euphausiids) suggests that the level of grazing pressure from planktonic and nektonic predators may be higher. The forage base of the Bering Sea is capable of providing food for nekton stock exceeding the current level. This conclusion is important from the standpoint of the development of grazing aquaculture of valuable pelagic fish, including salmon. [ABSTRACT FROM AUTHOR]

The role of small prey (< 200 µm) in larval marine fish nutrition is largely understudied. Here, we explore the contribution of protozooplankton (PZP 20–200 µm) to larval fish diets, compared to metazoan microzooplankton (MZP 55–200 µm). More specifically, we tested whether the contribution of PZP increased during the low productivity season and decreased as larvae grow. We used North Sea autumn spawning herring (Clupea harengus) as a case study, as it is a key species with high commercial and ecological importance. In autumn and winter, the potential PZP and MZP prey was dominated by cells < 50 µm (mainly Gymnodiniales, Pronoctiluca pelagica,Tripos spp. and Strombidium spp.), while copepod nauplii and copepodites where more abundant in autumn than in winter. Based on their trophic enrichment (∆15 N), larvae preferentially grazed on small MZP < 50 µm rather than PZP both in autumn and winter. Larvae of different body size (range 8–14 mm standard length) fed at the same trophic level but on different prey (similar δ15N but different δ13C). Growth rates (based on RNA/DNA estimates) were similar in autumn and winter, suggesting that growth was not affected by station-specific differences in the composition of the prey field. Our results not only underscore the important role of MZP on larval herring diets both in autumn and wintertime, but also emphasize the limitations of bulk stable isotope analysis. Given the current low recruitment in North Sea herring, these results provide significant information for future monitoring approaches relevant to stock assessment of this species. [ABSTRACT FROM AUTHOR]

The estuarine environments surrounding coastal Louisiana create favorable conditions for microbially mediated mercury (Hg) methylation and subsequent bioaccumulation by biota. In 2010, the Deepwater Horizon (DWH) oil spill released large amounts of oil which, despite having low Hg concentrations, had the potential to influence methylmercury (MeHg) bioavailability in the coastal zone. To explore this possibility, we assessed Hg concentrations and trophodynamics in the coastal Louisiana food web prior to and immediately following the DWH oil spill and compared these metrics with an adjacent coastal ecosystem in the northern Gulf of Mexico. We found no differences in MeHg concentrations between oysters collected in years prior to the spill (1986–2007) and those collected during or in the months immediately after the spill (May to December 2010). When comparing tissue MeHg concentrations and carbon and nitrogen stable isotope values across 13 species of bivalves, shrimp, crabs, fishes, and birds we found evidence of significant biomagnification within the coastal Louisiana food web driven by species’ trophic position and their use of differing basal carbon sources. In addition, Hg trophodynamics also differed between two adjacent coastal ecosystems, post-spill coastal Louisiana (2010) and pre-spill coastal Alabama (2008–2009). While there was a higher trophic magnification factor in coastal Louisiana relative to coastal Alabama, food web baseline MeHg concentrations were higher in coastal Alabama. The high degree of biomagnification in coastal Louisiana, and significant regional variation, underscores the need to monitor Hg trophodynamics over space and time to better evaluate the short and long-term ecological consequences of events like the DWH oil spill.

Lipid and fatty acid datasets are commonly used to assess the nutritional composition of organisms, trophic ecology, and ecosystem dynamics. Lipids and their fatty acid constituents are essential nutrients to all forms of life because they contribute to biological processes such as energy flow and metabolism. Assessment of total lipids in tissues of organisms provides information on energy allocation and life‐history strategies and can be an indicator of nutritional condition. The analysis of an organism's fatty acids is a widely used technique for assessing nutrient and energy transfer, and dietary interactions in food webs. Although there have been many published regional studies that assessed lipid and fatty acid compositions, many only report the mean values of the most abundant fatty acids. There are limited individual records available for wider use in intercomparison or macro‐scale studies. This dataset consists of 4856 records of individual and pooled samples of at least 470 different marine consumer species sampled from tropical, temperate, and polar regions around Australia and in the Southern, Indian, and Pacific Oceans from 1989 to 2018. This includes data for a diverse range of taxa (zooplankton, fish, cephalopods, chondrichthyans, and marine mammals), size ranges (0.02 cm to ~13 m), and that cover a broad range of trophic positions (2.0–4.6). When known, we provide a record of species name, date of sampling, sampling location, body size, relative (%) measurements of tissue‐specific total lipid content and abundant fatty acids, and absolute content (mg 100 g−1 tissue) of eicosapentaenoic acid (EPA, 20:5n3) and docosahexaenoic acid (DHA, 22:6n3) as important long‐chain (≥C20) polyunsaturated omega‐3 fatty acids. These records form a solid basis for comparative studies that will facilitate a broad understanding of the spatial and temporal distribution of marine lipids globally. The dataset also provides reference data for future dietary assessments of marine predators and model assessments of potential impacts of climate change on the availability of marine lipids and fatty acids. There are 480 data records within our data file for which the providers have requested that permission for reuse be granted, with the likely condition that they are included as a coauthor on the reporting of the dataset. Records with this condition are indicated by a "yes" under "Conditions_of_data_use" in Data S1: Marineconsumer_FAdata.csv (see Table 2 in Metadata S1 for more details). For all other data records marked as "No" under "Conditions_of_data_use," there are no copyright restrictions for research and/or teaching purposes. We request that users acknowledge use of the data in publications, research proposals, websites, and other outlets via formal citation of this work and original data sources as applicable. [ABSTRACT FROM AUTHOR]

Information regarding the vagile fish fauna and their use of rare polychaete reefs as habitat or feeding area is almost unheard of in the tropics. Of great interest is whether the construction of such biogenic reefs in an otherwise featureless habitat such as a mudflat increases structural complexity thereby enhancing fish abundance and ecological functioning. The Jeram polychaete reef (Straits of Malacca) is unique and recurrent; on the mudflat, it emerges, grows, and decimates within a year. We tested the hypothesis that the enhanced reef resources (prey) modify the reef ichthyofauna in terms of community structure and trophodynamics. The largely juvenile fish that visited the reef totaled 69 species from a 9-month study. Although sharing 57 common species, the reef fish assemblages had less species and diversity than the mudflat (90 species) and also lower abundance and biomass. Temporal variability in the reef's fish community structure appeared to be tied to the reef dynamics, food availability, and environment. Stable isotope (C and N) results suggest a food web of five trophic levels emanating from phytoplankton and benthic diatoms as basal sources, similar to the mudflat. The enhanced prey resources modified the ichthyofauna, but did not impact reef fish trophodynamics in terms of feeding guild, trophic level, and dietary carbon. Although the polychaete feeding guild was distinct in the reef, most reef fishes as well as mudflat fishes were generalist predators. The reef supports local fisheries, functioning as a feeding and habitat area for 58 fish species of commercial importance. [ABSTRACT FROM AUTHOR]

• There is a debate on the topic of possible ecological equations of state (EESs). • A pro-MaxEnt view (A) proposes developing EESs formally decoupled from physics. • A pro-OBEC view (B) proposes just the contrary. • B reanalyzes even more deeply varied interdisciplinary links. • Physics-like EESs are more reliable, a roadmap for ecological modeling is provided. An interesting dialogue is developed between Newman et al. (2023) and Riera et al. (2023), in which proposals related to the development of equations of state in ecosystem ecology are discussed in depth. This debate is more important than it first appears, since the persistent gap between theoretical and empirical ecology is due, in part, to the absence of a comprehensive paradigm in this field. As it is exemplified in the first section of this article, a sequence of models derived from a reliable equation of state would help to bridge the aforementioned gap. Although this manuscript is analytically monolithic, five main thematic strands can be identified: (i) Examination of the objections of Newman et al. (2023), juxtaposing them with key concepts from ecology, information theory, physics and the MaxEnt algorithm. (ii) Validation of the criteria in (i) through theoretical and data-based examples. (iii) Interdisciplinary linkages between (i) and (ii). (iv) Epistemological generalizations from the previous strands to obtain a strategic roadmap for interdisciplinary modeling in ecology. (v) Conclusions referred to the general meaning of points (i) and (ii). On a general level, our objective is that this manuscript will go beyond a simple academic debate, being useful for colleagues interested in interdisciplinary modeling. [ABSTRACT FROM AUTHOR]

Phthalate esters (PAEs) have received widespread attentions due to their ubiquity in various kinds of matrices and potential biotoxicity. This study systematically compared the concentrations, bioaccumulation, trophodynamics and health risk of PAEs in 25 species (n = 225) collected from a marine (Bohai Bay, BHB) and freshwater environment (Songhua River, SHR), China. Results showed that di-(2-ethylhexyl) phthalate and di-n-butyl phthalate were the predominant PAEs in the organisms from the two aquatic environments. The total concentrations of 6 PAEs in algae and fish from SHR were significantly higher than those from BHB. Two food webs were constructed in BHB and SHR based on the abundance of 15N in the organisms. All the PAEs except dimethyl phthalate exhibited trophic dilution with the trophic magnification factors less than 1. Moreover, an obvious biodilution of PAEs was observed in marine food web compared to freshwater food web. A low health risk of PAEs was found in organisms from both BHB and SHR. However, di-(2-ethylhexyl) phthalate exhibited a potential carcinogenic risk by consumption of some benthos in BHB and fish in SHR. This study provides a valuable perspective for understanding the trophodynamics and health risk of PAEs in marine and freshwater environments. [Display omitted] • Concentrations of 6 PAEs vary greatly among the 25 species. • The values of log K ow are positively correlated with log BAF of PAEs. • Two food webs are constructed based on the values of δ15N in 25 species. • Five PAEs exhibit biodilution in both marine and freshwater food webs. • DEHP may pose a carcinogenic risk by consumption of some benthos and fish. [ABSTRACT FROM AUTHOR]

To appreciate coastal trophodynamics, it is necessary to understand the dynamics and control of the spring and late summer/autumn phytoplankton blooms. Classically mesozooplankton are considered as main players in these blooms. Microzooplankton likely also are important in these dynamics, but their role is poorly understood. Critically, due to their rapid generation times, microzooplankton may exhibit rapid shifts during blooms. Through field sampling and rate measurements (dilution experiments) in a well-studied temperate coastal ecosystem (Helgoland, southern North Sea) we ask if there are differences in the trends exhibited between and within the spring and late summer/autumn blooms. To achieve this, we examined early, mid and late bloom periods in both seasons. We found 1) a shift in trophic composition during both blooms, with a trend from strongly autotrophic mixotrophs (e.g. Mesodinium) to mixotrophs and then towards heterotrophs; 2) an increase in intraguild predation at the end of the blooms; and 3) although microzooplankton were major consumers of the spring bloom (grazing coefficient g: 0.23–0.25 d−1; daily percent loss of production Pp: 36–47%), they were unlikely to control it, while in contrast, microzooplankton appeared to play a major role in controlling the late summer/autumn bloom (grazing coefficient g: 0.14–1.53 d−1; daily percent loss of production Pp: 24–103%). In doing so, we suggest that any simplifications that consider these seasonal blooms to be relatively homogeneous and similar will lead to substantial errors in the assessment of coastal trophodynamics. [ABSTRACT FROM AUTHOR]

The pervasive contamination of novel brominated flame retardants (NBFRs) in remote polar ecosystems has attracted great attention in recent research. However, understanding regarding the trophic transfer behavior of NBFRs in the Arctic and Antarctic marine food webs is limited. In this study, we examined the occurrence and trophodynamics of NBFRs in polar benthic marine sediment and food webs collected from areas around the Chinese Arctic Yellow River Station ( n = 57) and Antarctic Great Wall Station ( n = 94). ∑ 7 NBFR concentrations were in the range of 1.27-7.47 ng/g lipid weight (lw) and 0.09-1.56 ng/g lw in the Arctic and Antarctic marine biota, respectively, among which decabromodiphenyl ethane (DBDPE) was the predominant compound in all sample types. The biota-sediment bioaccumulation factors (g total organic carbon/g lipid) of NBFRs in the Arctic (0.85-3.40) were 4-fold higher than those in the Antarctica (0.13-0.61). Trophic magnification factors (TMFs) and their 95% confidence interval (95% CI) of individual NBFRs ranged from 0.43 (95% CI: 0.32, 0.60) to 1.32 (0.92, 1.89) and from 0.34 (0.24, 0.49) to 0.92 (0.56, 1.51) in the Arctic and Antarctic marine food webs, respectively. The TMFs of most congeners were significantly lower than 1, indicating a trophic dilution potential. This is one of the very few investigations on the trophic transfer of NBFRs in remote Arctic and Antarctic marine ecosystems, which provides a basis for exploring the ecological risks of NBFRs in polar regions.

Individual body size strongly influences the trophic role of marine organisms and the structure and function of marine ecosystems. Quantifying trophic position–individual body size relationships (trophic allometries) underpins the development of size‐structured ecosystem models to predict abundance and the transfer of energy through ecosystems. Trophic allometries are well studied for fishes but remain relatively unexplored for cephalopods.Cephalopods are important components of coastal, oceanic and deep‐sea ecosystems, and they play a key role in the transfer of biomass from low trophic positions to higher predators. It is therefore important to resolve cephalopod trophic allometries to accurately represent them within size‐structured ecosystem models.We assessed the trophic positions of cephalopods in an oceanic pelagic (0–500 m) community (sampled by trawling in a cold‐core eddy in the western Tasman Sea), comprising 22 species from 12 families, using bulk tissue stable isotope analysis and amino acid compound‐specific stable isotope analysis. We assessed whether ontogenetic trophic position shifts were evident at the species‐level and tested for the best predictor of community‐level trophic allometry among body size, taxonomy and functional grouping (informed by fin and mantle morphology).Individuals in this cephalopod community spanned two trophic positions and fell into three functional groups on an activity level gradient: low, medium and high. The relationship between trophic position and ontogeny varied among species, with the most marked differences evident between species from different functional groups. Activity‐level‐based functional group and individual body size are best explained by cephalopod trophic positions (marginal R2 = 0.43).Our results suggest that the morphological traits used to infer activity level, such as fin‐to‐mantle length ratio, fin musculature and mantle musculature are strong predictors of cephalopod trophic allometries. Contrary to established theory, not all cephalopods are voracious predators. Low activity level cephalopods have a distinct feeding mode, with low trophic positions and little‐to‐no ontogenetic increases. Given the important role of cephalopods in marine ecosystems, distinct feeding modes could have important consequences for energy pathways and ecosystem structure and function. These findings will facilitate trait‐based and other model estimates of cephalopod abundance in the changing global ocean. [ABSTRACT FROM AUTHOR]

Biomagnification of metals (Cd, Cr, Cu, Mn, Ni, Zn, Fe) was investigated in 14 species of Caspian Sea commercial fishes using 13C and 15N analyses to decode their trophic position (TP). The stable nitrogen isotope ratios varied among the Caspian Sea fish species from 8.7 to 13.8‰ while the stable carbon isotope ratios varied from −23.7 to −17.6‰. The TPs varied between 2.2 and 4.9. Clupeonella caspia had the lowest average TP, and Acipenseridae species (except Acipenser persicus) and Sander lucioperca had higher average TPs. Wide intra- and inter-specific differences were observed in metal concentrations. The stable isotope results were relatively coordinated with feeding behaviour of species. However, some exceptions were observed particularly in Alburnus chalcoides and S. lucioperca. By comparing logarithmic concentration of metals vs. TPs, no metal biomagnification was observed. The estimated daily intakes of metals were lower than the provisional tolerable daily intakes and, thus, these amounts do not pose any threat on human health. [ABSTRACT FROM AUTHOR]

• Japanese sardine isotope ratios greatly vary geographically and seasonally. • Baseline fluctuation is the primary driver of sardine isotope composition. • Life-stage- and region-dependent fish movements also have significant impacts. • Mechanistic prediction of small pelagic fish isotopes is possible but challenging. Understanding and predicting variability in the stable isotope ratios of nitrogen and carbon (δ 15N and δ 13C, respectively) of small pelagic fish is crucial to enable isotopic studies of a variety of marine predators that feed on them. However, because the isotope ratios reflect plastic feeding habits and fish migration in addition to baseline variation, their predictions require a mechanistic understanding of how each factor contributes. Here, we investigated the habitat-wide variability of δ 15N and δ 13C of the Japanese sardine Sardinops melanostictus in the western North Pacific and its marginal seas (the East China Sea and the Sea of Japan). By combining this with the archived particulate organic matter (POM) dataset as a baseline, we aimed to understand how ecological processes and baseline fluctuations affect isotope ratios of the sardine. Both δ 15N and δ 13C of sardine showed significant geographical and seasonal trends, with higher values in southern nearshore areas, including the Seto Inland Sea, intermediate values in marginal seas and lower values in Pacific offshore areas. As the variations were largely consistent with the geographic trend and the temporally integrated seasonal trend of isotope ratios of POM, respectively, the baseline variations are the main determinant of sardine isotope composition. The trophic positions of sardine are therefore not significantly different between regions, with possible minor increases in the southern nearshore area. Adults showed less geographic variation than larvae and juveniles, likely due to slower turnover periods and wider migration ranges. Although larval and juvenile isotope ratios in marginal seas mostly reflected the local baseline, those in the Pacific offshore often reflected the baseline in the neighbouring southern region, suggesting contrasting juvenile movements between regions. Our results suggest that the δ 15N and δ 13C of Japanese sardine strongly reflect baseline variations, but can also be influenced by life-stage- and region-dependent fish movements, thereby demonstrating both the possibility and difficulty of mechanistically modelling the isoscapes of lower trophic position species. [ABSTRACT FROM AUTHOR]

The article discusses the expansion of the previously formulated approach to modeling aspects of the reproductive cycle, taking into account the changes in the habitat and metamorphosis in the development of fish. Excessive accumulation of nutrients with prolonged use of a reservoir for artificial growth of juveniles or accelerated decomposition of organic nitrogen and phosphorus may in some cases affect the success of the reproductive process. This creates an indirect effect on long-term trends in population dynamics. In some cases, the increase in the influx of organic phosphorus further leads to a state of eutrophication and may affect the insufficient aeration of breeding sites, leading to hypoxia for hatched larvae. Even worsen the situation with the consumption of oxygen in the water at the mass destruction of eggs. Lack of organic matter leads to insufficient development of planktonic organisms for optimal growth of fishes. The system of survivability equations for calculation competing individuals of the generation is supplemented by a functional extension using an iterative model of biogenic elements dynamics, based on the analysis of processes in the ecosystem of Lake Chao. The block of the model for calculating the inflow and destruction of organic matter is synchronized with a continuous-discrete computational structure that takes into account the interrelated changes in mortality factors and the rate of development of juvenile fish during transitions between generalized ecological and physiological stages of development.

This paper examines the structure and dynamics of the marine ecosystem surrounding Haida Gwaii (an archipelago in the southeastern Gulf of Alaska). Based on previous research, a set of improved mass-balanced models was constructed in Ecopath with Ecosim (EwE) to represent ecosystem states existing circa 1900, 1950, and currently. These models feature increased taxonomic and ecological resolution relative to their predecessors across trophic levels and size classes from zooplankton to whales. A more detailed representation of Pacific herring (Clupea pallasii), including its age structure, predators, and prey, was introduced to permit modeling of the ecosystem role of herring as a forage fish, as well as the ecological impacts of herring fisheries. Gross ecosystem structure and herring trophodynamics were compared across ecosystem states using size spectra and ecological indicators, including mixed trophic impacts (MTIs). The 1950 model was fitted to a comprehensive set of biomass and catch time series. Dynamic ecosystem simulations evaluated the influence of fishing, predation, other natural mortality, and primary productivity trends on ecosystem behavior since 1950, as well as the relative importance of top-down versus bottom-up forcing. Size spectra and ecosystem indicators suggest that the Haida Gwaii ecosystem has not undergone a radical structural shift since 1900, despite heavy exploitation of numerous marine mammals and fish. Moreover, MTIs show that herring constitutes an important mid-trophic level node in the food web, participating in complex interactions with many predators, prey, and competitors. Dynamic ecosystem simulations demonstrate that trends in fishing mortality, trophic interactions, and primary productivity (correlated with the Pacific Decadal Oscillation) are all necessary to explain historical Haida Gwaii ecosystem behavior. These interacting drivers yield a mosaic of top-down and bottom-up trophic control for trophic interactions involving herring and throughout the food web. Simulation results also suggest that production of several herring, salmon, and groundfish stocks may have recently become partially decoupled from primary productivity, perhaps due to changes in copepod guild composition. These results also indicate that a biodiversity decline and “fishing down the food web” occurred off Haida Gwaii since 1950. Finally, the fitted 1950 model provides a robust platform for dynamic ecosystem simulations.

The ubiquitous presence of pharmaceuticals and personal care products (PPCPs) in environments has aroused global concerns; however, minimal information is available regarding their multimedia distribution, bioaccumulation, and trophic transfer in marine environments. Herein, we analyzed 77 representative PPCPs in samples of surface and bottom seawater, surface sediments, and benthic biota from the Bohai Sea. PPCPs were pervasively detected in seawater, sediments, and benthic biota, with antioxidants being the most abundant PPCPs. PPCP concentrations positively correlated between the surface and bottom water with a decreasing trend from the coast to the central oceans. Higher PPCP concentrations in sediment were found in the Yellow River estuary, and the variations in the physicochemical properties of PPCPs and sediment produced a different distribution pattern of PPCPs in sediment from seawater. The log D ow , showed a linear and positive relationship with bioaccumulation and trophic magnification factors and a parabolic relationship with biota-sediment accumulation factors. The trophodynamics of miconazole and acetophenone are reported for the first time. This study provides novel insights into the multimedia distribution and biomagnification potential of PPCPs and suggests that log K ow , showed a linear and positive relationship with bioaccumulation and trophic magnification factors and a parabolic relationship with biota-sediment accumulation factors. The trophodynamics of miconazole and acetophenone are reported for the first time. This study provides novel insights into the multimedia distribution and biomagnification potential of PPCPs and suggests that log D ow is a better indicator of their bioaccumulation and trophic magnification.

The distributional ranges of Cape anchovy Engraulis encrasicolus and Natal anchovy Stolephorus holodon presently overlap at their eastern and western extremes, respectively, off South Africa's east coast. These species might become more strongly sympatric as a consequence of changed distributions caused by climate change, possibly leading to intensified interspecific competition for trophic and other resources. A comparative analysis of the trophodynamics of the two species, which set out to assess elements of current niche partitioning between them, was conducted through morphological, dietary and stable-isotope analyses of specimens caught off South Africa's east coast. Cape anchovy have larger gillraker spacing, gain the majority of their dietary carbon from large (>3 000 µm total length) planktonic crustaceans and occupy a higher trophic level than Natal anchovy, which have smaller gillraker spacing and gain the majority of their dietary carbon from planktonic crustaceans of two size classes (900–1 400 µm and 2 800–3 200 µm total length). These results indicate an element of trophic partitioning between the two species that will mitigate against interspecific competition. [ABSTRACT FROM AUTHOR]

Coral reef food webs are complex, vary spatially and remain poorly understood. Certain large predators, notably sharks, are subsidized by pelagic production on outer reef slopes, but how widespread this dependence is across all teleost fishery target species and within atolls is unclear.North Malé Atoll (Maldives) includes oceanic barrier as well as lagoonal reefs. Nine fishery target predators constituting ca. 55% of the local fishery target species biomass at assumed trophic levels 3–5 were selected for analysis. Data were derived from carbon (δ13C), nitrogen (δ15N) and sulphur (δ34S) stable isotopes from predator white dorsal muscle samples, and primary consumer species representing production source end‐members.Three‐source Bayesian stable isotope mixing models showed that uptake of pelagic production extends throughout the atoll, with predatory fishes showing equal planktonic reliance between inner and outer edge reefs. Median plankton contribution was 65%–80% for all groupers and 68%–88% for an emperor, a jack and snappers.Lagoonal and atoll edge predators are equally at risk from anthropogenic and climate‐induced changes, which may impact the linkages they construct, highlighting the need for management plans that transcend the boundaries of this threatened ecosystem. [ABSTRACT FROM AUTHOR]

The dual function of fatty acids as both biomarkers of phytoplankton community structure and proxies of their nutritional value is becoming increasingly recognized as a substantial complement to elemental stoichiometry studies in aquatic ecology and aquaculture. Despite information on fatty acid composition of marine microalgae being more abundant, phytoplankton fatty acid reviews as well as information on their nutritional quality and effects in food webs are far more frequent for freshwater species. Here, 683 fatty acid profiles of 115 genera of marine microalgae belonging to 17 classes from eight phyla and cultured under nonstressful conditions were compiled. Data analysis allowed establishment of fatty acid reference values that can be used to quantitatively determine marine phytoplankton community structure with an unprecedented descriptive level. Fatty acids also served to generate the first microalgae nutritional index adapted to requirements of consumers and their trophic upgrading capabilities. Fatty acid profile allowed taxonomically differentiating among marine microalgae within a group comprising 14 classes and the Bacillariophyta phylum. Phylogeny was the strongest driving force of fatty acid variation, whereas the marine or freshwater origin of microalgae contributed <1%. Nutritionally, marine microalgae were more homogeneously arranged at the phylum level, with the Dinophyta separately scoring the maximum nutritional value. The phylum Chlorophyta comprised strictly marine classes and other classes also present in freshwaters and showed the highest within‐phylum nutritional quality variability. Such variability is relevant and recommends using specific taxonomic terminology for green lineage microalgae regarding their nutritional value. [ABSTRACT FROM AUTHOR]

[Display omitted] • Terrestrial C 3 plants in the ATTZ were the main supporter of aquatic consumers all year round. • Seasonal and interannual WLF driven by Three Gorges Project and HC restricted autochthonous production. • Higher TPs and longer food chains were shown during the dry than the wet season. • Resource diversity and habitat complexity reduced the strength of trophic interactions. • HC and natural WLFs are crucial in maintaining ecosystem stability of large floodplain lakes. Variation in hydrological connectivity (HC) between rivers and lakes gives rise to periodic large water level fluctuation (WLF) in river-connected lakes (RCL). However, how WLF shapes the material cycling and concomitant trophodynamics of RCL remain unclear. Here we evaluated the resource availability, relative contributions of autochthonous and allochthonous carbon sources (by Bayesian mixing models) and trophic structure (using δ13C and δ15N) of Lake Poyang, the largest freshwater lake in China, during different hydrological periods. Terrestrial C 3 plants in the aquatic/terrestrial transition zones (ATTZ) were the main supporter of aquatic consumers all year round. Compared with historical data, the contributions of autochthonous production to aquatic food webs were low. This is primarily ascribed to the influences of hydrological regimes in that the operation of Three Gorges Dam and HC changed the rhythm of WLF in Lake Poyang, restricting the production of aquatic vegetation and epiphytic algae. Most common fish species indicated higher trophic positions (TPs) during the dry than wet season, but only eleven of thirty-six common species showed a statistically significant increase (p < 0.05). Our study reveals a relatively consistent trophic diversity of consumer communities (fish and aquatic invertebrates) during dry and wet seasons, but each trophic guild showed specific trophic response to WLF, as they flexibly adjusted feeding strategies and the degree of trophic niche differentiation. Although WLF triggered fluctuations in the resource availability and species composition of lake food webs, and the TPs and trophic niches of aquatic consumers during different hydrological periods, the resource diversity and habitat complexity driven by HC and WLF reduced the strength of trophic interactions, and thus resulted in overall stability of food web trophodynamics and trophic structure of Lake Poyang. Our findings highlighted the importance of HC and natural WLFs in maintaining the ecosystem stability of large floodplain lakes, and that seasonal WLF patterns should be maintained in future floodplain lake management to conserve biodiversity and the resilience of ecological functions. [ABSTRACT FROM AUTHOR]

The increased frequency of publications concerning trophic ecology of coral reefs suggests a degree of interest in the role species and functional groups play in energy flow within these systems. Coral reef ecosystems are particularly complex, however, and assignment of trophic positions requires precise knowledge of mechanisms driving food webs and population dynamics. Competent analytical tools and empirical analysis are integral to defining ecosystem processes and avoiding misinterpretation of results. Here we examine the contribution of trophodynamics to informing ecological roles and understanding of coral reef ecology. Applied trophic studies of coral reefs were used to identify recent trends in methodology and analysis. Although research is increasing, clear definitions and scaling of studies is lacking. Trophodynamic studies will require more precise spatial and temporal data collection and analysis using multiple methods to fully explore the complex interactions within coral reef ecosystems.

Flow of essential fatty acids (EFAs) through food webs is critical for the health of individual animals, populations, and communities. Planktonic eggs may play a central role in marine systems because they are highly concentrated in EFAs, superabundant, and consumed by a variety of species. Previous research suggests that egg fatty acid composition should not be useful for trophodynamic studies because it should be tightly regulated to meet the nutritional needs of embryos. Eight years of sampling the egg boon of the teleost fish red drum (Sciaenops ocellatus) provided the opportunity to test the hypothesis that extreme climatic events differentially alter abundances of prey populations and, ultimately, egg fatty acid composition. Fatty acid composition of eggs varied significantly among years and three major patterns of interannual variation (principal components) paralleled trends in the Palmer Drought Severity Index. Each of the first three principal components was related to abundances of particular prey (blue crabs, filter‐feeding fishes, and brown shrimp, respectively) during the spring and summer. Summer abundances of blue crab and brown shrimp were most strongly correlated with bay salinity 12–14 months earlier. Summer abundances of filter‐feeding fishes were most strongly correlated with bay salinity 0–1 month earlier. The delayed responses of crustacean abundances to variations in bay salinity likely operate through variability in recruitment. The fast connection for filter‐feeding fishes suggests a behavioral response to changing environmental conditions. The analyses revealed changes in trophodynamic flow that were associated with the phases of the climatic event. EFA content of eggs increased during drought years then decreased in the recovery years, indicating the potential for downstream effects on reproductive output, offspring viability, and tissue composition of egg consumers. Generally, nutrients move from intermediate sized consumers to a larger, higher order consumer (adult red drum). Then, trophic flow reverses when the egg boon is exploited by smaller planktivores. The analysis also revealed climate‐related shifts in the degree of benthic‐pelagic coupling and pelagic recycling that were mediated by the egg boons. This study demonstrates that egg boons can be a useful subject for investigations of trophodynamics in marine ecosystems. [ABSTRACT FROM AUTHOR]

Aim: We examined potential environmental drivers of broad‐scale spatial patterns in the trophic structure of marine ecosystems as represented by nitrogen stable isotopes in globally distributed marine predators. Additionally, we assessed the effects of spatial scale on the predictive capabilities of environmental variables. Location: Global oceans. Time period: 2000 to 2015. Major taxa studied: Tunas: Thunnus albacares, Thunnus obesus, Thunnus alalunga. Methods: We undertook a global compilation and meta‐analysis of the bulk nitrogen stable isotope ratios (δ15N values) of three tuna species (n = 4,281). After adjusting for regional variations in baseline δ15N values using a global ocean biogeochemistry model, generalized additive mixed models were employed to infer global‐scale oceanographic controls of trophic structure, using cosmopolitan tuna species as a model. Results: For the three tuna species, variation in trophic position estimated using bulk δ15N values was largely explained by geographical location and the corresponding oxygen minimum layer depth. Tuna trophic positions declined in areas with reduced oxygen at depth. Food‐chain length, as captured by maximum trophic position, was longer in areas of the western Pacific Ocean and shorter in the northern Atlantic and eastern Pacific Oceans. Trophic adaptability of the tuna predators, as indicated by intraspecific variability, was highest in the western and central Pacific Ocean and lowest in the northern Atlantic Ocean. Our analysis demonstrated that while tunas share similar functional trophic roles, deeper‐foraging tuna species had higher trophic positions globally. The predictive capacity of environmental variables decreased at finer (regional) spatial scales. Main conclusions: Our work suggests that habitat compression resulting from the predicted global expansion of oxygen minimum zones with ocean warming will impact the trophic structure of marine food webs and the corresponding foraging habits of marine predators. Spatial scale analyses highlighted the importance of representing differences in regional ecological dynamics in global‐scale trophic and ecosystem models. [ABSTRACT FROM AUTHOR]

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 reef at Lizard Island, Australia. Low, ambient and high sediment loads were maintained on turf-covered coral tiles, with and without grazer exclusion cages, for 1 month. Subsequently, algal turfs were removed and analysed for organic carbon and nitrogen content. Under grazer exclusion, sediment additions decreased algal turf biomass by approximately 63%, while algal turf biomass was the highest on tiles with sediments removed. In the presence of grazing fishes, algal turfs in all treatments were cropped by grazers to similar low biomass levels. Nitrogen content of algal turfs followed a similar trend. Effectively, added sediments decreased the potential yield of algal turf biomass and nitrogen to grazing fishes by an average of 2000 and 3300%, respectively. Sediments profoundly affect algal turf yield to grazing herbivorous fishes and, therefore, the productivity of algal turf-based food chains, potentially diminishing reef-based fisheries. [ABSTRACT FROM AUTHOR]

Small pelagic fishes represent a critical link between zooplankton and large predators. Yet, the taxonomic resolution of the diets of these important fishes is often limited, especially in the Northwest Atlantic. We examined the diets, along with stable isotope signatures, of five dominant small pelagic species of the northeast US continental shelf ecosystem (Atlantic mackerel Scomber scombrus , Atlantic herring Clupea harengus , alewife Alosa pseudoharengus , blueback herring Alosa aestivalis , and Atlantic butterfish Peprilus triacanthus ). Diet analyses revealed strong seasonal differences in most species. Small pelagic fishes predominantly consumed Calanus copepods, small copepod genera ( Pseudocalanus/Paracalanus/Clausocalanus ), and Centropages copepods in the spring, with appendicularians also important by number for most species. Krill, primarily Meganyctiphanes norvegica , and hyperiid amphipods of the genera Hyperia and Parathemisto were common in the stomach contents of four of the five species in the fall, with hyperiids common in the stomach contents of butterfish in both seasons and krill common in the stomach contents of alewife in both seasons. Depth and region were also found to be sources of variability in the diets of Atlantic mackerel, Atlantic herring, and alewife (region but not depth) with krill being more often in the diet of alewife in more northerly locations, primarily the Gulf of Maine. Stable isotope data corroborate the seasonal differences in diet but overlap of isotopic niche space contrasts that of dietary overlap, highlighting the differences in the two methods. Overall, the seasonal variability and consumer-specific diets of small pelagic fishes are important for understanding how changes in the zooplankton community could influence higher trophic levels. [ABSTRACT FROM AUTHOR]

Trophodynamics and chiral signatures of organochlorine pesticides (OCPs), including dichlorodiphenyltrichloroethanes (DDTs), hexachlorocyclohexanes (HCHs), and chlordanes in a food web from Zhoushan Fishing Ground, China, were studied. Residues of OCPs in all teleost fishes were within food safety levels. Strong positive correlations were found between trophic levels (TLs) and wet weight concentrations of target chemicals, with trophic magnification factors (TMFs) from 4.17 to 9.77. Lipid contents and TLs significantly correlated, which indirectly affect the bioaccumulation processes of OCPs. The consistently racemic EF values of α- HCH, as well as invariability of the relative proportions of HCH isomers in different marine species implied that HCHs in animals originate directly from the surrounding environment. However, in vivo biotransformation and/or elimination of o,p ′-DDT cannot be precluded. TMFs of the individual enantiomers further suggest that the influence of achiral biotransformation is too minor to induce enantioselective biomagnification of chiral OCPs through the studied food web. [ABSTRACT FROM AUTHOR]