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Context: Wild fish is a good source of minerals and other high-quality nutrition; however, many wild fish species potentially accumulate hazardous metals, making them a threat to human health. Aims: The aim was to study characteristics and the source of metals in wild fish in the South China Sea by using, for the first time, the correlation of trace metals and stable isotopes. Methods: Analytical instruments and statistical methods were respectively used to determine elements and the relative correlations. Key results: Lead (Pb) and manganese (Mn) tended to accumulate in bluespot mullet and Macao tonguesole. Variation among fish species and spatial differences might be two important factors influencing both the metal concentrations and the selenium (Se):mercury (Hg) molar ratios in biota. Hg, Mn, Pb and tin (Sn) tended to be biomagnified with an increasing trophic level, whereas chromium (Cr) and copper (Cu) showed a trend of biodilution. Conclusions: The Se:Hg molar ratios exhibited noticeable species and spatial variation for the wild fish, whereas the main sources of Sn and Pb contamination might be antifouling reagents and surface applications. Implications: The speciation of the elements is worth investigating next, so as to obtain valuable insight into the state of the wild environment and the impacts to human wellbeing. In this study, significant biomagnification was shown for Hg, Mn, Pb and Sn in the fish food chain. Noticeable dilution was demonstrated for Cu and Cr. Unapparent trend of both biomagnification and biodilution was found for As, Se and Zn. The Se:Hg molar ratios exhibited noticeable species and spatial variation for the wild fish, whereas the antifouling reagent and surface applications might be the main sources of Sn and Pb contamination in fish. [ABSTRACT FROM AUTHOR]

The Cheadle Center at UCSB manages the North Campus Open Space (NCOS), which is a project that has restored 136 acres of upland and wetland habitats that existed before the area was converted into the Ocean Meadows Golf Course in the 1960s. The NCOS restoration project began in 2017 with a fine-scale grading of the site in order to recreate the salt marsh and use the excavated soil to rebuild the upland habitats to the southwest, which are now called the NCOS Mesa. In addition to re-establishing native biodiversity, a key goal of the restoration is to utilize the site as an educational, scientific, and recreational resource. This archived version of the November 2020 newsletter includes updates on a planned new parking lot and outdoor classroom, and brief highlights from the experiences of student workers at NCOS during the pandemic. The feature story focuses on rodent and reptile monitoring with Sherman traps and coverboards. Community photos include Cooper’s Hawk (Accipiter cooperii), tropical kingbird (Tyrannus melancholicus), California Towhee (Melozone crissalis), White-crowned Sparrow (Zonotrichia leucophrys), and a mouse nest.

The relative roles of top-down (consumer-driven) and bottom-up (resource-driven) forcing in exploited marine ecosystems have been much debated. Examples from a variety of marine systems of exploitation-induced, top-down trophic forcing have led to a general view that human-induced predator perturbations can disrupt entire marine food webs, yet other studies that have found no such evidence provide a counterpoint. Though evidence continues to emerge, an unresolved debate exists regarding both the relative roles of top-down versus bottom-up forcing and the capacity of human exploitation to instigate top-down, community-level effects. Using time-series data for 104 reef communities spanning tropical to temperate Australia from 1992 to 2013, we aimed to quantify relationships among long-term trophic group population density trends, latitude, and exploitation status over a continental-scale biogeographic range. Specifically, we amalgamated two long-term monitoring databases of marine community dynamics to test for significant positive or negative trends in density of each of three key trophic levels (predators, herbivores, and algae) across the entire time series at each of the 104 locations. We found that trophic control tended toward bottom-up driven in tropical systems and top-down driven in temperate systems. Further, alternating long-term population trends across multiple trophic levels (a method of identifying trophic cascades), presumably due to top-down trophic forcing, occurred in roughly fifteen percent of locations where the prerequisite significant predator trends occurred. Such alternating trophic trends were significantly more likely to occur at locations with increasing predator densities over time. Within these locations, we found a marked latitudinal gradient in the prevalence of long-term, alternating trophic group trends, from rare in the tropics (

Abstract Food webs are the physical foundations of ecosystems. Visualisations help to find and present structural patterns of these weighted networks and are essential in research, conservation practice and education. There has been no open‐source library drawing weighted food webs with fractional trophic levels clearly. The existing approaches are scattered across separate libraries and programming languages. We provide an ensemble of mutually complementary visualisation methods that enable a general overview of the system, as well as a clear presentation of its details: https://github.com/ibs‐pan/foodwebviz. We use colours, sizes, positions, zoom and movement for precise identification of flows, their magnitudes and connectivity patterns. Vertical positions of nodes highlight the fractional trophic level as the most significant structural variable in a food web. The visualisations are in the form of modular and extensible python functions. Jupyter notebooks display them interactively in HTML. A heat map of food web flows or diet proportions shows their general pattern at a glance while retaining their precise identification. An interactive graph allows tracing the flow of matter over subsequent links. The user can select nodes, zoom, adjust layout parameters and manually drag‐and‐drop nodes. An intuitive animation of particles moving between the nodes uses colours and time dimension to trace connections better. It shows the multivariate food web aspects in one graph, together with a structural indicator, the trophic level. A bar plot and a heat map summarise exchanges of matter between the trophic levels. We bring several complementary and customisable methods together to facilitate accompanying every food web publication and analysis with its visualisation. Users can tinker with the interactive output and method parameters to reach the desired effect. Aesthetically appealing images presenting empirical data help to communicate the importance of species interconnectedness and ecosystem complexity to the broader public. Visualisation tools facilitate incorporating real‐world examples in education.

● Agricultural intensification reduced the complexity and connectance of soil food webs. ● Agricultural intensification impaired the robustness of pollination networks. ● High connectance in co-occurrence networks indicates efficient nutrient utilization. Complex network theory has been increasingly used in various research areas, including agroecosystems. This paper summarizes the basic concepts and approaches commonly used in complex network theory, and then reviews recent studies on the applications in agroecosystems of three types of common ecological networks, i.e., food webs, pollination networks and microbial co-occurrence networks. In general, agricultural intensification is considered to be a key driver of the change of agroecosystems. It causes the simplification of landscape, leads to the loss of biocontrol through cascading effect in food webs, and also reduces the complexity and connectance of soil food webs. For pollination networks, agricultural intensification impaired the robustness by reducing specialization and enhancing generality. The microbial co-occurrence networks with high connectance and low modularity generally corresponded to high efficiency in utilization of nutrients, and high resistance to crop pathogens. This review aims to show the readers the advances of ecological networks in agroecosystems and inspire the researchers to conduct their studies in a new network perspective.

The analysis of food web structures has increased the understanding of the dynamics of organisms belonging to different trophic levels. In this study, the diet of two native species, Glossogobius callidus and Gilchristella aestuaria, was assessed in the presence of two non‐native species, Oreochromis mossambicus and Gambusia affinis, in irrigation ponds, Eastern Cape Province, South Africa. The proportion of dietary items consumed and assimilated by the four fish species were inferred from gut contents and carbon and nitrogen stable isotope analysis. Stable isotope analysis revealed that both G. affinis and O. mossambicus had a larger isotopic niche size than G. callidus and G. aestuaria. Although G. callidus fed on benthic resources and G. aestuaria fed on phytoplankton, gut content analysis showed that G. callidus, O. mossambicus and G. affinis fed predominantly on benthic resources, whereas G. aestuaria fed mainly on plankton resources. Considerable niche overlap corroborates the view that resource competition is a major factor shaping the composition of the four fish species. This study highlighted the low diversity of the food web within the Sundays River Valley irrigation ponds, where food items are shared by all the small‐bodied fishes. [ABSTRACT FROM AUTHOR]

Intertidal habitats (i.e. marine habitats that are (partially) exposed during low tide) have traditionally been studied from a shorebird‐centred perspective. We show that these habitats are accessible and important to marine predators such as elasmobranchs (i.e. sharks and rays). Our synthesis shows that at least 43 shark and 45 ray species, of which 54.5% are currently threatened, use intertidal habitats. Elasmobranchs use intertidal habitats mostly for feeding and as refugia, but also for parturition and thermoregulation. However, the motivation of intertidal habitat use remains unclear due to limitations to observe elasmobranch behaviour in these dynamic habitats. We argue that elasmobranch predators can play an important role in intertidal food webs by feeding on shared resources during high tide (i.e. 'high‐tide predators'), which are accessible and also consumed by terrestrial or avian predators during low tide (i.e. 'low‐tide predators'). In addition, elasmobranchs are able to change the bio‐geomorphology of intertidal habitats by increasing habitat heterogeneity due to feeding activities and may also alter resource availability for other consumers. We discuss how the ecological role of elasmobranchs in intertidal habitats is being affected by the continued overexploitation of these species, and conversely, how the global loss of intertidal areas poses an additional threat to an already vulnerable taxonomic group. We conclude that studies on intertidal ecology should include both low‐tide (e.g. shorebirds) and high‐tide (e.g. elasmobranchs) predatory guilds and their ecological interactions. The global loss of elasmobranch predatory species and intertidal habitat provides additional compelling arguments for the conservation of these areas. [ABSTRACT FROM AUTHOR]

Intraguild predation (IGP) is common in natural and human‐managed systems and plays a critical role in food web dynamics. Although studies have documented the occurrence of IGP across a wide range of predator taxa, quantitative understanding regarding the degree/intensity of IGP remains lacking. I propose an experimental framework combining controlled feeding trials and stable isotope analysis to quantify the degree of IGP in an omnivorous food web in the field consisting of a top predator, a mesopredator, and a shared prey. The degree of IGP is defined as the proportion (in number) of mesopredators consumed in the total diet (shared prey + mesopredator) of top predators. Feeding trials along with stable isotope analysis are used to construct a standard curve of the relationship between the diet composition of top predator and its nitrogen isotope signatures. The nitrogen isotope signatures of field‐collected top predator individuals are then analyzed and interpolated to the standard curve to estimate the degree of IGP in the field. The proposed framework leverages the strengths of different experimental approaches to study trophic interactions, providing a practical tool for quantifying IGP in a more accurate (controlled feeding trials and standard IGP curve) and realistic (stable isotope analysis of field samples) fashion. The current framework can be further extended to food webs involving more complex interactions (e.g., multiple shared prey) and complemented with other approaches (e.g., molecular gut content analysis) to capture a more complete picture of IGP dynamics in the field. [ABSTRACT FROM AUTHOR]

Popular as aquarium fish, armored catfishes from South America (Pterygoplichthys spp.) have been introduced and become invasive in tropical and subtropical regions worldwide. These ecosystem engineers can deplete basal resources (e.g., periphyton and detritus), with potential negative effects for native fauna. We studied the trophic ecology of fishes in the Usumacinta River Basin, Guatemala, where Pterygoplichthys is now widespread and locally abundant. We analyzed stable isotopes (δ13C, δ15N) in fish tissues and basal resources to assess the potential impact of Pterygoplichthys on the trophic ecology of six co‐occurring native fishes that feed at a similar trophic level (Astyanax aeneus, Dorosoma petenense, Thorichthys pasionis, Oscura heterospila, Poecilia mexicana, and Gambusia sexradiata). The study was conducted during the dry season in the La Pasion (LPR; high invasion) and San Pedro (SPR; low invasion) rivers. We compared isotopic spaces occupied by native fish and Pterygoplichthys, estimated isotopic overlap, and evaluated the trophic displacement of native species. We also evaluated the relationships of environmental factors, including the relative biomass of the invasive catfish, with δ13C and δ15N signatures. Except for P. mexicana, native species had lower isotopic overlap with the catfish in LPR. Native fish isotopic spaces were compressed and shifted toward higher trophic positions in LPR relative to SPR. Benthic food resources were important for Pterygoplichthys in both rivers, and water‐column resources had greater relative importance (RI) for native species in LPR. Native fish δ13C was significantly associated with Pterygoplichthys biomass, conductivity, and water flow velocity; and water depth and sedimentation had a significant association with native fish δ15N. Findings provide evidence that invasive Pterygoplichthys, along with environmental factors, impact the trophic ecology of native fish in the Usumacinta Basin. Additional field research conducted over longer time periods and mesocosm experiments that account for fish assemblage and environmental variation could elucidate Pterygoplichthys impacts via food resource depletion or habitat alteration. [ABSTRACT FROM AUTHOR]

Eurasian red squirrels Sciurus vulgaris have unusually high δ13C values compared to other forest rodents, which is seemingly related to the consumption of 13C-enriched conifer seeds. To test this hypothesis, we analyzed the hair of wild and zoo-kept red squirrels, seeds of pine and spruce, and feathers of specialized and opportunistic consumers of conifer seeds, crossbills Loxia spp., and woodpeckers Dendrocopos major. Data on the isotopic composition (δ13C and δ15N values) of hair or feathers of other species of forest rodents and birds were obtained from published studies. The range of mean δ13C values of hair of wild forest rodents (19 species) exceeded 10 ‰. All squirrel species had high 13C content, S. vulgaris having maximum δ13C values. In contrast, S. vulgaris kept in captivity had an isotopic composition similar to other captive rodents. The feathers of crossbills were enriched in 13C compared to other forest birds (15 species), while seeds of coniferous trees often had higher δ13C values compared to seeds of other woody plants. Distinctiveness of the isotopic composition of mammals and birds feeding on the seeds of coniferous trees suggests that this resource can be traced through the entire forest food web. [ABSTRACT FROM AUTHOR]

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Remnant oyster reefs support diverse communities of invertebrates and fish, and there is growing interest in restoring this important habitat. Whether the construction of new oyster reefs will enhance or simply redistribute existing fisheries' productivity depends on their trophic role–which, to date, is unknown for Australian estuaries. In this study, conducted in Port Stephens, Australia, stable isotope analysis was used to determine trophic linkages among remnant oyster reefs and their resident and transient species. Specifically, this study elucidated whether the potential trophic linkages could be arising through the direct consumption of reef-forming bivalves or from the uptake of oyster-generated organic matter found in the sediment and consumption of reef-dwelling organisms. A total of six primary producers and 35 consumers of distinct feeding guilds were sampled. Results indicated oyster reefs are contributing to the trophic ecology of both resident and transient species, both through direct predation on the reef bivalves but also indirectly through consumption of the reef benthic organic matter and consumption of other reef-dwelling organisms. Oysters and mussels were an important prey group (> 40% contribution) for three resident and five transient species, including polychaetes, blue swimmer crabs, toadfish, luderick, leatherjackets, oyster gobies, and stingarees. Benthic organic matter from the oyster reef was found to be a primary resource for 12 residents and four transient species, including crabs, shrimps, gastropods, and fish. Oyster reefs are key foraging grounds in the estuarine seascape, and their restoration will enhance fisheries productivity by broadening the trophic resource base and contribute to the estuarine energy transfer to higher trophic levels. [ABSTRACT FROM AUTHOR]

Birds' nests hold rich and diverse communities of invertebrates with complex interspecific interactions whose study could improve our understanding of food webs and resource dynamics. To reach this goal, identification of the participants of such interactions is basic but current knowledge on some key groups such as hymenopteran parasitoids is admittedly poor and unreliable. Here we describe the invertebrate fauna in nests of the Eurasian wryneck Jynx torquilla Linnaeus, 1758 (Piciformes: Picidae) and the relative importance of various trophic guilds. We found a rich community where ectoparasitic Diptera of birds, parasitoid wasps and scavenger Diptera had a prominent representation. We specifically studied the natural enemies of the most abundant bird ectoparasite Carnus hemapterus Nitzsch, 1818 (Diptera: Carnidae), which revealed that Kleidotoma caledonica Cameron, 1888 (Hymenoptera: Figitidae) is a specialized and frequent parasitoid of the ectoparasite. Information on the association between other parasitoid wasps, parasitoid flies and their hosts is also off ered. Such associations could result in trophic cascades with remarkable consequences for the avian host. [ABSTRACT FROM AUTHOR]

The food and feeding links and sources in an impacted tropical estuary situated along India's western coast, the Ulhas River Estuary (URE) was analyzed employing the stable carbon and nitrogen isotopic signatures (δ13C and δ15N). Three basal carbon sources, such as mangrove leaves, particulate organic matter (phytoplankton), and detritus, were analyzed together with eight consumer groups from various trophic guilds. The δ13C varied from − 19.67 to − 24.61‰, whereas δ15N ranged from 6.31 to 15.39‰ from the primary consumer to the top predator species. The stable isotope mixing model developed for URE revealed a phytoplankton based pelagic food chain and detritus based benthic food chain in URE. The fairly larger value of SEA (Standard Ellipse Area) in the URE suggest a much broader food web structure and high trophic diversity in the ecosystem. Higher influence of detritus on the assimilated diet of majority of consumers and evidences of nitrogen enrichment in the basal sources such as detritus and particulate organic matter by anthropogenic activities in URE point towards nitrogen pollution and subsequent trophic disturbance in this tropical estuarine ecosystem. [ABSTRACT FROM AUTHOR]

Managing eutrophied systems using only nutrient decreases to impose bottom–up control can be economically and ecologically challenging. Top–down controls through increased consumption have sometimes effectively controlled phytoplankton blooms. However, mechanistic insights, especially on possible trophic cascades, are less understood in brackish, species‐poor coastal waters, where large cladocera are absent. In this study, we set‐up large mesocosms for three consecutive years during the growing season. One set of mesocosms contained mesopredators (gobies and shrimps), whereas the other mesocosms had no such mesopredator present. The results were standardized to monitoring data from the ecosystem to track possible differences between treatments and the system. We found that mesopredator mesocosms showed lower turbidity, phytoplankton biomass and nutrients compared to no‐mesopredator mesocosms, and compared to the ecosystem. This decrease allowed macrophytes to colonize water depths only sparsely colonized in the ecosystem. Rotifer biomass increased in mesopredator mesocosms compared to the ecosystem and to the no‐mesopredator mesocosms. Likewise, copepod biomass that potentially grazes upon rotifers and other microzooplankton decreased in mesopredator mesocosms. No‐mesopredator mesocosms were colonized by an omnivorous mesograzer Gammarus tigrinus, potentially creating additional pressure on macrophytes and increasing grazing‐mediated nutrient release. Zooplankton was not able to control the non‐nutrient limited phytoplankton. We propose a new mechanism, where a higher mesopredator density will increase grazing on phytoplankton by promoting microzooplankton capable of grazing on picophytoplankton. This proposed mechanism would contrast with freshwater systems, where a decrease of zooplanktivorous fish would promote larger phytoplankton grazer like cladocera. Biomanipulation in such species‐poor eutrophic coastal waters may be more successful, due to less trophic pathways, that can cause complex top–down controls like in other systems. Stocking eutrophic coastal waters with gobies and shrimps may be an alternative biomanipulative approach rather than selectively removing large piscivorous or omnivorous fish from eutrophic coastal waters. [ABSTRACT FROM AUTHOR]

Fire is a common disturbance in many biomes, with both beneficial and detrimental effects on soil biology, which largely depend on fire intensity. However, little is known about the impact of fire on soil nematode communities in terrestrial ecosystem. In the present study, we investigated the effects of short‐term prescribed fire on soil nematode communities and soil properties in an old‐field grassland in Northern China. The results showed that burning significantly increased soil nematode abundance by 77% and genus richness by 49% compared to the control. Burning also decreased taxon dominance by 45% (Simpson's D) and increased nematode diversity by 31% (Shannon‐Weaver H'). However, burning increased plant parasites (particularly genera Cephalenchus and Pratylenchus) and shifted community to more bacterial‐feeding genera (i.e., decreased Channel Index). Generally, burning increased soil bio‐available nitrogen (NH4+–N and NO3−–N) content, which would be the main drivers causing nematode community to flourish via a "bottom‐up" effect. These results suggest that prescribed fire increases nematode diversity and alters community composition toward more plant parasites and bacterial feeders. Our findings highlight the importance of prescribed fire management in shaping short‐term nematode community structure and function, but the long‐term effects and impacts of these changes on soil nutrient and carbon cycling remain unknown. [ABSTRACT FROM AUTHOR]

Hokkaido Island is inhabited by two salamander species, Siberian salamander (Salamandrella keyserlingii) and Ezo salamander (Hynobius retardatus), which were previously considered incompatible to cohabit due to the predation and/or competition between them. Both species had never been seen reproducing sympatrically until a recent discovery in a pond where the two species spawn concurrently. We investigated their potential interspecific interaction, by identifying the trophic niche of the coexisting populations in this pond using isotope analysis. We initially conducted aquarium experiments to determine the trophic discrimination factor (TDF) of main-body δ values, which are required to accurately interpret the isotope ratios in the field. The TDF of δ15N and δ13C were 1.6‰ and 0.1‰ for S. keyserlingii and 1.5‰ and 0.5‰ for H. retardatus, respectively. The δ15N and δ13C results from the pond in June suggested the possibility that H. retardatus larva may prey on S. keyserlingii larva, but this prey–predator interaction had subsided by July, if ever. Further, the interspecific variations in δ values suggested that the two species consumed different foods in July, when both species reached isotopic steady states. Thus, we conclude that the coexisting salamander larvae do not have continuous prey–predator or competitive interaction as expected from their exclusive distribution patterns. The unsustainable negative interspecificity may be avoided due to microhabitat segregation in the pond or by a decrease in the S. keyserlingii population density after predation. [ABSTRACT FROM AUTHOR]

Mercury (Hg) is a serious concern for aquatic ecosystems because it may biomagnify to harmful concentrations within food webs and consequently end up in humans that eat fish. However, the trophic transfer of mercury through the aquatic food web may be impacted by several factors related to network complexity and the ecology of the species present. The present study addresses the interplay between trophic ecology and mercury contamination in the fish communities of two lakes in a pollution‐impacted subarctic watercourse, exploring the role of both horizontal (feeding habitat) and vertical (trophic position) food web characteristics as drivers for the Hg contamination in fish. The lakes are located in the upper and lower parts of the watercourse, with the lower site located closer to, and downstream from, the main pollution source. The lakes have complex fish communities dominated by coregonids (polymorphic whitefish and invasive vendace) and several piscivorous species. Analyses of habitat use, stomach contents, and stable isotope signatures (δ15N, δ13C) revealed similar food web structures in the two lakes except for a few differences chiefly related to ecological effects of the invasive vendace. The piscivores had higher Hg concentrations than invertebrate‐feeding fish. Concentrations increased with size and age for the piscivores and vendace, whereas habitat differences were of minor importance. Most fish species showed significant differences in Hg concentrations between the lakes, the highest values typically found in the downstream site where the biomagnification rate also was higher. Mercury levels in piscivorous fish included concentrations that exceed health authorization limits, with possible negative implications for fishing and human consumption. Our findings accentuate the importance of acquiring detailed knowledge of the drivers that can magnify Hg concentrations in fish and how these may vary within and among aquatic systems, to provide a scientific basis for adequate management strategies. Environ Toxicol Chem 2023;42:873–887. © 2023 SETAC [ABSTRACT FROM AUTHOR]

Mangrove ecosystems are known for their role as nursery grounds for some fish. There are mixed and conflicting results on whether fish use mangrove ecosystems primarily for shelter or feeding sites. The purpose of this research is to investigate the relative importance of Avicennia marina organic matter in the feeding of Ilisha melastoma fish in the Mangrove Biosphere Reserve; It was stable isotope approach. Three primary food sources including mangrove tree leaves, microphytobenthos and suspended organic particles were analyzed isotopically. Samples of primary food sources and fish are converted into pure and simple gases such as CO, CO2 and N2 after minimizing their size and turning into powder [1]. Then the identified isotope ratios are compared with a measured standard and the exact amount of isotope formed in the sample is obtained. In this research, sampling was done seasonally in August in the summer season and February in the winter season of 2019 in the mangrove ecosystems of Bandar Khmer, Hormozgan province. Three primary food sources including mangrove tree leaves, microphytobenthos and suspended organic particles were analyzed isotopically. In the summer season, the average stable carbon isotope of primary food sources fluctuated from -28.07 units per thousand for mangrove leaves to -13.58 units per thousand for microphytobenthos. This average in the winter season was obtained from -28.05 units per thousand for mangrove leaves to -13.54 units per thousand for microphytobenthos. The average stable nitrogen isotope of primary food sources in the summer season fluctuated from 1.44 units per thousand for microphytobenthos to 10.72 units per thousand for suspended organic particles. In winter, this amount was calculated from 2.25 units per thousand for microphytobenthos to 8.10 units per thousand for suspended organic particles. The results of this research showed that in the summer season, suspended organic particles with 63% and in the winter season, microphytobenthos with 45% play the most important role in providing the food needed by the small shemsk fish. Investigating the relative importance of mangrove primary products as well as other primary food sources (microphytobenthos and suspended organic particles) in the nutrition of small sea bream using stable isotopes in the mangrove ecosystems of Bandar Khmer showed that the small sea bream has a high nutritional dependence on suspended organic particles in each It has two seasons, summer and winter. Investigating the relative importance of mangrove primary products as well as other primary food sources (microphytobenthos and suspended organic particles) in the nutrition of small sea bream using stable isotopes in the mangrove ecosystems of Bandar Khmer showed that the small sea bream has a high nutritional dependence on suspended organic particles in each It has two seasons, summer and winter. [ABSTRACT FROM AUTHOR]

The warm-water species, striped searobin (Prionotus evolans), has colonized Narragansett Bay (Rhode Island, USA) in recent decades. To clarify the high variability of past investigations, the aim of this study was to characterize the diet of striped searobins. Stomach contents from searobins collected throughout Narragansett Bay in 2019 were identified and analyzed. Diet varied ontogenetically, seasonally, and regionally. The ontogenetic changes in diet reflected an expansion of searobin niche breadth: all searobins ate a diet with sand shrimp; however, smaller searobins ate primarily sand shrimp, while larger searobins also consumed crustaceans and finfish. Searobin diet varied by month, but diet composition did not exhibit a singular trend. Regional variation was illustrated by a dominance of mysid shrimp in Upper-Bay searobin samples, while the Mid- and Lower-Bay samples contained larger proportions of other crustacea and sand shrimp. Their flexible diet provides strong evidence that striped searobins are adaptable generalist feeders. Searobin stomachs included nine prey species of economic importance; such predation could become more common as continued increase of habitat use of searobins in Narragansett Bay may result in greater overlap with the occurrence of vulnerable juvenile stages of economically valuable species (e.g., winter flounder). The results of this work contribute to our understanding of the evolving role of the striped searobin in food webs, particularly those in Southern New England (USA). [ABSTRACT FROM AUTHOR]

To date, direct interactions between pests and natural enemies are often considered in biocontrol programs. Recently there has been an increase of evidence for the importance of third-party mediated indirect interactions in determining the population dynamics of insects. Predicting the strength of such interactions remains a central challenge in biocontrol assessments. Here, two field experiments were performed in two years to investigate to which extent Dysaphis plantaginea Passerini, Aphis pomi De Geer, and Myzus cerasi Fabricius might indirectly interact through shared natural enemies and ants. We first studied the population dynamics of target insects in isolated orchards of apples and cherries. Secondly, we investigated how the spatial coexistence of aphid-infested cherries can indirectly affect the population dynamics of apple aphids via natural enemies and ants. In the first experiment, nine parasitoid species were recorded on apple and cherry aphids, among them were three species in common. Six predatory families were found on cherry and apple aphids, while only one ant species, Lasius niger L., was found associating with these aphids. In the second experiment, temporal variation in the natural enemy-mediated apparent competition between M. cerasi and apple aphids was found. The cherry aphid is likely to be an important source of natural enemies that attack apple aphids early in the season. Significantly reduced numbers of ants associating with apple aphids in the intercropping habitat were found. Our results emphasize the importance of considering indirect interactions in the designing of pest management strategies. [ABSTRACT FROM AUTHOR]

Background: Understanding the relationship between human evolution and environmental changes is the key to lifting the veil on human origin. The hypothesis that environmental changes triggered the divergence of humans from apes (ca. 9.3–6.5 million years ago, Ma) has been poorly tested because of limited continuous environmental data from fossil localities. Lufengpithecus (12.5-6.0 Ma) found on the southeastern margin of the Tibetan Plateau (SEMTP) across the ape–human split provides a good chance for testing this hypothesis. Results: Here, we reconstructed the habitats of L. keiyuanensis (12.5–11.6 Ma) with comprehensive vegetation, climate, and potential food web data by palaeobotanical evidence, together with other multidisciplinary data and partly tested the environment-driven hypothesis by revealing the living conditions of Lufengpithecus. Conclusion: A detailed comparison of hominoids on different continents reveals their behaviour and fate divergence across the ape–human split against the background of global climate change, i.e., the stable living conditions of SEMTP not only provided a so-called 'refuge' for arboreal Lufengpithecus but also acted as a 'double-edged sword', preventing their further evolution while vegetation shifts in East Africa probably stimulated the emergence of human bipedalism, and the intense climatic changes in Europe possibly prevented those hominoids from surviving that time interval. Our findings provide interesting insight into the environmental impacts on the behavioural evolution of hominoids. [ABSTRACT FROM AUTHOR]

Current ecological research and ecosystem management call for improved understanding of the abiotic drivers of community dynamics, including temperature effects on species interactions and biomass accumulation. Allometric trophic network (ATN) models, which simulate material (carbon) transfer in trophic networks from producers to consumers based on mass‐specific metabolic rates, provide an attractive framework to study consumer–resource interactions from organisms to ecosystems. However, the developed ATN models rarely consider temporal changes in some key abiotic drivers that affect, for example, consumer metabolism and producer growth. Here, we evaluate how temporal changes in carrying capacity and light‐dependent growth rate of producers and in temperature‐dependent mass‐specific metabolic rate of consumers affect ATN model dynamics, namely seasonal biomass accumulation, productivity, and standing stock biomass of different trophic guilds, including age‐structured fish communities. Our simulations of the pelagic Lake Constance food web indicated marked effects of temporally changing abiotic parameters on seasonal biomass accumulation of different guild groups, particularly among the lowest trophic levels (primary producers and invertebrates). While the adjustment of average irradiance had minor effect, increasing metabolic rate associated with 1–2°C temperature increase led to a marked decline of larval (0‐year age) fish biomass, but to a substantial biomass increase of 2‐ and 3‐year‐old fish that were not predated by ≥4‐year‐old top predator fish, European perch (Perca fluviatilis). However, when averaged across the 100 simulation years, the inclusion of seasonality in abiotic drivers caused only minor changes in standing stock biomasses and productivity of different trophic guilds. Our results demonstrate the potential of introducing seasonality in and adjusting the average values of abiotic ATN model parameters to simulate temporal fluctuations in food‐web dynamics, which is an important step in ATN model development aiming to, for example, assess potential future community‐level responses to ongoing environmental changes. [ABSTRACT FROM AUTHOR]

In a field trial, agronomic and crop effects of six intercrop mixtures and control (without catch crop) were investigated in maize cultivation. Additionally, the arthropod fauna was recorded with ground traps on in three dates in 2020 (10.-17.7.; 17.8. - 24.8.; 14.9. - 17.9.). The experimental objective was to verify whether the plant biomass remaining on the field (dt DM/ha) and its energy content (GJ/ha) have an impact on the diversity (Shannon-Weaner index) of the arthropod community and its biomass. It was found that the diversity of arthropod community differed significantly between some variants. However, the differences could not be explained by the introduced plant biomass and energy or other factors (number of plant species in the seed mixture, winter hardiness of the catch crops etc.). However, arthropod biomass increased as plant biomass and energy input increased. The result is consistent with literature findings on food web energy transfer and differential resource use by arthropod species. Similarly, the result is discussed in the context of policy approaches to promote insect conservation. [ABSTRACT FROM AUTHOR]

The mortality rate of red-tide dinoflagellates owing to predation is a major parameter that affects their population dynamics. The dinoflagellates Ansanella granifera and Ansanella sp. occasionally cause red tides. To understand the interactions between common heterotrophic protists and A. granifera, we explored the feeding occurrence of nine heterotrophic protists on A. granifera and the growth and ingestion rates of the heterotrophic dinoflagellate Gyrodinium dominans on A. granifera as a function of prey concentration and those of Oxyrrhis marina at a single high prey concentration. The heterotrophic dinoflagellates Aduncodinium glandula, G. dominans, Gyrodinium moestrupii, Luciella masanensis, Oblea rotunda, O. marina, Polykrikos kofoidii, and Pfiesteria piscicida and the naked ciliate Strombidium sp. were able to feed on A. granifera. With increasing mean prey concentrations, the growth and ingestion rates of G. dominans feeding on A. granifera rapidly increased and became saturated or slowly increased. The maximum growth and ingestion rates of G. dominans on A. granifera were 0.305 d-1 and 0.42 ng C predator-1 d-1 (3.8 cells predator-1 d-1), respectively. Furthermore, the growth and ingestion rates of O. marina on A. granifera at 1,700 ng C mL-1 (15,454 cells mL-1) were 0.037 d-1 and 0.19 ng C predator-1 d-1 (1.7 cells predator-1 d-1), respectively. The growth and ingestion rates of G. dominans and O. marina feeding on A. granifera were almost the lowest among those on the dinoflagellate prey species. Therefore, G. dominans and O. marina may prefer A. granifera less than other dinoflagellate prey species. The low mortality rate of A. granifera may positively affect its bloom formation. [ABSTRACT FROM AUTHOR]

Encounters between flowers and invertebrates are key events for the functioning of tropical forests. Assessing the structure of networks composed of the interactions between those partners leads to a better understanding of ecosystem functioning and the effects of environmental factors on ecological processes. Gathering such data is, however, costly and time‐consuming, especially in the highly diverse tropics. We aimed to provide a comprehensive repository of available flower–invertebrate interaction information for the Atlantic Forest, a South American tropical forest domain. Data were obtained from published works and "gray literature," such as theses and dissertations, as well as self‐reports by co‐authors. The data set has ~18,000 interaction records forming 482 networks, each containing between one and 1061 interaction links. Each network was sampled for about 200 h or less, with few exceptions. A total of 641 plant genera within 136 different families and 39 orders were reported, with the most abundant and rich families being Asteraceae, Fabaceae, and Rubiaceae. Invertebrates interacting with these plants were all arthropods from 10 orders, 129 families, and 581 genera, comprising 2419 morphotypes (including 988 named species). Hymenoptera was the most abundant and diverse order, with at least six times more records than the second‐ranked order (Lepidoptera). The complete data set shows Hymenoptera interacting with all plant orders and also shows Diptera, Lepidoptera, Coleoptera, and Hemiptera to be important nodes. Among plants, Asterales and Fabales had the highest number of interactions. The best sampled environment was forest (~8000 records), followed by pastures and crops. Savanna, grasslands, and urban environments (among others) were also reported, indicating a wide range of approaches dedicated to collecting flower–invertebrate interaction data in the Atlantic Forest domain. Nevertheless, most reported data were from forest understory or lower strata, indicating a knowledge gap about flower–invertebrate interactions at the canopy. Also, access to remote regions remains a limitation, generating sampling bias across the geographical range of the Atlantic Forest. Future studies in these continuous and hard‐to‐access forested areas will yield important new information regarding the interactions between flowers and invertebrates in the Atlantic Forest. There are no copyright restrictions on the data set. Please cite this data paper if the data are used in publications and teaching events. [ABSTRACT FROM AUTHOR]

Artificial light at night (ALAN) affects species' physiology and behaviour, and the interactions between species. Despite the importance of plants as primary producers, it remains poorly understood whether and how effects of ALAN on plants cascade through the food web.We assess the extent to which ALAN of different spectra result in plant‐mediated insect herbivory damage. In a 6‐month field experiment, we exposed plants of differing palatability to three colours of ALAN and a dark control, and assessed plant traits (growth rate, leaf size, foliar density and thickness) and insect herbivory (represented by insect damage as loss of foliage to leaf‐chewing insects, and gall abundance by phloem‐feeding herbivory).We found evidence for plant trait‐mediated ALAN effects on herbivory for oak, but not for blueberry. In oak, ALAN of different colours changed the direction of relationships of insect damage with relative growth rate and with leaf thickness. Moreover, we found that the effects of ALAN on herbivory damage differed markedly between forest types within the same locale, particularly in the red light treatment.Synthesis and applications. Our results provide evidence that continuous night‐time light, as provided by street lighting around the world, affects food web interactions. The nature of these effects differed by species and appeared to depend on forest type and the light spectrum employed, thus underlining the context dependency of ALAN in different ecosystems and environmental settings. These findings highlight the complexity of using spectral manipulation as a mitigation measure, and the need for further consideration of ALAN in environmental management and planning, to limit the exposure and impact of cascading effects of artificial light at night on food webs and communities. [ABSTRACT FROM AUTHOR]

Formalin preservation affects the stable isotope composition of zooplankton samples, thus limiting the analysis of valuable collections covering large time intervals. Here, we compare different procedures for correcting the bias caused by formalin in δ13C and δ15N of zooplankton community samples. Zooplankton samples representative of seasonal variations in the period 2000–2009 were collected off A Coruña (NW Spain). Part of the sample was immediately dried and analysed for δ13C, δ15N, and elemental composition within 3 years of collection. These values were used as the unpreserved reference. The remaining sample was preserved in 4% formaldehyde and aliquots obtained after a period ranging from 3 years to more than 10 years of storage were analysed as the originally dried samples. Additionally, the copepod fraction of total biomass was determined in the preserved samples. Corrections of formalin effects based on ordinary least squares regression had large uncertainties, while mass balance corrections based on the change in C:N ratio (only possible for δ13C) overestimated reference values. However, either simple corrections based on the mean difference between values in dry and preserved samples or more complex generalised additive models considering seasonality, copepod biomass, and time of sample storage, produced estimations with relatively low uncertainty. Our results highlight the importance of determining specific correction solutions for each preserved collection before reconstructing stable isotope time series. Furthermore, the uncertainties associated with the estimates can be used in sensitivity analysis to assess their potential impact on the interpretation of the series. [ABSTRACT FROM AUTHOR]

Epigeic generalist predators play a crucial role in terrestrial ecosystems, connecting aboveground and belowground food webs. Using stable isotope compositions (δ13C and δ15N values), we assessed the trophic niches of the two main groups of generalist predators (ground beetles (Coleoptera, Carabidae) and spiders (Arachnida: Aranei)), as well as their potential prey (phytophagous and saprophagous insects), plants, and soils in the forest, steppe, and transitional ecosystems located in the forest–steppe of southwestern Siberia. We hypothesized that (1) the trophic niche of carabids is wider than that of spiders, because some ground beetles are omnivorous, and (2) the contribution of invertebrates from the detrital food web (saprophages) to the diet of generalist predators is higher in the "detrital" forest ecosystem than in the steppe, which should be reflected in increased δ13C and δ15N values of the predators in the forest. In total, 16 species of carabid and 17 species of spider were analyzed. The δ15N values of ground beetles suggested a wide range of trophic niches corresponding to two or three trophic levels. Omnivorous carabids of the genera Amara and Harpalus had the minimum δ15N values. The carbon isotope compositions of the ground beetles suggests that most predatory species were predominantly involved in grazing food chains. Spiders had on average increased δ15N values compared to ground beetles, and a relatively narrow range of δ15N values. The isotopic niche occupied by spiders hardly overlapped with the isotopic niche of carabids, which may indicate a significant difference in the range of consumed resources. Thus, our data suggest a significant difference in the trophic niches of the key generalist predators, ground beetles and spiders, which was observed both in the forest and the steppe habitats. Spiders appear to be more closely associated with detrital food webs than ground beetles. Contrary to our expectations, we did not find higher δ13C and δ15N values in ground-dwelling generalist predators in the forest compared to the steppe ecosystem. [ABSTRACT FROM AUTHOR]

Within the context of the ecosystem approach to fisheries management, an ecosystem model was developed for the Balearic Islands in the early 2000s, covering from 0 to 800 m of depth. The aim of the study was to describe the structure and functioning of the ecosystem together with the fishing impacts. The results show that the biomass of the primary producers (PP), mainly dominated by Posidonia oceanica meadows and red algae beds, represented a high percentage of the biomass (39.20%) in the ecosystem. Most of the trophic flows occurred between PP (mostly benthic) and trophic level II. The mixed trophic impact analysis also highlighted a positive impact of the functional groups (FGs) at the base of the food web. Besides, there were important trophic flows between several demersal FGs, and many groups of the pelagic compartment, confirming the importance of the benthopelagic coupling previously reported. The mean trophic level of the catch (mTLc=2.76) was lower than those reported in adjacent areas due to the discard of benthic producers. By excluding benthic PP, the Balearic Islands showed the highest mTLc (3.44) among all the Mediterranean areas modelled, probably due to differences in the trophic structure, lower fisheries exploitation levels and lower development of the purse seine fleet targeting small pelagic fishes. The mean transfer efficiency (21.80%) was double than the global average (10%), which highlights the oligotrophy of the system, the importance of demersal production which has lower rates of transfer through the food web, and a more efficient use of nutrients in the ecosystem. Sponges, one of the most important groups of benthic invertebrates in the Balearic Archipelago, are known to recycle dissolved organic matter, which is reintroduced into the food web similar to the microbial loop, but the magnitude of this and other processes remains still unknown in this area. The present study is a first step to develop spatio-temporal simulations under different exploitation scenarios and to calculate ecological indicators to assess the state of the marine environment in this region.

Grand Lake St. Marys (GLSM) is a popular recreational lake located in western Ohio, United States, generating nearly $150 million in annual revenue. However, recurring algal blooms dominated by Planktothrix agardhii, which can produce harmful microcystin toxins, have raised concerns about water safety and negatively impacted the local economy. Planktothrix agardhii is host to a number of parasites and pathogens, including an obligate fungal parasite in the Chytridiomycota (chytrids). In this study, we investigated the potential of these chytrid (Rhizophydium sp.) to infect P. agardhii blooms in the environment by modifying certain environmental conditions thought to limit infection prevalence in the wild. With a focus on temperature and water mixing, mesocosms were designed to either increase or decrease water flow compared to the control (water outside the mesocosm). In the control and water circulation mesocosms, infections were found infrequently and were found on less than 0.75% of the Planktothrix population. On the other hand, by decreasing the water flow to stagnation, chytrid infections were more frequent (found in nearly 3x as many samples) and more prevalent, reaching a maximum infection rate of 4.12%. In addition, qPCR coupled with 16S–18S sequencing was utilized to confirm the genetic presence of both host and parasite, as well as to better understand the effect of water circulation on the community composition. Statistical analysis of the data confirmed that chytrid infection was dependent on water temperature, with infections predominantly occurring between 19°C and 23°C. Additionally, water turbulence can significantly reduce the infectivity of chytrids, as infections were mostly found in stagnant mesocosms. Further, decreasing the water circulation promoted the growth of the cyanobacterial population, while increasing water agitation promoted the growth of green algae (Chlorophyta). This study starts to explore the environmental factors that affect chytrid pathogenesis which can provide valuable insights into controlling measures to reduce the prevalence of harmful algal blooms and improve water quality in GLSM and similarly affected waterbodies.

Invertebrates play vital roles in maintaining biodiversity and food web structure. However, it is difficult to identify invertebrate taxa across complex habitats due to the limitation of traditional morphology. In subtropical wetlands, environmental DNA (eDNA) metabarcoding was used to characterize the composition and diversity of aquatic invertebrates and analyze the environmental impacts on invertebrate community structure. According to the relative abundance (%) of invertebrate OTU richness, 30 sampling sites in wetlands were clustered into six zones, which exhibited significant spatial (i.e., wetland type-specific) differences in taxonomic composition. The relative OTU abundance (%) at the phylum level showed that Cnidaria (48.5%) > Porifera (19.4%) > Rotifera (11.0%) > Mollusca (9.2%) > Annelida (5.3 ± 2.8%) > others (less than 2.2%). Of the five alpha diversity indexes, ‘Simpson’ was the most effective index to distinguish the spatial differences in invertebrate diversity, and the class-level alpha diversity showed higher recognition than other taxonomic levels. The class-level biomarkers that could indicate the habitat-specific composition of local invertebrates were Insecta, Cnidaria, Hydrozoa, and Gastropoda in the inflow river; Ascidiacea and Demospongiae in the fluvial wetland; Clitellata, Gymnolaemata, and Monogononta in the lacustrine wetland; and Echinoidea in the estuarine wetland. The associations between environmental factors and invertebrate OTU richness based on redundancy analysis showed the taxon-level tendency of phylum (78.5%) > class (73.4%) > order (69.3%) > family (64.9%) > genus (61.2%). Our results demonstrated that aquatic invertebrate diversity profiling by environmental DNA metabarcoding can effectively reflect the composition, diversity and biomarkers of invertebrate communities. In the future, because of its great application potential, the eDNA technique may play an important role in biomonitoring complex water environments.

The seasonal feeding patterns of the cold-adapted fish, Coregonus albula, are poorly studied in high-latitude lakes but could provide insight for predicting the effects of global warming. We examined vendace’s diet composition, traced the carbon and nitrogen isotope ratios from producers to consumers in the food web, and estimated vendace’s trophic position in a subarctic lake (the White Sea basin). Results showed the vendace to be a typical euryphagous fish, but clear seasonal differences were found in the relative importance of plankton and benthos in the diet. The vendace consumed primarily benthic amphipods in the summer, planktonic cladocerans in the autumn, and copepods in the winter–spring (under ice); larvae of aquatic insects were the second-most important food items throughout the year. Because of the substantial proportion of fish embryos in its diet, the vendace had a trophic position similar to that of a predatory fish (perch). The Bayesian food source-mixing model revealed that the majority of vendace energy derives from planktonic copepods. The dominant Cyclops had the lowest carbon isotope values, suggesting a carbon-depleted diet typical for methanotrophic bacteria, as its probable food source was in a lake under ice. Understanding the feeding patterns of vendace provides information to better predict the potential biotic effects of environmental change on lake ecosystems.

IntroductionFood web is an important basis for identifying trophodynamic processes, and evaluating the structural and functional characteristics of ecosystems. The trophodynamics and system function of artificial reef (AR) ecosystems have rarely been examined.MethodsStable isotope analysis was used to investigate the food web structure and functions of an artificial reef (AR) ecosystem in this study.Results and DiscussionThe δ13C and δ15N values of particulate organic matter (POM) in AR showed noticeable seasonal changes, and the δ13C value of POM in autumn was significantly higher than that in other seasons (p

The fatty acid composition in organisms can reflect the trophic level, feeding habits, and utilization of local resources. In the present study, the living resources of different functional areas (artificial reef area, shellfish area, macroalgae area) in the Zhelin Bay Marine Ranch were investigated, and fatty acid analysis was used to elucidate the trophic relations across the food web. The results showed that 22:6ω3 FA (docosahexaenoic acid, DHA), 20:5ω3 FA (eicosapentaenoic acid, EPA), 16:1ω7 FA, and 16:0 FA are fatty acid biomarkers that distinguish carnivorous, omnivorous, and herbivorous organisms. The ratios of DHA/EPA, polyunsaturated fatty acids/saturated fatty acids (PUFA/SFA), and sum of ω3 fatty acids/sum of ω6 fatty acids (Σω3/Σω6) can be used as an important basis to assess the trophic level and feeding habits of organisms. In the comparison of the food web structure of different functional areas, the DHA/EPA ratio of carnivorous organisms in the Artificial Reef area was higher than that in other functional areas due to the abundant living resources, indicating that the food web of the Artificial Reef area presents lower stability to cope with perturbations. Furthermore, MixSIAR was used to quantitatively estimate the diet composition of consumers in the Zhelin Bay Marine Ranch based on their fatty acids. The results of the present study are a valuable contribution to understanding the trophic relationships in the Zhelin Bay Marine Ranch and provide theoretical support for future planning and construction of marine ranches.

Stable isotopes such as δ13C and δ15N are routinely used in trophic ecology as isotope values are derived from diet and recorded subsequent fractionation in consumer tissue. However, this approach necessitates to estimate a priori the fractionation between food source and consumer leading to potential uncertainties. In this context, the development of additional biomarkers enables to have better resolution on feeding habits. Dissolved Inorganic Carbon (DIC) from volcanic activity and bacteria using this DIC presents a strongly depleted natural radiocarbon abundances (Δ14C). Through its activity, the geothermal plant of Bouillante in Guadeloupe (French West Indies) releases sulfur bacteria in shallow environment of the Bay. A previous study reveals ingestion of those bacteria by opportunist species (sea urchin and fish species). In the present study, ten species with different diet and feeding mode were sampled close to the release channel of the geothermal plant and in a control station in order to simultaneously determine their stable isotopes (δ13C and δ15N) and radiocarbon compositions. Compared to models using Δ14C data, models using δ13C and δ15N data underestimate the role of bacteria in diet of urchin and fish species whereas this role is overestimated for all other species. Compared to previous models, radiocarbon would give more realistic and reliable results than the classical use of stable isotope. This study confirms the utility of radiocarbon in food web ecology, particularly at the ecosystems having food sources with contrasting Δ14C values.

Abstract Current ecological research and ecosystem management call for improved understanding of the abiotic drivers of community dynamics, including temperature effects on species interactions and biomass accumulation. Allometric trophic network (ATN) models, which simulate material (carbon) transfer in trophic networks from producers to consumers based on mass‐specific metabolic rates, provide an attractive framework to study consumer–resource interactions from organisms to ecosystems. However, the developed ATN models rarely consider temporal changes in some key abiotic drivers that affect, for example, consumer metabolism and producer growth. Here, we evaluate how temporal changes in carrying capacity and light‐dependent growth rate of producers and in temperature‐dependent mass‐specific metabolic rate of consumers affect ATN model dynamics, namely seasonal biomass accumulation, productivity, and standing stock biomass of different trophic guilds, including age‐structured fish communities. Our simulations of the pelagic Lake Constance food web indicated marked effects of temporally changing abiotic parameters on seasonal biomass accumulation of different guild groups, particularly among the lowest trophic levels (primary producers and invertebrates). While the adjustment of average irradiance had minor effect, increasing metabolic rate associated with 1–2°C temperature increase led to a marked decline of larval (0‐year age) fish biomass, but to a substantial biomass increase of 2‐ and 3‐year‐old fish that were not predated by ≥4‐year‐old top predator fish, European perch (Perca fluviatilis). However, when averaged across the 100 simulation years, the inclusion of seasonality in abiotic drivers caused only minor changes in standing stock biomasses and productivity of different trophic guilds. Our results demonstrate the potential of introducing seasonality in and adjusting the average values of abiotic ATN model parameters to simulate temporal fluctuations in food‐web dynamics, which is an important step in ATN model development aiming to, for example, assess potential future community‐level responses to ongoing environmental changes.

IntroductionSediment and nutrients flow into estuary with runoff, and then influence the estuary ecosystem. Much work has been done for investigating the response of water quality and species group (eg. phytoplankton or zooplankton) to the runoff from upstream, while few research has been taken to evaluate the response of the whole ecosystem.MethodsFood webs of different seasons and regions were established based on stable isotope analysis and Bayesian mixing model. The influences of upstream runoff and sediment transport on the estuarine food webs were analyzed.ResultsFood web in estuary had highly spatial-temporal variability. The stable isotope values of organisms were higher on the northern shore than that on the southern shore. The area with high-turbidity freshwater inflow nurtured more terrestrial- organic- matter (TOM) relying species. And the contribution of TOM to food web was higher in flood season than that in non-flood season. The trophic levels of major consumers in the non-flood season were generally higher than that in the flood season. Significant differences in the average TP of species between two shores appeared during the non-flood season (P < 0.05). Expect for the C value, all of the topological indexes of food webs on the northern shore were higher than those on the southern shore, and they were higher in the flood period.DiscussionThe input and diffusion of sediment and nutrients carried by runoff led to the changes in the dietary structure of estuarine organisms and the decrease in trophic levels of major consumers. At the same time, flow pulse with high sediment also aggravated the spatial differences of the structure of food webs. The higher contribution of TOM to consumers increased the link density of food web on the southern shore, making it a more robust system. However, the high diversity of food sources and aquatic species made the food web more complex on the northern shore.

Introduction: La Segua is an important wetland in Ecuador, recognized as a Ramsar site and of great ecological relevance. Currently, La Segua is threatened by human pressures and unsustainable landscape use associated with agriculture and aquaculture. This study is the first approach to the occurrence of suspended microplastics (SMPs) in an Ecuadorian lentic waterbody and the estimated potential threat of these on the filter and suspension feeders in aquatic food webs.Methods: Surface water samples were collected at 16 sampling points in the wetland to analyze the occurrence, concentration, and horizontal distribution of Suspected Suspended Microplastics (SSMPs) and zooplankton.Results and discussion: SSMPs were found in all sampling sites, and concentrations were between 313 and 490 particles/liter. Fragments were the most abundant category, followed by fibers, films, and pellets. The highest concentration of SSMPs was found in sampled sites on the east coast and in the middle of the wetland. The frequency and concentration of categories of SSMps found in surface water largely reflect the reality of local human activity around the La Segua wetland. Only rotifers and copepod nauplii were found in the zooplankton. The SSMMPs to zooplankton ratio varied between 0.3 and 441 particles/individuals.The SSMPs/zooplankton ratio indicates that fish and other filter and suspension feeders of aquatic food webs could be more likely to feed on suspended microplastics than natural food items around the wetland. SSMPs indicate that microplastics may represent.

Porpita porpita occurs in the tropical and sub-tropical waters of the Pacific, Atlantic, and Indian Oceans, and the mass numbers of stranded colonies seem to be increasing. Although its presence in Indian waters is minimal, this is the first record ever made of P. porpita in Visakhapatnam coastal waters. The present study provided a detailed description of the species and its global distribution. Further, the perceived increase in gelatinous zooplankton blooms in the observed area indicates that jellyfish can negatively affect fisheries because they compete with zooplanktivorous fish, prey upon fish eggs and larvae, and indirectly compete with higher trophic levels by reducing the plankton available to planktivores. Conversely, jellyfishes also play a vital role in regulating global marine plankton food webs, spatio-temporal dynamics, and biomass, which is a role that has been generally neglected so far.

The relationship between biodiversity and ecosystem functions (BEFs) has attracted great interest. Studies on BEF have so far focused on the average trend of ecosystem function as species diversity increases. A tantalizing but rarely addressed question is why large variations in ecosystem functions are often observed across systems with similar species diversity, likely obscuring observed BEFs.Here we use a multi‐trophic food web model in combination with empirical data to examine the relationships between species richness and the variation in ecosystem functions (VEFs) including biomass, metabolism, decomposition, and primary and secondary production. We then probe the mechanisms underlying these relationships, focusing on the role of trophic interactions.While our results reinforce the previously documented positive BEF relationships, we found that ecosystem functions exhibit significant variation within each level of species richness and the magnitude of this variation displays a hump‐shaped relationship with species richness. Our analyses demonstrate that VEFs is reduced when consumer diversity increases through elevated nonlinearity in trophic interactions, and/or when the diversity of basal species such as producers and decomposers decreases. This explanation is supported by a 34‐year empirical food web time series from the Gulf of Riga ecosystem.Our work suggests that biodiversity loss may not only result in ecosystem function decline, but also reduce the predictability of functions by generating greater function variability among ecosystems. It thus helps to reconcile the debate on the generality of positive BEF relationships and to disentangle the drivers of ecosystem stability. The role of trophic interactions and the variation in their strengths mediated by functional responses in shaping ecosystem function variation warrants further investigations and better incorporation into biodiversity—ecosystem functioning research. [ABSTRACT FROM AUTHOR]

Eutrophication is a global aquatic environmental problem. Traditional biomanipulation targeting keystone species has been effective for restoring eutrophic lakes. In this study, we conducted monthly fishery assessments and identified keystone species in Zhushan Bay of Taihu Lake, the most representative lake in the middle and lower reaches of the Yangtze River. We built the topological structure of Zhushan Bay's food web based on feeding relationships and calculated network indices of fish groups in the food web using network analysis, combined with Key Player Problem operation. Culter mongolicus, Culter alburnus, Protosalanx hyalocranius and Salangichthys tangkahkeii were the keystone species in Zhushan Bay's food web. Culter mongolicus and Culter alburnus had the greatest impact on the food web after removal. Protosalanx hyalocranius had the fastest speed of transmitting information. Salangichthys tangkahkeii was the key baitfish with the strongest ability to determine structure of species in higher trophic levels. Our study provided a reference for scientific management of shallow lake ecosystems and biological solutions for restoration of eutrophic lakes. [ABSTRACT FROM AUTHOR]

Molecular gut content analysis is a popular tool to study food web interactions and has recently been suggested as an alternative source for DNA‐based biomonitoring. However, the overabundant consumer's DNA often outcompetes that of its diet during PCR. Lineage‐specific primers are an efficient means to reduce consumer amplification while retaining broad specificity for dietary taxa. Here, we designed an amplicon sequencing assay to monitor the eukaryotic diet of mussels and other metazoan filter feeders and explore the utility of mussels as natural eDNA samplers to monitor planktonic communities. We designed several lineage‐specific rDNA primers with broad taxonomic suitability for eukaryotes. The primers were tested using DNA extracts of different limnic and marine mussel species and the results compared to eDNA water samples collected next to the mussel colonies. In addition, we analysed several 25‐year time series samples of mussels from German rivers. Our primer sets efficiently prevent the amplification of mussels and other metazoans. The recovered DNA reflects a broad dietary preference across the eukaryotic tree of life and considerable taxonomic overlap with filtered water samples. We also show the utility of a reversed version of our primers, which prevents amplification of nonmetazoan taxa from complex eukaryote community samples, by enriching fauna associated with the marine brown algae Fucus vesiculosus. Our protocol will enable large‐scale dietary analysis in metazoan filter feeders, facilitate aquatic food web analysis and allow surveying of aquacultures for pathogens. Moreover, we show that mussels and other aquatic filter feeders can serve as complementary DNA source for biomonitoring. [ABSTRACT FROM AUTHOR]

Background. Range maps are a useful tool to describe the spatial distribution of species. However, they need to be used with caution, as they essentially represent a rough approximation of a species' suitable habitats. When stacked together, the resulting communities in each grid cell may not always be realistic, especially when species interactions are taken into account. Here we show the extent of the mismatch between range maps, provided by the International Union for Conservation of Nature (IUCN), and species interactions data. More precisely, we show that local networks built from those stacked range maps often yield unrealistic communities, where species of higher trophic levels are completely disconnected from primary producers. Methodology. We used the well-described Serengeti food web of mammals and plants as our case study, and identify areas of data mismatch within predators' range maps by taking into account food web structure. We then used occurrence data from the Global Biodiversity Information Facility (GBIF) to investigate where data is most lacking. Results. We found that most predator ranges comprised large areas without any overlapping distribution of their prey. However, many of these areas contained GBIF occurrences of the predator. Conclusions. Our results suggest that the mismatch between both data sources could be due either to the lack of information about ecological interactions or the geographical occurrence of prey. We finally discuss general guidelines to help identify defective data among distributions and interactions data, and we recommend this method as a valuable way to assess whether the occurrence data that are being used, even if incomplete, are ecologically accurate. [ABSTRACT FROM AUTHOR]

Nanotechnology (NT) in the past and current decade has gained a lot of attention due to its potent antibacterial activities and its unique physicochemical features. NT works based on nanoparticles in which silver nanoparticles (AgNPs) are one of the most vital and fascinating nanomaterials. Therefore, AgNPs have been used for a variety of items, with encouraging outcomes. Besides the significant applications, there is a lot of disagreement over how AgNPs interact with the environment and how hazardous they are to aquatic life. Most worldwide freshwater ecosystems are polluted by AgNPs-containing effluents discharged from sewage and wastewater treatment plants and/or runoff streams. In the aquatic food web, fish acquire higher trophic levels; therefore, AgNPs accumulation in the body is inevitable. The bioaccumulation of AgNPs causes numerous toxic effects such as inflammation, oxidative stress, tissue disruption, and intestinal bacterial dysbiosis which could possibly lead to death. Therefore, this study aimed to describe the fate of AgNPs in the food web, their transformation and accumulation, and their possible consequences in fish. The various causes of toxicity within the fish body and the detrimental impacts on the aquatic ecosystem still require more in-depth study. [ABSTRACT FROM AUTHOR]