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The Falkland Islands marine environment host a mix of temperate and subantarctic species. This review synthesizes baseline information regarding ontogenetic migration patterns and trophic interactions in relation to oceanographic dynamics of the Falkland Shelf, which is useful to inform ecosystem modelling. Many species are strongly influenced by regional oceanographic dynamics that bring together different water masses, resulting in high primary production which supports high biomass in the rest of the food web. Further, many species, including those of commercial interest, show complex ontogenetic migrations that separate spawning, nursing, and feeding grounds spatially and temporally, producing food web connections across space and time. The oceanographic and biological dynamics may make the ecosystem vulnerable to climatic changes in temperature and shifts in the surrounding area. The Falkland marine ecosystem has been understudied and various functional groups, deep-sea habitats and inshore-offshore connections are poorly understood and should be priorities for further research. [ABSTRACT FROM AUTHOR]

The electrolytes Na and K both function to maintain water balance and membrane potential. However, these elements work differently in plants—where K is the primary electrolyte—than in animals—where ATPases require a balanced supply of Na and K. Here, we use monthly factorial additions of Na and K to simulate bovine urine inputs and explore how these electrolytes ramify through a prairie food web. Against a seasonal trend of increasing grass biomass and decreasing water and elemental tissue concentrations, +K and +Na plots boosted water content and, when added together, plant biomass. Compared to control plots, +Na and +K plots increased element concentrations in above‐ground plant tissue early in summer and decreased them in September. Simultaneously, invertebrate abundance on Na and K additions were sequentially higher and lower than control plots from June to September and were most suppressed when grass was most nutrient rich. K was the more effective plant electrolyte, but Na frequently promoted similar changes in grass ionomes. The soluble/leachable ions of Na and K showed significant ability to shape plant growth, water content, and the 15‐element ionome, with consequences for higher trophic levels. Grasslands with high inputs of Na and K—via large mammal grazers or coastal aerosol deposition—likely enhance the ability of plants to adjust their above‐ground ionomes, with dramatic consequences for the distribution of invertebrate consumers. [ABSTRACT FROM AUTHOR]

Simple Summary: When there are multiple natural enemies in the same ecosystem, intraguild predation between natural enemies will affect the population dynamics of target organisms and the effectiveness of biological control. It is necessary to study this relationship in depth to enhance the function of biological control. Hippodamia variegata (Goeze) and parasitoids are two types of dominant natural enemies of the cotton aphid Aphis gossypii Glover in Xinjiang, China. Among them, the ladybeetle preys on common aphids as well as parasitoids. This study measured the feeding choices of H. variegata towards mummies with different densities of A. gossypii. Meanwhile, investigation and sampling in the cotton field were conducted from 2017 to 2019. The predation of H. variegata individuals on aphids and mummies was detected using diagnostic PCR. The results showed that H. variegata had no obvious feeding preference towards live aphids and mummies, and preferred denser prey. The molecular detection results show that A. gossypii was the main prey source and medium of consumption of parasitoids for the ladybeetle. H. variegata had strong trophic links to both parasitoids and aphids. The above information is crucial for evaluating the pest control ability of H. variegata more comprehensively and strengthening the strategies for the biological control of aphids. Intraguild predation among arthropod predators in agricultural ecosystems may have a negative impact on biological control. At present, there are few direct reports on trophic relationships among participants of predation in field groups. In this study, we measured the feeding choices of Hippodamia variegata (Goeze) towards mummies with different densities of Aphis gossypii Glover. The dynamics of the occurrence of mummies in the cotton field were investigated over 2017–2019. Singleplex PCR and multiplex PCR were used to detect the predation of 2090 H. variegata individuals on aphids and mummies in Xinjiang cotton field, which revealed the intraguild predation frequency between H. variegata and various parasitoids. There was no obvious feeding preference of H. variegata towards live aphids or mummies, which mainly depended on the relative density of prey. Among the four species of aphids detected in H. variegata, A. gossypii had a high detection rate and was the main prey source of the ladybeetle in the cotton filed. Mostly, ladybeetles consumed parasitoids through mummies, with 6.39% directly feeding on adult parasitoids. H. variegata had strong trophic links to both parasitoids and aphids. We established a food web of aphids–primary parasitoids–hyperparasitoids–H. variegata, which can be used to evaluate the pest control ability of H. variegata from a new perspective. [ABSTRACT FROM AUTHOR]

Biotic interactions are a key component of the proper functioning of ecosystems. However, information on biotic interactions is spatially and taxonomically biased and limited to several groups. The most efficient strategy to fill these gaps is to combine spatial information (species ranges) with different sources of information (functional and field data) to infer potential interactions. This approach is possible due to the fact that there is a correspondence between the traits of two trophic levels (e.g., predator and prey sizes are correlated). Therefore, our objective was to evaluate the performance of the joint use of spatial, functional and field data to infer properties of the predator–prey interaction for five neotropical cats. To do this, we used presence–absence matrices to obtain lists of potential prey species per grid-cell for each predator range. These lists were filtered according to different criteria (models), and for each model, an interaction property was estimated and compared with field observations. Our results show that the use of functional information and co-occurrence allows us to generate values similar to those observed in the field. We also observed that there were differences in model performance related to the intrinsic characteristics of the predator (body size) and the interaction property being evaluated. [ABSTRACT FROM AUTHOR]

Microplastics (MPs) constitute a serious environmental issue in today's society, a product of the modern way of life, in which everything happens at great speed and where single-use plastic products have contributed to dispersing plastics around the globe. In this review work, the current situation in terms of characterization and the improvements that are necessary for its optimization are presented. The effects of microplastics on the environment (water, land, and air), food webs and the mechanisms through which can be transferred from microorganisms to higher beings, as well as its effect on humans are also discussed. [ABSTRACT FROM AUTHOR]

Quantifying species trophic interaction strengths is crucial for understanding community dynamics and has significant implications for pest management and species conservation. DNA‐based methods to identify species interactions have revolutionized these efforts, but a significant limitation is the poor ability to quantify the strength of trophic interactions, that is the biomass or number of prey consumed. We present an improved pipeline, called Lazaro, to map unassembled shotgun reads to a comprehensive arthropod mitogenome database and show that the number of prey reads detected is quantitatively predicted from the prey biomass consumed, even for indirect predation. Two feeding bioassays were performed: starved coccinellid larvae consuming different numbers of aphids (Prey Quantity bioassay), and starved coccinellid larvae consuming a chrysopid larvae that had consumed aphids (Direct and Indirect Predation bioassay). Prey taxonomic assignment against a mitochondrial genome database had high accuracy (99.8% positive predictive value) and the number of prey reads was directly related to the number of prey consumed and inversely related to the elapsed time since consumption with high significance (r2 =.932, p = 4.92E‐6). Aphids were detected up to 6 h after direct predation plus 3 h after indirect predation (9 h in total) and detection was related to the predator‐specific decay rates. Lazaro enabled quantitative predictions of prey consumption across multiple trophic levels with high taxonomic resolution while eliminating all false positives, except for a few confirmed contaminants, and may be valuable for characterizing prey consumed by field‐sampled predators. Moreover, Lazaro is readily applicable for species diversity determination from any degraded environmental DNA. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Vector‐borne pathogen transmission is shaped by multiple abiotic and biotic factors. Understanding the relative importance of these factors on vector abundance and infection is important for developing vector‐borne disease control strategies. The crown of the Attalea butyracea palm provides a natural arboreal mesocosm suitable for studying how food web relations and microclimate affect Chagas disease vectors of the genus Rhodnius, which feed on vertebrate blood and interact with many vertebrate and invertebrate species, vegetation, and detritus within the palm crown. We performed a cross‐sectional, observational study of A. butyracea crowns using a community ecology network approach to evaluate abiotic and biotic conditions associated with Rhodnius pallescens abundance and infection with Trypanosoma cruzi, the Chagas disease etiologic agent. We collected 1098 R. pallescens from 105 A. butyracea crowns in rural landscapes of Panama. In a palm subset (N = 49), we recorded microclimate and habitat conditions and counted vertebrate and invertebrate species in order to characterize palm crown food webs. We used food web metrics, namely Generality (average number of prey per predator) and Vulnerability (average number of predators per prey) to evaluate associations between palm community trophic structure, vector predators, vector blood meal species composition, vector abundance, and vector T. cruzi infection. Field data analyzed with generalized linear models showed that vector abundance and infection in a given palm crown were influenced by a combination of geographic location, land‐use type, palm crown animal community composition, and microhabitat conditions. Vector abundance was negatively associated with increased overall palm crown community diversity. However, vector abundance was positively associated with the invertebrate predator and mammal community. R. pallescens Vulnerability score, which measures predation pressure on the vector within the palm crown, was positively associated with vector abundance. Vector infection with T. cruzi was positively associated with mammal presence; vectors in palms with mammals were about 25 times more likely to be infected with T. cruzi compared with vectors in palms without mammals. Our findings suggest that a holistic study of food webs and environmental variables at the local scale can provide useful information for vector‐borne disease management across a wide habitat range. [ABSTRACT FROM AUTHOR]

Parasites form an integral part of food webs, however, they are often ignored in classic food web theory or limited to the investigation of trophic transmission pathways. Specifically, direct consumption of parasites by nonhost predators is rarely considered, while it can contribute substantially to energy flow in food webs. In aquatic systems, chytrids constitute a major group of fungal parasites whose free‐living infective stages (zoospores) form a highly nutritional food source to zooplankton. Thereby, the consumption of zoospores can create an energy pathway from otherwise inedible phytoplankton to zooplankton ("mycoloop"). This parasite‐mediated energy pathway might be of special importance during phytoplankton blooms dominated by inedible or toxic primary producers like cyanobacteria, which are on the rise with eutrophication and global warming. We theoretically investigated community dynamics and energy transfer in a food web consisting of an edible nonhost and an inedible host phytoplankton species, a parasitic fungus, and a zooplankton species grazing on edible phytoplankton and fungi. Food web dynamics were investigated along a nutrient gradient contrasting nonadaptive zooplankton species representative for filter feeders like cladocerans and zooplankton with the ability to actively adapt their feeding preferences like many copepod species. Overall, the importance of the mycoloop for zooplankton increases with nutrient availability. This increase is smooth for nonadaptive consumers. For adaptive consumers, we observe an abrupt shift from an almost exclusive preference for edible phytoplankton at low nutrient levels to a strong preference for parasitic fungi at high nutrient levels. The model predicts that parasitic fungi could contribute up to 50% of the zooplankton diet in nutrient‐rich environments, which agrees with empirical observations on zooplankton gut content from eutrophic systems during blooms of inedible diatoms or cyanobacteria. Our findings highlight the role of parasite‐mediated energy pathways for predictions of energy flow and community composition under current and future environmental change. [ABSTRACT FROM AUTHOR]

Quantifying the trophic basis of production for freshwater metazoa at broad spatial scales is key to understanding ecosystem function and has been a research priority for decades. However, previous lotic food web studies have been limited by geographic coverage or methodological constraints. We used compound‐specific stable carbon isotope analysis of amino acids (AAs) to estimate basal resource contributions to fish consumers in streams spanning grassland, montane and semi‐arid ecoregions of the temperate steppe biome on two continents. Across a range of stream sizes and light regimes, we found consistent trophic importance of aquatic resources. Essential AAs of heterotrophic microbial origin generally provided secondary support for fishes, while terrestrial carbon did not seem to provide significant, direct support. These findings provide strong evidence for the dominant contribution of carbon to higher‐order consumers by aquatic autochthonous resources (primarily) and heterotrophic microbial communities (secondarily) in temperate steppe streams. [ABSTRACT FROM AUTHOR]

Background: During wastewater treatment, the wastewater microbiome facilitates the degradation of organic matter, reduction of nutrients, and removal of gut parasites. While the latter function is essential to minimize public health risks, the range of parasites involved and how they are removed is still poorly understood. Results: Using shotgun metagenomic (DNA) and metatranscriptomic (RNA) sequencing data from ten wastewater treatment plants in Switzerland, we were able to assess the entire wastewater microbiome, including the often neglected microeukaryotes (protists). In the latter group, we found a surprising richness and relative abundance of active parasites, particularly in the inflow. Using network analysis, we tracked these taxa across the various treatment compartments and linked their removal to trophic interactions. Conclusions: Our results indicate that the combination of DNA and RNA data is essential for assessing the full spectrum of taxa present in wastewater. In particular, we shed light on an important but poorly understood function of wastewater treatment – parasite removal. 6ehe_ZkZdE9fr2WhScWVWR Video Abstract [ABSTRACT FROM AUTHOR]

The human transport and subsequent naturalization of species outside their natural ranges has led to novel interactions between introduced and native species throughout the world. Understanding how introduced species impact pollination networks is useful for both invasive species management and native species conservation and restoration. Banana poka (Passiflora tarminiana), a hummingbird pollinated liana native to South America, has naturalized in higher elevation forests on the islands of Kauaʻi, Maui and Hawaiʻi in the Hawaiian archipelago, habitats in which endemic honeycreepers still occur. To develop an understanding of the interaction between banana poka and honeycreepers, we undertook a floral visitation study at Hakalau Forest National Wildlife Refuge on the island of Hawaiʻi where three nectivorous honeycreepers and banana poka co-occur. Two honeycreeper species, ʻiʻiwi (Drepanis coccinea) and Hawaiʻi ʻamakihi (Chlorodrepanis virens), nectar robbed all of the banana poka flowers that they visited, ostensibly due to the length of the corolla tubes (60–90 mm long) which physically inhibits both honeycreeper species from accessing nectar via the mouth of the corolla. In addition, the standing crop and sugar composition of banana poka floral nectar were assessed. Flowers produced large standing crops (375 ± 132 μL) of nectar containing 29.1 ± 1% (w/v) of sugar that was sucrose-dominant (mean: 95.6 ± 0.5% sucrose in each sample). Our observations suggest that the floral nectar of banana poka may form a substantial component of the diet of both honeycreeper species at the study site. Further research is needed to understand how infestations of banana poka affect bird pollination networks at this and other sites in Hawaiʻi.

We investigated trophic structures in rocky subtidal ecosystems transitioning from canopy-forming to barren states across coastlines with varying oceanographic conditions. We examined stable isotopes and functional traits of common invertebrate and fish taxa to understand the food-web consequences. We hypothesized that resource exploitation patterns of functional guilds would result in distinct isotopic niches, defining trophic diversity and niche. δ13C and δ15N ranges of invertebrate functional groups differentiated pelagic from benthic trophic pathways, reflecting flexible dietary use in the absence of macroalgae. Fish production relied on prey using pelagic and benthic basal resources. Trophic redundancy among consumers within functional guilds contributed to intrinsic trophic structure in barren ecosystems. The resulting community-wide trophic diversity has led to consistent niche widths and overlapping niche space. Overall, our findings highlight the crucial roles of consumers that persist with diverse functional guilds in conferring the adaptability of barren rocky ecosystems following habitat disturbance. • Trophic structures of food webs in coralline-barren rocky ecosystems were investigated. • Invertebrate groups' δ13C and δ15N ranges distinguish pelagic vs. benthic trophic pathways. • Fish production relied on prey using pelagic and benthic basal resources. • Redundant trophic roles within functional guilds shape intrinsic trophic structure. • Community-wide trophic diversity yields consistent niche widths and overlapping space. [ABSTRACT FROM AUTHOR]

Large marine protected areas (MPAs) will likely multiply worldwide to address accelerating biodiversity loss. Coral reefs are an especially at-risk ecosystem, but our understanding of whether and how large MPAs will benefit reef recovery from disturbances remains limited. Here, we evaluate how fishes influence coral reef recovery and if there are cascading trophic interactions in the fish community that influence recovery. We combine i) a meta-analysis of previous research evaluating how fishes affect coral reef succession, ii) field surveys of sharks, fishes, and benthic cover, and iii) a 2.5-year coral recruitment experiment of caged, uncaged, and partially caged settlement tiles in a remote and large MPA, in the Chagos Archipelago. In both our meta-analysis and field experiment, we found variable effects of fishes on coral recruitment with no overall significant effect, but strong control by fishes on the developing benthic communities, where fishes promote crustose coralline algae and reduce macroalgae. Within the Chagos, fishes had a positive effect on corals in protected microhabitats but a negative effect on exposed surfaces, leading to an overall neutral effect from fishes. Although mesopredatory fish abundance was negatively correlated with shark abundance, these top-down effects did not cascade down the food web through herbivores and corallivores to coral recruitment and benthic succession. Thus, our results suggest that within this large MPA, herbivores are important in limiting algae during recovery and there are compensatory responses to the loss of benthic feeding fishes and sharks, with implications for coral reef persistence in the face of global change. [ABSTRACT FROM AUTHOR]

• shifts in abiotic parameters can affect the structure and function of ecosystems. • Ecological network analysis lacks the ability to resolve these dynamic shifts. • new method "Flipbook-ENA" allows an approximation of corresponding system responses. • it provides a quantitative assessment basis for socio-balanced ecosystem management. Changes in abiotic parameters can affect ecosystem structure and function. Network models with subsequent Ecological Network Analysis (ENA) are often used for the quantification of ecosystem-wide properties with descriptive system indices. However, dynamic abiotic alterations of an ecosystem cannot be resolved with the "state of the art" ENA as the methodology of analyses is static in both space and time. In this study, we present a new, almost dynamic ENA "Flipbook-ENA" which allows for the trend analysis of system indices over a defined range of abiotic factors. Flipbook-ENA enables an approximation of the dynamic system response by discretizing the continuous influence of abiotic factors and by calculating the corresponding changes in the model for each discretization step. ENA indices are therefore obtained as a discrete function of the abiotic conditions. We applied this new concept to two aquatic food web models as case studies, using temperature as the influencing abiotic factor. Flipbook-ENA can be considered an enhancement of ENA flexibility, also facilitating the provision of a quantitative assessment basis for socially, economically and ecologically-balanced management of ecosystems in unstable environmental conditions under the pressure of climate change. [ABSTRACT FROM AUTHOR]

This study estimated the accumulation potential of tritium, a major radionuclide released from the Fukushima Daiichi Nuclear Power Station (FDNPS), into the olive flounder as organically bound tritium (OBT) using a computer simulation model. In this estimation, two transfer pathways into the OBT were assumed: formation from tritiated water (HTO) in the tricarboxylic acid (TCA) cycle, and ingestion of OBT through the food chain (from phytoplankton, small fish, to the flounder). The food chain structure was reconstructed based on fish growth model. The OBT concentration in the flounder was estimated on three scenarios: Tritium was supplied to the flounder as only HTO in seawater (Scenario 1), as HTO in seawater and OBT formed from HTO in the small fish (Scenario 2), and as HTO in seawater and OBT accumulated in the small fish through the formation and ingestion of OBT in phytoplankton (Scenario 3). The estimated OBT concentrations in the flounder were in the following order: Scenario 3 > 2 > 1. The ratio of the estimated concentration in Scenario 1 to that in Scenario 3 reached a certain value (66 % after a year from the start of HTO exposure), indicating that the tritium transfer from the seawater into the flounder more significantly contributed to this concentration than ingestions of the small fish and the phytoplankton. Additionally, the difference between the estimations of Scenarios 1 and 2 is significantly larger than that between Scenarios 2 and 3. This suggests that phytoplankton contributed weakly to the OBT concentration in the flounder compared to the small fish. [Display omitted] • 3H accumulation potential into flounder in Japanese coast was estimated. • Tritiated water highly contributed to the accumulation than feed. • Small fish fed by flounder had higher contribution than plankton to the accumulation. • Food web process was suggested to have a significant contribution to the accumulation. • Radiation dose through ingestion of the 3H-contaminated fish was estimated to be small. [ABSTRACT FROM AUTHOR]

Ocean acidification (OA) is known to influence biological and ecological processes, mainly focusing on its impacts on single species, but little has been documented on how OA may alter plankton community interactions. Here, we conducted a mesocosm experiment with ambient (∼410 ppmv) and high (1000 ppmv) CO 2 concentrations in a subtropical eutrophic region of the East China Sea and examined the community dynamics of microeukaryotes, bacterioplankton and microeukaryote-attached bacteria in the enclosed coastal seawater. The OA treatment with elevated CO 2 affected taxa as the phytoplankton bloom stages progressed, with a 72.89% decrease in relative abundance of the protist Cercozoa on day 10 and a 322% increase in relative abundance of Stramenopile dominated by diatoms, accompanied by a 29.54% decrease in relative abundance of attached Alphaproteobacteria on day 28. Our study revealed that protozoans with different prey preferences had differing sensitivity to high CO 2 , and attached bacteria were more significantly affected by high CO 2 compared to bacterioplankton. Our findings indicate that high CO 2 changed the co-occurrence network complexity and stability of microeukaryotes more than those of bacteria. Furthermore, high CO 2 was found to alter the proportions of potential interactions between phytoplankton and their predators, as well as microeukaryotes and their attached bacteria in the networks. The changes in the relative abundances and interactions of microeukaryotes between their predators in response to high CO 2 revealed in our study suggest that high CO 2 may have profound impacts on marine food webs. • The communities were strongly affected by phytoplankton bloom stages. • Ocean acidification (OA) affected some taxa as the phytoplankton bloom stages progressed. • OA changed the co-occurrence network complexity and stability of microeukaryotes. • OA altered the proportions of potential interactions between phytoplankton and their predators. [ABSTRACT FROM AUTHOR]

• Compound-specific isotope analysis of amino acids is an exponentially growing field. • CSIA-AA method use relates more to analyst geography than experimental application. • Optimizing laboratory and instrument methods alike can increase overall data quality. • Method standardization will enhance data accuracy, precision, and reproducibility. Compound specific stable isotope analysis of amino acids (CSIA-AA) is a practice that allows for in-depth studies of many different physiological, ecological, and environmental phenomena. The vast information obtainable through CSIA-AA has driven the exponential growth of this field since its mainstream introduction in the early 1990s. This growth, however, has been accompanied by the development of several distinct analytical approaches. Throughout this review, we outline the full CSIA-AA process and identify areas of its workflow with the highest potential to introduce measurement error. Through a meta-analysis of CSIA-AA publications, we found that rather than experimental application, the primary determinant of methodology lies in the geographic location of the analyst, likely reflective of the academic lineages of CSIA-AA practitioners as opposed to application specific method development. The relative nascency of amino acid isotope analysis gives it incredible expansion potential, but such expansion would greatly benefit from comprehensive experimentation optimizing every portion of the analytical process. While such optimization will require expertise across many areas (i.e., chemistry, mass spectrometry, and data science), uniform guidelines can ensure the highest achievable accuracy and precision for intra- and interlaboratory analyses, alike. The goal of this review is to improve data comparability and adopt standardized methodologies to uniformly generate highly accurate, precise, and reproducible data. In doing so, we make recommendations for areas that would benefit from further investigation (e.g., procedure optimization, error mitigation, and data handling methods). The creation and implementation of guidelines for optimal approaches to CSIA-AA – as has been done for applications like forensic science – can help realize the full potential of this rapidly growing field. [ABSTRACT FROM AUTHOR]

This study evaluates the use of mercury (Hg) concentrations in fish muscle tissue to determine a species’ trophic position (TP) in its environment. A campaign conducted in 2019 along 375 km in the middle Araguaia River basin, Brazil, resulted in 239 organisms from 20 species collected. The highest total mercury (THg) concentrations were found in Pellonacastelnaeana (6.93 µg·g−1, wet weight) and in Triportheus elongatus (3.18 µg·g−1, wet weight), whose TPs were different according to the FishBase database. However, they occupied the same trophic level in this study. The intra-specific comparison showed a difference in Hg concentrations between individuals captured in distinct sites. The study of the biota–sediment accumulation factor (BSAF) showed that spatiality interferes with a species’ TP. Statistical analyses revealed that when we used a predicted species’ TP based on each individual’s size, it explained 72% of the variability in THg concentration across all fish species. Multiple regression analysis confirmed that standard length and FishBase values are positively associated with THg (R2 = 0.943). These results point to Hg as a viable indicator of a fish species’ TP since it reflects regional, biological, and environmental factors, as demonstrated here for the middle Araguaia River.

In the present study, we estimated the levels of infestation of the main fish species that are hosts for two Triaenophorus species: T. crassus and T. nodulosus. The prevalence of T. crassus and T. nodulosus infestations in the intestine of their definitive host–pike Esox lucius was similar (71.0% and 77.4%, respectively). At the same time, the prevalence of T. crassus infestation in muscle tissue was significantly different between the second intermediate hosts, Coregonus lavaretus pidschian (31.4%) and Cor. l. pravdinellus (91.2%), due to considerable differences in their diets. For T. nodulosus, we found significant variations in the levels of prevalence among the second intermediate hosts—100% for Lota lota, 81.8% for Cottus sibiricus 31.9% for Thymallus arcticus, and 24.5% for Perca fluviatilis—that we also explained using different diets. Moreover, analysis of the symmetry of parasite infestations did not reveal any asymmetry between the number of cysts in the left and right body surfaces of the “planktivorous” form/species of whitefish, whereas in the ‘‘benthivorous”, an asymmetry of parasite infestations was found.

Cropland ecosystem functioning may be affected by human perturbations transmitted from adjacent ecosystems, such as freshwater systems. However, our limited knowledge of the ecological interactions within cropland–freshwater networks hinders projecting the consequences of anthropogenic pressures. We reviewed the information from freshwater and cropland communities in the Mediterranean zone of Chile and constructed an ecological metanetwork for characterizing the structure and projecting responses of this system facing environmental pressures. We performed a semi-qualitative analysis to identify the nodes that strongly influence other network components and (or) could significantly affect the transmission of effects within the system. Our analyses show that omnivore fish, amphibians, annual pollinated crops, and deciduous orchards are the most important groups. Although we expected that amphibious predators were the most important groups in transmitting perturbations between ecosystems, we also found groups of plants and pollinators performing this function. We stress that the fate of crop systems facing environmental disturbances should be assessed in a broader context rather than as an isolated system.

Abstract Background During wastewater treatment, the wastewater microbiome facilitates the degradation of organic matter, reduction of nutrients, and removal of gut parasites. While the latter function is essential to minimize public health risks, the range of parasites involved and how they are removed is still poorly understood. Results Using shotgun metagenomic (DNA) and metatranscriptomic (RNA) sequencing data from ten wastewater treatment plants in Switzerland, we were able to assess the entire wastewater microbiome, including the often neglected microeukaryotes (protists). In the latter group, we found a surprising richness and relative abundance of active parasites, particularly in the inflow. Using network analysis, we tracked these taxa across the various treatment compartments and linked their removal to trophic interactions. Conclusions Our results indicate that the combination of DNA and RNA data is essential for assessing the full spectrum of taxa present in wastewater. In particular, we shed light on an important but poorly understood function of wastewater treatment – parasite removal. Video Abstract

Abstract Morphological identification of digested prey remains from a generalist predator can be challenging, especially when attempting to match degraded remains to taxonomic keys. DNA techniques, whereby prey is sequenced and matched to large public nucleotide sequence databases, are increasingly being used to augment morphological identification. We used “metaBARFcoding” (DNA metabarcoding) to target a region of the cytochrome c oxidase subunit I (COI) mitochondrial gene to identify prey in highly digested regurgitations from Christmas shearwaters Puffinus nativitatis at Hōlanikū (Kure Atoll). Metabarcoding was used to bulk‐process 92 water samples from regurgitations collected from 2009 to 2017, providing an overview of the seabird's diet. We additionally Sanger‐sequenced 100 prey items from 50 randomly chosen regurgitations to verify that metabarcoding characterized key components of the diet. The metabarcoding technique identified 87 unique taxa from 29 families of fish and squid, spanning diverse taxa, including reef‐associated, pelagic–oceanic, and mesopelagic species. Rare prey (frequency of occurrence ≤5% of samples) constituted 66% of the species richness, demonstrating the highly diverse diet of this generalist predator. Overall, 81% of the families detected in the contemporary diet were previously documented in Christmas shearwater diets from the Northwestern Hawaiian Islands. Our results indicate that metabarcoding the COI region is useful in identifying a wide range of taxa from highly digested regurgitations, thus facilitating this approach to study seabird diets.

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.

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.

IntroductionMesopelagic fishes play a central role in the transfer of energy through open-ocean food webs, particularly in the Southern Ocean where they are both important predators of zooplankton and a key prey group for many higher predators. However, they are notoriously difficult to sample, which has limited our understanding of the bio-physical predictors of their abundance and spatiotemporal variability. Species distribution models can be used to help understand species’ ecological requirements by relating records of their presence or abundance to environmental data.MethodsHere, we used data from Myctobase – a new circumpolar database of mesopelagic fishes – to model patterns in abundance of eight key myctophid species (family Myctophidae) and the genus Bathylagus in the Southern Ocean south of 45°S. We developed species-specific boosted regression tree models to obtain circumpolar predictions of abundance. Average daytime and night-time summer predictions for the period 1997 to 2011 at 0 to 200m depths were generated for each species.ResultsDepth and solar position were important predictors and species were stratified in their depth distribution. For all species, except for G. nicholsi, there was an interaction between depth of capture and solar position, reflecting diel vertical migration. Other important variables included sea surface temperature, dissolved oxygen at 200 m, chlorophyll a, and sea surface height, indicating an association with water mass properties. Circumpolar patterns of abundance varied between species with some displaying affinities for oceanic regions at Antarctic latitudes (e.g., E. antarctica and Bathylagus spp.) or sub-Antarctic latitudes (e.g., K. anderssoni and P. tenisoni); and affinities for shelf regions (e.g., P. boliniand G. nicholsi).DiscussionOur findings suggest that the abundance of mesopelagic fish is influenced by diel vertical migration and meso- and sub-mesoscale oceanographic features, with the Polar Front being a major delimiting feature. Our study showed contrasting patterns in community composition with higher species diversity north of the Polar Front that might be indicative of latitudinal variability in food web structure. Our spatial analysis is an important step toward resolving what determines important habitat for mesopelagic fishes, providing foundational information for understanding shifting food web dynamics into the future.

Abstract Vector‐borne pathogen transmission is shaped by multiple abiotic and biotic factors. Understanding the relative importance of these factors on vector abundance and infection is important for developing vector‐borne disease control strategies. The crown of the Attalea butyracea palm provides a natural arboreal mesocosm suitable for studying how food web relations and microclimate affect Chagas disease vectors of the genus Rhodnius, which feed on vertebrate blood and interact with many vertebrate and invertebrate species, vegetation, and detritus within the palm crown. We performed a cross‐sectional, observational study of A. butyracea crowns using a community ecology network approach to evaluate abiotic and biotic conditions associated with Rhodnius pallescens abundance and infection with Trypanosoma cruzi, the Chagas disease etiologic agent. We collected 1098 R. pallescens from 105 A. butyracea crowns in rural landscapes of Panama. In a palm subset (N = 49), we recorded microclimate and habitat conditions and counted vertebrate and invertebrate species in order to characterize palm crown food webs. We used food web metrics, namely Generality (average number of prey per predator) and Vulnerability (average number of predators per prey) to evaluate associations between palm community trophic structure, vector predators, vector blood meal species composition, vector abundance, and vector T. cruzi infection. Field data analyzed with generalized linear models showed that vector abundance and infection in a given palm crown were influenced by a combination of geographic location, land‐use type, palm crown animal community composition, and microhabitat conditions. Vector abundance was negatively associated with increased overall palm crown community diversity. However, vector abundance was positively associated with the invertebrate predator and mammal community. R. pallescens Vulnerability score, which measures predation pressure on the vector within the palm crown, was positively associated with vector abundance. Vector infection with T. cruzi was positively associated with mammal presence; vectors in palms with mammals were about 25 times more likely to be infected with T. cruzi compared with vectors in palms without mammals. Our findings suggest that a holistic study of food webs and environmental variables at the local scale can provide useful information for vector‐borne disease management across a wide habitat range.

The Sea of Marmara (SoM), without doubt, is one of the most disturbed marine ecosystems of the Mediterranean basin. As a semi-enclosed and a recognized eutrophic basin, it has a unique natural characteristic by permanent stratification at ~25 m depth. The SoM ecosystem is under threat by multiple stressors from excessive nutrient enrichment, overfishing, invasive species, habitat loss to the climate change. Within this study, an assessment on the SoM ecosystem structure and functioning and its changes over time have been achieved. Hence, we firstly evaluate the SoM ecosystem over a period of three decades from the 1990s to the 2010s by using three mass-balance Ecopath models, secondly, we delineate the prevailing ecosystem structure and functioning in each period, thirdly we determine how the fishing impact contributed to the changes in the SoM since the 1990s and finally establish a baseline for the management and future studies of the ecosystem. The comparison of the models’ results for three consecutive time periods of the SoM showed that the energetic capacity of the ecosystem decreased significantly over the three decades while the decrease in cycling indices indicated that the SoM ecosystem became fragile to anthropogenic disturbances. According to ecosystem theory indices, the SoM is an immature ecosystem at a stage of autotrophic succession, with a very high total primary production, much more above unity that greatly exceeds total respiration. Our results highlighted that the SoM ecosystem was under bottom-up control exerted by mesozooplankton; however, anchovy was a bottleneck in energy transfers to higher trophic levels creating also a wasp-waist control in the food-web. The bycatch of demersal species with long life span, sharks and rays, brought them to the brink of going commercial extinction. Overall, the changes in the SoM ecosystem were due to the trophic cascades exerted by fisheries exploitation in addition to the changes in the productivity of the system. We conclude that the concomitant impacts of stressors on the SoM have been so diverse that an immediate action plan is required. Therefore, we propose a tentative outlook that will help in ecosystem monitoring and better management of the SoM.

Abstract Hemidactylus mabouia is one of the most successful, widespread invasive reptile species and has become ubiquitous across tropical urban settings in the Western Hemisphere. Its ability to thrive in close proximity to humans has been linked to the rapid disappearance of native geckos. However, aspects of Hemidactylus mabouia natural history and ecomorphology, often assumed to be linked with this effect on native populations, remain understudied or untested. Here, we combine data from ∂15N and ∂13C stable isotopes, stomach contents, and morphometric analyses of traits associated with feeding and locomotion to test alternate hypotheses of displacement between H. mabouia and a native gecko, Phyllodactylus martini, on the island of Curaçao. We demonstrate substantial overlap of invertebrate prey resources between the species, with H. mabouia stomachs containing larger arthropod prey as well as vertebrate prey. We additionally show that H. mabouia possesses several morphological advantages, including larger sizes in feeding‐associated traits and limb proportions that could offer a propulsive locomotor advantage on vertical surfaces. Together, these findings provide the first support for the hypotheses that invasive H. mabouia and native P. martini overlap in prey resources and that H. mabouia possess ecomorphological advantages over P. martini. This work provides critical context for follow‐up studies of H. mabouia and P. martini natural history and direct behavioral experiments that may ultimately illuminate the mechanisms underlying displacement on this island and act as a potential model for other systems with Hemidactylus mabouia invasions.

Abstract The utilization of food resources by aquatic consumers reflects the structure and functioning of river food webs. In lotic water systems, where food availability and predator–prey relationships vary with gradient changes in physical conditions, understanding diet assimilation by local communities is important for ecosystem conservation. In the subtropical Liuxi River, southern China, the relative contribution of basal resources to the diet assimilation of functional feeding groups (FFGs) was determined by stable carbon (13C) and nitrogen (15N) isotope analyses. The output of Bayesian mixing models showed that diatom‐dominated periphyton (epilithic biofilm), aquatic C3 plants (submerged hydrophytes), and suspended particulate organic matter (SPOM) associated with terrestrial C3 plants contributed the most to the diet assimilation of FFGs in the upper, middle, and lower reaches, respectively. The relative contribution of consumer diet assimilation was weighted by the biomass (wet weight, g/m2) of each FFG to reflect resource utilization at the assemblage level. From the upper to the lower reaches, the spatial variation in the diet assimilation of fish and invertebrate assemblages could be summarized as a longitudinal decrease in periphyton (from 57%–76% to

Knowledge of in situ diet of widespread rotifers is crucial for accurately understanding the trophic position, ecological function, and adaptability to environmental changes in aquatic ecosystems. However, it is challenging to achieve the in situ diet information due to the lack of efficient and comprehensive methods. Here, we investigated the diet composition of Polyarthra in a subtropical lake using high-throughput sequencing (HTS) of a rRNA metabarcode for Polyarthra and ambient water samples. After eliminating Polyarthra sequences, a total of 159 operational taxonomic units (OTUs) from taxa in 15 phyla were detected from Polyarthra gut content samples. Most of the OTUs belong to Chlorophyta, followed by unclassified Fungi, Chrysophyta, Dinoflagellata, Ciliophora, Bacillariophyta, Cryptophyta, Arthropoda, Cercozoa, Mollusca, Apicomplexa, Haptophyta, Amoebozoa, Chordata and other eukaryotes. Our results showed that Polyarthra mainly grazed on Chlorophyta, which may result from the high relative abundance of Chlorophyta in ambient waters. In contrast, Chrysophyceae and Synurophyceae were enriched in Polyarthra’s gut, indicating that this rotifer prefers these taxa as food. Moreover, correlation analysis showed that total nitrogen, transparency, depth, Chlorophyll-a and total phosphorus were key factors for the variation of the eukaryotic community in the Polyarthra gut contents. When the concentration of nutrients in the water environment decreased, Polyarthra shifted from herbivorous feeding to more carnivorous feeding. Thus, Polyarthra is generally omnivorous but preference for Chrysophytes and Synurophytes, and it responds to the environmental changes by adopting a flexible feeding strategy. This could partly explain why the widespread rotifers have apparently wide tolerance toward spatial and environmental changes.

Anthropogenic climate change is causing changes to the Arctic sea-ice system with implications for the magnitude and timing of Arctic pelagic and ice-associated (sympagic) primary production that influences food web interactions. Ringed seals (Pusa hispida) are generalist predators that, as a species experience vastly different icescapes from low to high-Arctic latitudes. Quantifying spatial variation in their diet can help us understand how changes in sea-ice dynamics affect trophic interactions in Arctic marine food webs. However, multiple complementary analytical tools to examine variation in carbon source use and trophic dynamics in the diet of ringed seals have not yet been applied across their latitudinal range in the Arctic. We conducted stable isotope analysis (δ13C and δ15N) and measured highly branched isoprenoid diatom lipid biomarkers of ringed seals from the low, intermediate, and high Arctic (from 61.1°N to 77.5°N) to investigate spatial variation in their carbon source use and trophic position in relation to sea-ice dynamics. Both δ13C and highly branched isoprenoids indicated that ringed seals from higher latitudes had more sympagic carbon in their diet (liver δ13C: −18.3 ± 0.2 ‰, HBI: 89.9 ± 2.08 %) than ringed seals at lower latitudes (liver δ13C: −21.1 ± 0.1 ‰, HBI: 22.0 ± 2.73 %). Ringed seal trophic position increased from the low (3.78 ± 0.02) to high (4.76 ± 0.03) Arctic, suggesting increased fish consumption or a different trophic structure coinciding with the latitudinal change in carbon source. Ringed seals demonstrated a clear shift from low to high Arctic in the relative contribution of phytoplanktonic vs sympagic primary production. These patterns are likely linked to the vastly different icescapes in these environments and demonstrate that shifts in primary producer composition and Arctic food webs can be identified in ringed seal diets. Information on these prey and energy shifts over large spatial scales also provides insights into potential future changes to Arctic ecosystem function with continued sea-ice decline.

Cross-boundary movements of organisms can act as important ecosystem linkages by subsidizing food webs. We investigated the magnitude and implications of a little understood food web subsidy in the form of migrating aquatic insects, corixids (Hemiptera: Corixidae), that fly from geographically isolated wetlands into large rivers in the Prairie Pothole Region (PPR) of North America every fall, to overwinter. We found that these migrations can lead to drastically increased riverine corixid densities as high as ~ 3,000 individuals/m2 within areas of standing or slow-moving water, with ~ 500 g of corixid material entering every meter of water immediately adjacent to the banks of rivers, where landings are concentrated. This movement shifts the species assemblage in rivers to one dominated by wetland-breeding species, namely Callicorixa audeni, Sigara bicoloripennis, and Sigara decoratella. Stomach content analyses of fish reveal that goldeye (Hiodon alosoides), mooneye (Hiodon tergisus), longnose sucker (Catostomus catostomus), and white sucker (Catostomus commersoni) make heavy use of this forage subsidy, with corixids occurring in 97% to 100% of these fishes and accounting for 38% to 97% of stomach contents by weight during the corixid migration period in fall. We estimate that seasonal migrations could result in ~ 1500 metric tons of corixids entering the North and South Saskatchewan rivers within Saskatchewan, and ~ 12,000 tons of biomass moving between wetlands and rivers across the entire PPR. Our study has demonstrated an extensive cross-boundary flux that occurs between spatially separated wetland and river ecosystems, highlighting a need for conservation to ensure that this connection is maintained. [ABSTRACT FROM AUTHOR]

Predators drive trophic cascades by reducing prey biomass and altering prey traits, selecting for prey that exhibit constitutive and induced anti‐predator defenses that decrease susceptibility to consumption. These defense traits are often costly, generating a tradeoff between consumptive (CEs) and non‐consumptive predator effects (NCEs). The ecological and evolutionary experience that prey share with a given predator may determine their position along this tradeoff curve, affecting the nature and strength of top–down control of ecosystems. Conceptual models predict that predator‐experienced prey suffer greater NCEs than predator–naive prey, which suffer stronger CEs and total predator effects (CEs + NCEs), but this has not been tested in diverse prey communities. We tested these predictions by comparing the effects of predation (CEs + NCEs) and predation risk (NCEs only) of planktivorous fish on food web structure in pond mesocosms with diverse natural communities of either predator‐naive or predator‐experienced zooplankton. Contrary to expectations, top–down control of zooplankton and phytoplankton biomass was strengthened by prey community experience: in systems with experienced relative to naive zooplankton communities both predation risk (NCEs only) and predation (CEs + NCEs) had stronger effects on zooplankton prey biomass and trophic cascades were twice as strong. These results show that the ecological and evolutionary experience of diverse prey communities alters the balance of consumptive and non‐consumptive predator effects and influences trophic cascade strength. [ABSTRACT FROM AUTHOR]

Energy sources and trophic interactions among vent fauna were investigated in deep-sea hydrothermal vents in the North Fiji Basin (NFB), Southwest Pacific, using stable sulfur, carbon, and nitrogen isotopes. A Bayesian isotope mixing model (MixSIAR) was used to quantify the proportions of energy sources for symbiont-bearing taxa. Based on these results, symbionts of host taxa such as the hairy snail Alviniconcha boucheti, black snail Ifremeria nautilei, and vent mussel Bathymodiolus sp. showed different carbon fixation pathways or nutrient preferences. We also observed niche partitioning among the omnivores by utilizing different resources or by occupying different microhabitats. For example, the squat lobster Munidopsis spp. occupied the bottom part of the chimney where dead shells were scattered around, as it was predatory to mussels. The scale worm Branchinotogluma segonzaci exploited energy from particulate organic matter or free-living bacteria on the chimney, whereas shrimp Rimicaris variabilis, which were clustered around I. nautilei and Echionelamus ohtai communities, had isotopic compositions similar to them. In contrast, limpets attached to I. nautilei did not share resources with snails and derived energy from mixed carbon sources. Among the vent fauna that we sampled, the crab was the top predator in the NFB, possibly consuming everything but with a lower preference for mussels. Overall, we found a non-overlapping diet or spatial niche of the vent fauna, with each taxon having a unique source or metabolism, or proportion. Such diversification in resource use may play an important role in sustaining the coexistence of species in a small area. [ABSTRACT FROM AUTHOR]

Stable isotope analysis is ubiquitous as a method to investigate food-web dynamics at various scales in aquatic ecology. Most studies make use of dorsal muscle tissue, which involves lethal sampling of the fish. The sampling of muscle tissue is often followed by chemical lipid extraction pre-treatment before stable isotope analysis. In this study we tested whether stable light isotope results obtained from fin tissue were comparable to those from muscle, and we investigated whether lipid correction could be used as a substitute for lipid extraction. Various lipid correction equations were evaluated. Based on our results, we propose ethical and efficient methods of sample collection and preparation for stable isotope analysis of freshwater fish. We found that dorsal muscle and fin tissue samples could yield similar interpretations of freshwater food-web dynamics in South Africa, demonstrating that fin clippings might be more widely applied as a nonlethal sampling method for stable isotope studies. Existing lipid correction equations either over- or underestimated true lipid extracted δ13C values, therefore an amended lipid correction equation is proposed as it was successfully tested against a population of wild fish. The errors arising from existing lipid correction equations suggest that site-specific calibration should be employed. [ABSTRACT FROM AUTHOR]

Plant quantity and quality can independently affect the diversity of the entire arthropod communities and multiple arthropod taxa in grassland ecosystems. However, it remains unclear how these effects on arthropod taxa at one trophic level propagate through food web to influence the diversity of higher trophic levels.We performed a monoculture experiment with 15 herbaceous species in the Inner Mongolian grassland to investigate how natural variations in plant productivity and host leaf traits affect herbivore taxon richness, which, in turn, affects predator taxon richness.For herbivores, plant productivity indirectly promoted herbivore taxon richness by increasing herbivore biomass, which was attributed to the increases in the richness of dominant sucking herbivores and endophytes with high food requirements. However, the high plant quality indicator (e.g. high leaf protein, phosphorus and water contents, and high leaf protein to carbohydrate ratio) directly increased, whereas the low plant quality indicator (e.g. high leaf lignin content) directly decreased herbivore taxon richness. Taxon richness of chewing and sucking herbivores with specific feeding modes (tearing or sucking mouthparts) showed strong positive responses to increasing plant quality.For predators, herbivore taxon richness, rather than herbivore biomass, mainly mediated the positive effects of plant productivity and the high plant quality indicator, but the negative effect of the low plant quality indicator, on predator taxon richness. At the feeding guild level, the taxon richness of parasitoids, other predators and spiders exhibited positive responses to different herbivores, which was attributed to their different diet preferences. Predator diversity could be promoted by prey partitioning among predator guilds facilitating species coexistence. At the family level, the taxon richness of most predator families was positively correlated with that of more than one herbivore family, suggesting that high predator diversity may be caused by balanced diets owing to high prey diversity.Synthesis. Natural variations in plant quantity and quality can substantially affect the diversity of herbivores and cascade up the food web to affect predators. Specificity and mechanisms of feeding have a large impact on the responses of arthropod guilds at each trophic level. [ABSTRACT FROM AUTHOR]

Resolving the combined effect of climate warming and exploitation in a food web context is key for predicting future biomass production, size‐structure and potential yields of marine fishes. Previous studies based on mechanistic size‐based food web models have found that bottom‐up processes are important drivers of size‐structure and fisheries yield in changing climates. However, we know less about the joint effects of 'bottom‐up' and physiological effects of temperature; how do temperature effects propagate from individual‐level physiology through food webs and alter the size‐structure of exploited species in a community? Here, we assess how a species‐resolved size‐based food web is affected by warming through both these pathways and by exploitation. We parameterize a dynamic size spectrum food web model inspired by the offshore Baltic Sea food web, and investigate how individual growth rates, size‐structure, and relative abundances of species and yields are affected by warming. The magnitude of warming is based on projections by the regional coupled model system RCA4‐NEMO and the RCP 8.5 emission scenario, and we evaluate different scenarios of temperature dependence on fish physiology and resource productivity. When accounting for temperature‐effects on physiology in addition to on basal productivity, projected size‐at‐age in 2050 increases on average for all fish species, mainly for young fish, compared to scenarios without warming. In contrast, size‐at‐age decreases when temperature affects resource dynamics only, and the decline is largest for young fish. Faster growth rates due to warming, however, do not always translate to larger yields, as lower resource carrying capacities with increasing temperature tend to result in decline in the abundance of larger fish and hence spawning stock biomass. These results suggest that to understand how global warming affects the size structure of fish communities, both direct metabolic effects and indirect effects of temperature via basal resources must be accounted for. [ABSTRACT FROM AUTHOR]

A review of the published literature on the trophic magnification factor (TMF) for per‐ and polyfluoroalkyl substances (PFAS) was conducted to assess how biomagnification varies across aquatic systems worldwide. Although the TMF has been recognized as the most reliable tool for assessing the biomagnification of organic contaminants, peer‐reviewed studies reporting TMFs for PFAS are few and with limited geographical distribution. We found 25 published studies of the biomagnification of 35 specific PFAS, for which the TMF was generated through linear regression of individual log‐PFAS concentration and the δ15N‐based trophic position of each organism in the food webs. Studies were concentrated mainly in China, North America, and Europe, and the most investigated compound was perfluorooctane sulfonate (PFOS), which was frequently shown to be biomagnified in the food web (TMFs ranging from 0.8 to 20). Other long‐chain carboxylates displayed substantial variation in trophic magnification. Observed differences in the TMF were associated with length of the food web, geographic location, sampling methodologies, tissue analyzed, and distance from known direct PFAS inputs. In addition to biomagnification of legacy PFAS, precursor substances were observed to bioaccumulate in the food web, which suggests they may biotransform to more persistent PFAS compounds in upper trophic levels. This review discusses the variability of environmental characteristics driving PFAS biomagnification in natural ecosystems and highlights the different approaches used by each study, which can make comparisons among studies challenging. Suggestions on how to standardize TMFs for PFAS are also provided in this review. Integr Environ Assess Manag 2022;18:1500–1512. © 2022 SETAC KEY POINTS: Polyfluoroalkyl substances (PFAS) studies using the trophic magnification factor (TMF) were concentrated mainly in China, North America, and Europe.Perfluorooctane sulfonate (PFOS) was the main compound analyzed over the 20 years of international concern regarding its potential to accumulate in biota.Long‐chain PFAS compounds showed considerable variation in their bioaccumulation through the food web, which was associated with differences not only in biological characteristics of the sampled organisms but also in methodologies among studies.The presence of PFAS precursors in the studied environments was highlighted as a potentially important factor in amplifying TMF values for legacy compounds. [ABSTRACT FROM AUTHOR]

Originating from South East Asia the catadromous Chinese mitten crab (Eriocheir sinensis H. Milne Edwards, 1853) is listed as one of the 100 world's worst invasive species. In 1912 E. sinensis was first recorded in Central Europe. Nowadays the species is common in various European rivers and widespread in large rivers of the northern hemisphere. High densities of the crab can cause serious economic damage in water management and to the fishing industry. During their natural migration from the estuary upstream, subadult individuals are able to reach river sections several hundred kilometers away from the delta. The ecological impacts on community and food web structures of the Chinese mitten crab (CMC) are less often considered in scientific studies than their economic effects. The diet of CMC under natural conditions is rarely studied, but macrophytes are known to be an important food source of the crab. However, in the main stretch of the Lower Rhine macrophytes are broadly missing. Initial stable isotope analyses showed that CMC occupies a trophic level comparable to carnivorous fish in this system. Thus, a strong predatory impact of CMC on the fauna is likely. Here we use qualitative and quantitative approaches to investigate the diet of Chinese mitten crab to estimate their impact on the food web. Bulk stable isotope analyses of δ13C and δ15N of E. sinensis and potential food resources were conducted and genetic gut content analyses (GGCA) via group-specific primers for common macroinvertebrates of the River Rhine were used to determine prey organisms. While GGCA only rarely detected invertebrate prey and many plant fibres were visible in the stomachs and guts of the CMCs, stable isotope mixing model (simmr) analyses revealed a high contribution of some easily accessible macroinvertebrate species to the CMCs diet. This contradiction between the gut content findings and the simmr mixing model results indicate not only that animal material is more easily assimilated, but also that the CMC may have a strong impact on the benthic fauna of the Lower Rhine, which would have been underestimated if solely gut content analyses were used. [ABSTRACT FROM AUTHOR]

In order to study the stability of the ecosystem under external attack, we regard the ecosystem as a complex network and the species disturbance after the attack as an infectious disease. We establish an ecological network disturbance propagation model based on the infectious disease model, and analyze its dynamics with the above ideas. In this paper, the species are regarded as nodes in the network, and the predator–prey relationship is regarded as the edge of the network. When the ecosystem is attacked by external forces, the disturbance can be transmitted from a species to its predator or prey through the food chain, and the disturbed species can recover themselves and then return to a stable state. At the same time, we consider adding human quarantine and protection of disturbed species. In this way, all species in the ecosystem are divided into four states: undisturbed, disturbed, quarantine and recovered. By analyzing the dynamics of disturbance propagation, the critical threshold and equilibrium point of disturbance diffusion are determined, and the local and global stability of disease-free equilibrium and endemic equilibrium are analyzed. The results show that the existence of endemic equilibrium depends on the critical threshold of disturbance propagation, which is related to the structure of food web, the propagation proportion of disturbance and the recovery proportion of species after being attacked. The larger the propagation proportion is, the weaker the resistance stability is, and the easier the disturbance propagates in the system. The higher the recovery proportion of the disturbed species, the stronger the stability of the recovery rate, and the more difficult it is for the disturbance to propagate in the system. Then we regard human protection of species as species immunity, and choose the most effective species protection measures by comparing and analyzing the threshold changes under the three protection strategies. The results show that the moderately large neighbor nodes of the disturbed species should be protected. This kind of protection measure is the most effective and it is easier to restrain the propagation of disturbance. Finally, the food webs of 85 species in a pine forest in Otago, New Zealand is selected to analyze the propagation process of disturbance by numerical simulation. [ABSTRACT FROM AUTHOR]

In an era of mass extinction, predicting the consequences of species loss has become a priority for ecologists. Extinction of one species can trigger the loss of dependent species, sometimes leading to cascades of extinctions. Simulations predict that cascading extinctions should be commonplace, but empirical observations of extinction cascades rarely match those predicted by simulation. By contrast, species-removal field experiments have yielded surprises, such as novel interactions following removals. Thus, given this mismatch, the true predictive value of extinction simulation studies is unknown. We explore the value of validating extinction simulations with observational and experimental studies. We propose a new framework that unites both approaches to studying extinction cascades, and which reveals new opportunities to couple theory and data. We are facing many local and global extinction events as part of the sixth global mass extinction. Many studies focus on the extinction risk of individual species, but what are the knock-on effects when the prey of a specialist predator becomes extinct or a plant loses its only pollinator? The potential loss of species and their interactions through coextinction remains difficult to predict, and this obscures our ability to predict extinctions from global change and impacts on ecosystems. Experimental and theoretical studies of coextinction have progressed largely in parallel. Many studies simulate species loss using robustness analysis, whereas relatively few monitor coextinctions in situ following natural species loss or experimental species removal. The combination of theoretical and empirical studies on coextinctions could provide new predictive insights into complex ecosystems. [ABSTRACT FROM AUTHOR]

Incorporating organismal hydrogen (δ2H or δD) and oxygen (δ18O) stable isotope ratios into aquatic food web research can help elucidate relative reliance on shoreline inputs and/or feeding at different trophic levels; however, their interpretation is complicated by the fact that aquatic organisms derive hydrogen and oxygen from both their diet and the ambient water in which they reside. We examined spatial and seasonal patterns in δ2H and δ18O of field-collected water and small-bodied fishes. Samples were gathered from nearshore Lake Michigan, a dynamic region of a large, increasingly oligotrophic freshwater lake. We examined seasonal and spatial δ2H and δ18O values of surface and bottom water, and compared spatial δ2H and δ18O values of young-of-year yellow perch (Perca flavescens) and seasonal δ2H and δ18O values of round goby (Neogobius melanostomus). Nearshore δ2H and δ18O water values were more variable than previously-described offshore values. Variation in nearshore water δ2H and δ18O values was likely related to differential precipitation and/or discharges from tributaries, and there may be a surface dilution effect which led to lower δ18O values in nearshore surface waters than bottom waters. In our study, fish tissue δ2H and δ18O also varies more spatially than seasonally, and some findings suggest that fish tissue δ2H may reflect feeding at higher trophic levels. Though characteristics of the study system affect their interpretation, we suggest that δ2H and δ18O can be another tool to assess food web structure, with δ2H in particular having potential to resolve questions when δ13C or δ15N are inconclusive. [ABSTRACT FROM AUTHOR]

We studied the abundance, biomass and diet of Platevindex aff. tigrinus in the Hara Biosphere Reserve in the Persian Gulf. The seasonal sampling (two seasons) was conducted in winter 2018 and summer 2019. Samples were collected from six sites in Qeshm Island and Bandar Khamir. To determine the effect of environmental parameters on distribution of the species, temperature, salinity, pH, sediment grain size, total nitrogen and organic carbon were measured at each site. The results showed that the abundance of P. tigrinus was significantly higher in the winter compare to summer season. However, there was no significant difference in the biomass of the species between seasons. The PCA results showed that salinity, temperature and sediment grain size contributed to the separation of between seasons. The pH and total nitrogen followed the similar pattern in different sites and seasons. Although, temperature, salinity, sediment grain size, and organic carbon showed difference between seasons. The results showed that salinity and temperature were two important parameters in the distribution of the species during both seasons. The species was mainly feeding on the microphytobenthos during winter and on the sediment organic matter during summer. [ABSTRACT FROM AUTHOR]

Many papers have been published for finding eigenvalues and eigenvectors of a fuzzy matrix (FM) (i.e. matrix with membership values) as well a fuzzy graph. But, all papers determine such parameters based on conventional arithmetic operators, though the valid operations on FMs are max–min. To the best of our knowledge no papers are published to find eigenvalues and eigenvectors based on max–min operators. In this paper, a novel technique is adapted to find the eigenvalues and eigenvectors of an interval-valued fuzzy graph (IVFG) using max–min operators. The energy of an IVFG is defined and computed using max–min operators. Finally, an application of eigenvalues of an IVFG is discussed for the ecological system. In ecology, the amount of food consumed by a predator from the preys is represented as an interval valued fuzzy membership values which is natural as the consumption of food for a predator from preys is uncertain. So this application is very much appropriate for eigenvalues and eigenvectors as well as energy of an IVFG. [ABSTRACT FROM AUTHOR]