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Ecosystems that are coupled by reciprocal flows of energy and nutrient subsidies can be viewed as a single "meta-ecosystem." Despite these connections, the reciprocal flow of subsidies is greatly asymmetrical and seasonally pulsed. Here, we synthesize existing literature on stream-riparian meta-ecosystems to quantify global patterns of the amount of subsidy consumption by organisms, known as "allochthony." These resource flows are important since they can comprise a large portion of consumer diets, but can be disrupted by human modification of streams and riparian zones. Despite asymmetrical subsidy flows, we found stream and riparian consumer allochthony to be equivalent. Although both fish and stream invertebrates rely on seasonally pulsed allochthonous resources, we find allochthony varies seasonally only for fish, being nearly three times greater during the summer and fall than during the winter and spring. We also find that consumer allochthony varies with feeding traits for aquatic invertebrates, fish, and terrestrial arthropods, but not for terrestrial vertebrates. Finally, we find that allochthony varies by climate for aquatic invertebrates, being nearly twice as great in arid climates than in tropical climates, but not for fish. These findings are critical to understanding the consequences of global change, as ecosystem connections are being increasingly disrupted.

The trophic organization of estuarine fish communities is poorly known. We used Stable Isotopes (δ13C and δ15N) to classify the most abundant fishes of the Atrato River Delta (Colombia) into trophic guilds. We examined trophic niches and the relationships between the abundance of the trophic guilds (catch per unit effort) and environmental variables. The zoobenthivores were the dominant trophic guild. The isotopic niche width, based on Bayesian estimate of the standard ellipse areas, was more significant for carnivores (25.3‰2) and planktivores (24.4‰2) than for omnivores (7.8‰2) and phytobenthivores (3.1‰2). The overlap combinations showed a medium probability of isotopic overlap (≈50%) between carnivores and planktivores and between carnivores and omnivores. Isotopic niche size and overlap suggested diversity in food sources and considerable niche segregation of the fish community. Mangrove area was the main factor explaining the abundance of omnivores and zoobenthivores, supporting that the causal links between mangrove habitat and local fishery production may be explained through the trophic contribution of mangroves and mangrove-related sources. The results underscore the importance of mangrove areas in the trophic organization of fish communities and can inform strategies aimed at managing the ecosystem impacts of fishing and protecting extensive mangrove areas in the southern Caribbean. [ABSTRACT FROM AUTHOR]

In addition to considering the influence of a species on other species (centrality), the identification of keystone species should also consider whether it has a unique network position (uniqueness). Clarifying the correlation between species centrality and uniqueness, or whether central species exhibit positional redundancy in food webs, can enhance the understanding of mechanisms stabilizing food webs. However, the findings from analyses utilizing different measures of uniqueness are contentious. In this study, we constructed the food web of the eutrophic Zhangze Lake (northern China) using stable isotopes to estimate the contribution of food sources to consumers. We then calculated trophic field overlap index to assess the uniqueness of species using this quantified food web information. Additionally, we analyzed how the weak interaction and the threshold value under which interactions are considered as weak influence the relationship between species uniqueness and centrality. The findings revealed that, in contrast to the traditional trophic field overlap index, the improved index identified the basal species with the strongest trophic interactions with other species and the filter‐feeding fishes with the fewest interactors as the most unique species, while the basal species were considered the least unique under the traditional index. The ranking results of the traditional index and the centrality showed a significant negative correlation, whereas the improved index displayed a positive correlation, which was caused by the comprehensive consideration of threshold and weak interaction. In addition, based on the data analysis, the suggestion was given for the selection of indices used to identify unique species, and whether central species have positional redundancy was explored. The methodology used in study provides a practical solution for the identification of the most unique species, points out and solves the problems faced in the uniqueness analysis, and advances the understanding of the mechanisms underlying food web robustness. [ABSTRACT FROM AUTHOR]

Glaciers are retreating worldwide at an ever‐increasing rate, exposing new ice‐free areas to ecological succession. This process leads to changes in biodiversity and potentially to novel species interactions. However, we still have a limited understanding of how glacier retreat influences species interaction networks, particularly the structure and robustness of mutualistic networks. After reconstructing plant–pollinator networks along a 140‐years chronosequence on a glacier foreland, we address the effects of glacier retreat on network structure and robustness. Our results show that the prevalence of different network motifs changes over spacetime, leading to a decrease of network robustness. With glacier retreat, mutualistic networks shift from highly connected with diverse specialist interactions to loosely connected with few generalist interactions. Furthermore, despite the turnover of plant species, we find that species structural roles remain constant over spacetime while depending on species identity. Our findings suggest that glacier retreat reshuffles mutualistic networks with motifs posing low robustness, leading to increased fragility. Understanding the assembly and breaking down of species interaction networks provides novel insights into the development and stability of novel, post‐glacial ecological systems facing glacier extinction. [ABSTRACT FROM AUTHOR]

Nitrogen stable isotope ratios (δ15N) are widely used to quantify trophic position in aquatic ecosystems. Comparing trophic position across space requires identifying baselines to account for variation in δ15N values of basal energy resources, but few standardized methods exist for identifying suitable baselines. We evaluated a standardized method for identifying optimal isotopic baselines in streams spanning the Rocky Mountains–Great Plains ecotone. We assessed candidate taxonomic groups and feeding groups following four criteria: (1) Organisms should be easy to collect and widely distributed, (2) Within-site δ15N variation should be low (representative of uniform feeding behavior), (3) δ15N values should be correlated with geographic variability in δ15N values, and (4) Trophic position of consumers calculated using the baseline should be independent of geographic δ15N variability when there is no change in diet. Simuliidae (obligate, sestonic filter feeders) met all four criteria for four fishes and produced trophic position estimates consistent with dietary changes for brown trout along a longitudinal stream gradient. The four-criteria screening method is suitable for temperate streams in North America and supports the recommendation to use Simuliidae or potentially grouped filter feeders as baseline organisms for stable isotope studies quantifying trophic position in higher-order consumers. [ABSTRACT FROM AUTHOR]

Urbanization transforms natural river channels, and surface water of some rivers disappeared over time. How and whether the subsurface domains of the original waterways and aquifers connecting them (a phantom of historical landscape) are functional is not known. This study examined the effects of tributary groundwater inflow on the response of river–riparian organisms in an alluvial mainstem river in northern Japan, where the tributary disappeared over the course of urban landscape transformation.A 2.8‐km lowland segment of the mainstem gravel‐bed river was examined for water properties and the river–riparian food web. In addition, watershed‐wide water sampling was conducted to isotopically distinguish several types of groundwater that contributed to the hyporheic water in the study segment. Altitude had a clear effect on the hydrogen/oxygen stable isotope ratios in the river water collected across the watershed.Groundwater unique both in chemical and isotopic signatures occurred in several spots within the study segment, and its properties resembled and its upwelling locations matched groundwater from a tributary river whose surface channel disappeared 60 years ago. Positive numerical increases in abundance and/or a sign of nitrogen transfer in river–riparian communities (algae, invertebrates and riparian trees) originating from groundwater high in nitrate with elevated nitrogen stable isotope ratios were found.We demonstrated that tributary groundwater with unique chemical properties manifested by an urban watershed river network continued to have trophic effects on biota across the river–riparian boundary in the mainstem river, even after urbanization transformed the tributary into a phantom river. We highlighted the legacy effects of landscape transformation in the subsurface domain and the significance of scrutinizing the past landscape and hydrological connectivity at the watershed scale in urban environments. [ABSTRACT FROM AUTHOR]

Perfluoroalkyl and polyfluoroalkyl substances (PFAS) have been extensively documented as posing significant health risks to human populations. However, there is a lack of research of their impact on endangered species, which significantly affects the effectiveness of conservation efforts and maintenance of these populations. In this study, we examined the levels of PFAS pollution in adults and juveniles of the vulnerable Saunders's gull (Larus saundersi), along with their various food sources using ultra high-performance liquid chromatography-tandem mass spectrometry and Ecopath model. Long-chain PFAS, predominantly composed of perfluorooctanoic acid (accounting for 51.4% of the total), were identified as the main pollutants in the gull, its food, and the environment. Saunders's gulls showed significant bioaccumulation and magnification of PFAS, with contamination levels significantly above those recorded in other species. Mean PFAS levels between juveniles (904.26 ng/g wet weight) and adults (407.40 ng/g wet weight) revealed a significant disparity, indicating that PFAS pollution may severely threaten these birds. Among the food sources analyzed, bivalves and polychaetes emerged as the primary contributors to PFAS contamination in Saunders's gulls, with high transfer efficiency. The fundamental cause of PFAS pollution in benthic organisms and the gulls appears to be baseline environmental pollution, which was highly consistent across all examined pollutant types. Moreover, chemical plants close to breeding areas may cause severe environmental pollution, threatening organisms at various trophic levels through the food web. We suggest enhancing the pollution monitoring of important biological habitats for timely prediction and early warning of chemical risks. Additionally, ecological restoration of key habitats should be strengthened to ensure the effectiveness of biodiversity conservation. [ABSTRACT FROM AUTHOR]

DNA metabarcoding andmorphological taxonomic (microscopic) analysis of the gut contents was used to examine diet diversity of seven species of fishes collected from mesopelagic depths (200-1000 m) in the NW Atlantic Ocean Slope Water during Summer 2018 and 2019. Metabarcoding used two gene regions: V9 hypervariable region of nuclear 18S rRNA and mitochondrial cytochrome oxidase I (COI). V9 sequences were classified into 14 invertebrate prey groups, excluding fish due to predator swamping. Ecological network analysis was used to evaluate relative strengths of predator-prey linkages. Multivariate statistical analysis revealed consistently distinct diets of four fish species in 2018 and/or 2019: Argyropelecus aculeatus, Chauliodus sloani, Hygophum hygomii, and Sigmops elongatus. Three other species analyzed (Malacosteus niger, Nemichthys scolopaceus, and Scopelogadus beanii) showed more variability between sampling years. COI sequences were classified into eight invertebrate prey groups, within which prey species were detected and identified. Considering all predator species together, a total of 77 prey species were detected with a minimum of 1,000 COI sequences, including 22 copepods, 18 euphausiids, and 7 amphipods. Morphological prey counts were classified into seven taxonomic groups, including a gelatinous group comprised of soft-bodied organisms. The ocean twilight zone or is home to exceptional diversity and biomass of marine fish, which are key players in deep sea food webs. This study used integrative morphological-molecular analysis to provide new insights into trophic relationships and sources of productivity for mesopelagic fishes, including identification of key prey species, recognition of the importance of gelatinous prey, and characterization of differences in diet among fish predators in the NW Atlantic Slope Water. [ABSTRACT FROM AUTHOR]

Predators regulate communities through top‐down control in many ecosystems. Because most studies of top‐down control last less than a year and focus on only a subset of the community, they may miss predator effects that manifest at longer timescales or across whole food webs. In southeastern US salt marshes, short‐term and small‐scale experiments indicate that nektonic predators (e.g., blue crab, fish, terrapins) facilitate the foundational grass, Spartina alterniflora, by consuming herbivorous snails and crabs. To test both how nekton affect marsh processes when the entire animal community is present, and how prior results scale over time, we conducted a 3‐year nekton exclusion experiment in a Georgia salt marsh using replicated 19.6 m2 plots. Our nekton exclusions increased densities of plant‐grazing snails and juvenile deposit‐feeding fiddler crab and, in Year 2, reduced predation on tethered juvenile snails, indicating that nektonic predators control these key macroinvertebrates. However, in Year 3, densities of mesopredatory benthic mud crabs increased threefold in nekton exclusions, erasing the tethered snails' predation refuge. Nekton exclusion had no effect on Spartina biomass, likely because the observed mesopredator release suppressed grazing snail densities and elevated densities of fiddler crabs, whose burrowing alleviates soil stresses. Structural equation modeling supported the hypotheses that nektonic predators and mesopredators control invertebrate communities, with nektonic predators having stronger total effects on Spartina than mud crabs by controlling densities of species that both suppress (grazers) and facilitate (fiddler crabs) plant growth. These findings highlight that salt marshes can be resilient to multiyear reductions in nektonic predators if mesopredators are present and that multiple pathways of trophic control manifest in different ways over time to mediate community dynamics. These results highlight that larger scale and longer‐term experiments can illuminate community dynamics not previously understood, even in well‐studied ecosystems such as salt marshes. [ABSTRACT FROM AUTHOR]

Consumers are thought to select food resources based on their nutritional content. While laboratory experiments have explored this, the nutritional dynamics of invertebrate predators have been scarcely studied in the field given various methodological constraints. The intersection of these nutritional dynamics with predator traits is also poorly characterised, leading to many gaps in our understanding of how different predators forage and feed in natural systems. Here, we integrate dietary metabarcoding with prey macronutrient (protein, lipid and carbohydrate) content and abundance to assess how nutrients and predator traits (sex, life stage and taxonomy) interactively drive prey preferences in the field, using spider–prey interactions as a model system. Different spider genera, sexes and life stages had nutritionally distinct diets. Our analyses demonstrated disproportionate foraging (selection and avoidance) for prey rich in different macronutrients, with the nature of these relationships differing between spider taxa, life stages and sexes. This may be explained by niche differentiation among spider groups, driven by biases toward prey rich in different nutrients, or nutrient‐specific foraging in which individual spiders vary their nutritional preferences to redress deficits, although further evidence is required to confirm this. This insight into the nutritional dynamics of generalist invertebrate predators extends our understanding beyond lab‐based behavioural assays and provides a novel framework for other complex real‐world systems. [ABSTRACT FROM AUTHOR]

The aquaculture industry is growing rapidly and plays a huge role in bridging the global demand gap for fish and other aquatic foods. It is a vital contributor of valuable nutrients and economic benefits. Aquaculture and fisheries provide a means of livelihood to an estimated 58.5 million people globally, according to the United Nations Food and Agriculture Organisation. However, the sector is impacted by the ubiquity of microplastics and toxic chemicals. Although many studies have reported plastic pollution in the aquaculture environment, less attention has been paid to the coexistence of toxic chemicals with plastic particles and the role of climate change in aquaculture food contamination. This review evaluates the occurrence of microplastics in organisms, feeds, water, and sediment in the aquaculture ecosystem and the detection and hazardous effects of toxic chemical contaminants. We also highlight novel insights into the role of climate change in plastic and chemical contamination of aquaculture organisms and ecosystems. We report that the extent of aquaculture's contribution to global climate change and global plastic pollution is yet to be adequately quantified and requires further investigation for appropriate risk assessment and prevention of food safety crisis. Possible mitigation strategies for the highlighted pollution problems were suggested, and some identified gaps for future research were indicated. Overall, this work is one of the first efforts to assess the influence of climate change on aquaculture food contamination, emphasising its effects on food safety and ecosystem health. [ABSTRACT FROM AUTHOR]

For many decades, ecologists have sought to understand the extent to which species losses lead to secondary extinctions—that is, the additional loss of species that occurs when resources or key interactions are lost (i.e. robustness). In particular, ecologists aim to identify generalisable rules that explain which types of food webs are more or less robust to secondary extinctions. Food web structure, or the patterns formed by species and their interactions, has been extensively studied as a potential factor that influences robustness to species loss. We systematically reviewed 28 studies to identify the relationships between food web structure and robustness to species loss and how the conclusions depend on methodological differences. Contrary to popular belief and theory, we found relatively consistent, positive relationships between connectance and robustness, among other generalities. Yet, we also found that conflicting conclusions about structure‐robustness relationships can be, in part, attributed to differences in the type of data that studies use, particularly studies that use empirical data versus those generated from theoretical models. This review points towards a need to standardise methodology to answer the open question of whether robustness and its relationship with food web structure and to provide applicable insights for managing complex systems. [ABSTRACT FROM AUTHOR]

Although the transfer of methane‐derived carbon (MDC) to benthic macroinvertebrates such as chironomid larvae and oligochaetes has been well documented, knowledge of the transfer of MDC to fish is limited.We investigated the MDC contribution to 28 fish species through their growth stages and examined the relationship between fish traits including body size, and MDC contribution to fish within species in Lake Kasumigaura, Japan. We used carbon stable isotope ratios and a two‐source mixing model (methane‐oxidation bacteria [MOB] and particulate organic matter) to estimate the MDC contribution to fish.The MDC contribution to individual fish ranged from 0% to 21.5%. Anguilla japonica showed the highest MDC contribution (mean 3.8%). Fish species were classified into four groups according to two criteria: (a) whether the correlation between the MDC contribution and fish size (within species) was significantly negative (negative vs. not significant; ns); and (b) whether the 90th percentile of MDC contribution was 0% or not. The mean MDC contribution was highest (2.18% ± 2.93%, 12 species) for the group with (a)ns/(b)>0%, including the high contribution species such as Abbottina rivularis (mean 5.5%) and Biwia zezera (mean 9.8%). This group (12 species) included relatively high numbers of benthic habitat use (eight species) and omnivores (nine species). The mean MDC contributions were almost zero for the group with (a)ns/(b)=0% (seven species), which included only two species of benthic habitat use and one species of omnivores. The mean MDC contributions were intermediate for the other groups with (a)negative/(b)>0% (1.30% ± 1.17%, seven species) and (a)negative/(b)=0% (0.10%, two species). The negative correlation between fish size within species and MDC contribution in groups with (a)negative/(b)>0% and (a)negative/(b)=0% indicated that ontogenetic habitat and dietary shifts induced changes in MDC transfer.Our results suggest that 21 out of 28 fish species were involved in the MDC transfer in a shallow lake, but variation in MDC transfer could be explained by fish traits (trophic guild and habitat use). Although the mean MDC contribution to all fish species was low (0.61% ± 1.97%), the roughly estimated annual consumption rate of fish on MOB corresponded to approximately 10% of the MOB production in the sediment, suggesting that fish contribute to methane dynamics from the perspective of biogeochemical cycles. [ABSTRACT FROM AUTHOR]

Small pelagic fish (SPF) are crucial in marine food webs, transferring energy from plankton to higher trophic levels. This study focuses on herring (Clupea harengus) and sprat (Sprattus sprattus), addressing knowledge gaps in their feeding ecology in a nursery area, the Dutch Wadden Sea. We conducted a year-long, monthly survey, and used DNA metabarcoding to analyse zooplankton samples and stomach contents of two size classes of herring and sprat. Intra-, interspecific, and seasonal variations in fish condition, stomach fullness, and diet composition, along with selective feeding, were studied. Our study showed that condition and diet composition of herring and sprat, along with zooplankton density, exhibited a clear seasonal pattern. Juvenile herring and sprat displayed opportunistic feeding behaviour, rather than showing distinct prey selection. Besides copepods, we regularly observed (larvae of) benthic invertebrates in their diet. This emphasizes the crucial role of SPF as energy transfer agents, not solely between trophic levels, but also from benthic to pelagic habitats. Furthermore, fish post-larvae were part of the diet of larger herring (10–15 cm). Because of its unprecedented temporal and taxonomical detail, this study advances the understanding of seasonal dynamics of dominant components at the base of the Wadden Sea food web. [ABSTRACT FROM AUTHOR]

Host populations often vary in the magnitude of coinfection they experience across environmental gradients. Furthermore, coinfection often occurs sequentially, with a second parasite infecting the host after the first has established a primary infection. Because the local environment and interactions between coinfecting parasites can both drive patterns of coinfection, it is important to disentangle the relative contributions of environmental factors and within‐host interactions to patterns of coinfection.Here, we develop a conceptual framework and present an empirical case study to disentangle these facets of coinfection. Across multiple lakes, we surveyed populations of five damselfly (host) species and quantified primary parasitism by aquatic, ectoparasitic water mites and secondary parasitism by terrestrial, endoparasitic gregarines. We first asked if coinfection is predicted by abiotic and biotic factors within the local environment, finding that the probability of coinfection decreased for all host species as pH increased. We then asked if primary infection by aquatic water mites mediated the relationship between pH and secondary infection by terrestrial gregarines.Contrary to our expectations, we found no evidence for a water mite‐mediated relationship between pH and gregarines. Instead, the intensity of gregarine infection correlated solely with the local environment, with the magnitude and direction of these relationships varying among environmental predictors.Our findings emphasize the role of the local environment in shaping infection dynamics that set the stage for coinfection. Although we did not detect within‐host interactions, the approach herein can be applied to other systems to elucidate the nature of interactions between hosts and coinfecting parasites within complex ecological communities. [ABSTRACT FROM AUTHOR]

Ecological interactions, such as food webs, are fundamental for predicting ecosystem responses to environmental changes and anthropogenic disturbances. With wetland ecosystems facing escalating threats from intensified land use, our study aimed to assess the effect of land use on macroinvertebrate food webs across four riverine wetlands situated in lowland streams of the Pampean ecoregion in Argentina. Two wetlands were situated in peri-urban agriculture areas, whereas the other two were located in rural areas with extensive livestock. Through macroinvertebrate sampling and gut content analysis, we present a general description of the diet and a classification of species on the basis of the proportion of different food items in their gut contents. Food webs were constructed for each wetland using the gut content data and structural attributes, such as food web size, number, complexity, and density of trophic links among others, were estimated. Our findings reveal that detritus is the primary resource in macroinvertebrate diets across all wetlands, followed by animal and plant remains. Peri-urban agricultural riverine wetlands exhibited simpler food webs compared to the rural ones, with smaller food web size and lower number, density, and complexity of trophic links. Rural wetlands were characterized by a higher degree of omnivory and proportion of top nodes, whereas peri-urban agricultural wetlands presented a higher number of basal nodes and resource: consumer index. These results suggest that land use may affect the structure of macroinvertebrate food webs in riverine wetlands, contributing to a better understanding of the functioning of these valuable ecosystems. [ABSTRACT FROM AUTHOR]

There is increasing adoption of winter cover crops (WCCs) in corn and soybean production in Canada, primarily to reduce erosion and increase soil organic matter content. WCCs have the potential to influence nematode communities by increasing free-living nematodes and decreasing plant-parasitic nematodes or vice versa. However, the mechanism by which WCCs change nematode community assemblages still remains a key question in soil food web ecology. We tested the hypothesis that the long-term use of rye (Secale cereale), barley (Hordeum vulgare) and oat (Avena sativa) as monocultures or mixtures promotes nematode communities and improves overall soil health conditions compared to winter fallow. The results from this study revealed that the use of WCCs generally promoted a higher abundance and diversity of nematode communities, whereas plant parasitic nematodes were the most abundant in winter fallow. Moreover, the mixtures of WCCs had more similar nematode communities compared to rye alone and winter fallow. The structure and enrichment indices were higher with WCCs, indicating higher nutrient cycling and soil suppressiveness, which are signs of healthy soil conditions. Furthermore, WCCs significantly reduced the populations of root lesion nematode Pratylenchus, although their numbers recovered and increased during the main crop stages. Additionally, mixtures of WCCs promoted the highest abundance of the stunt nematode Tylenchorhynchus, whereas winter fallow had a higher abundance of the spiral nematode Helicotylenchus during the fallow period and the main crop stages. The results show that the long-term use of cover crops can have a positive impact on nematode communities and the soil food web, but these changes depend on the type of WCCs and how they are used. [ABSTRACT FROM AUTHOR]

The results of our preliminary studies indicated that the diets of predatory fishes can be bioindicators of faunistic changes in ecosystems and indirectly of changes taking place in aquatic environments in the Pomeranian Bay. We examined the diet composition of top predators Gadus morhua, Sander lucioperca, Perca fluviatilis, and the mesopredator Neogobius melanostomus. The diet composition of the perch, pikeperch, and round goby in the Pomeranian Bay was analyzed for the first time. Our findings indicated that perch, an euryphagous species, is the best potential bioindicator because it is present in the area studied most of the year and has a low to moderate feeding index (FI). Baltic cod, also an euryphagous species, could be a good bioindicator in the areas where it is abundant and occurs frequently, but not in the Pomeranian Bay, where it is caught mainly in the fall. Round goby, which is present in the area studied and had a low FI, is a stenophagous species that preys mainly on benthic species, while pikeperch had a very high FI and the least number of prey species in its diet. The results of trophic interaction analysis among the predators analyzed and their non-native/invasive prey are also provided. [ABSTRACT FROM AUTHOR]

Dietary decisions by predators can affect prey abundance and overall food web dynamics. Many predators do not forage on the same prey at the same frequency throughout their lives. Ontogenetic shifts in prey preference are not, however, often accounted for when modeling food web relationships, despite growing literature that suggests that stage specific dietary relationships may be an important consideration when modeling trophic interactions. We investigated the importance of considering size-structure of a predator population with ontogenetic diet shifts in evaluating relationships with prey response using a manipulative experiment with the brown treesnake (Boiga irregularis) in Guam. After removing ~ 40% of the snake population via toxic mammal carrion, we measured the strength of the relationship between snake density and the response of two types of prey (lizards and mammals). We evaluated these relationships based on total population size or division of the population into stage specific size categories based on diet preference predictions. We hypothesized that the density of juvenile snakes would correlate more strongly with lizard detections, while adult snakes would better correlate to rodent detections. We also measured reproductive output following changes in rates of prey detection. As expected by known ontogenetic shifts in dietary preference, explicit stage-based models better predicted shifts in rates of observed prey items than did total predator density for both lizards and mammals. Additionally, rodent detections were predictive of one reproductive pulse from snakes, while lizard detections were not predictive or correlated. Our findings support that consideration of predatory species stage-based dietary preference can be meaningful for understanding food web dynamics, particularly when a predator has a broad diet or one that changes through time. [ABSTRACT FROM AUTHOR]

Controlled sediment flushing operations (CSFOs) allow to recover reservoirs storage loss while rebalancing the sediment flux interrupted by dams but, at the same time, may cause unacceptable ecological impact. In this study, we investigated the responses of the food web of an upland stream to a CSFO, focusing on the effects of fine sediment deposition detected in three different mesohabitats, i.e., a pool, a riffle, and a step-pool. The field campaign lasted two years and included repeated measurements of fine sediment deposits, and sampling of periphyton, benthic macroinvertebrates and fishes. A moderate and patchy deposition occurred due to the CSFO with short and medium-term ecological impact on the lower trophic levels of the food web, which may affect the whole ecosystem functioning. The monitoring of all available mesohabitats in the investigated stream allowed to detect variations in the ecological response to CSFO, providing a more adequate assessment of the impact. As expected, sedimentation was larger in the pool but, in contrast to our hypotheses, the impact was lower and the recovery was longer for the benthic organisms inhabiting the riffle. In the case of fishes, no lethal impact of both brown trout and bullhead was recorded in the short term but the occurrence of longer lasting effects could not be excluded. To date, this is one of the few studies dealing with a detailed integrative assessment of the downstream impact of sediment management from reservoir on both abiotic and biotic components of stream ecosystem. [ABSTRACT FROM AUTHOR]

This theme issue features 18 papers exploring ecological interactions, encompassing metabolic, social, and spatial connections alongside traditional trophic networks. This integration enriches food web research, offering insights into ecological dynamics. By examining links across organisms, populations, and ecosystems, a hierarchical approach emerges, connecting horizontal effects within organizational levels vertically across biological organization levels. The inclusion of interactions involving humans is a key focus, highlighting the need for their integration into ecology given the complex interactions between human activities and ecological systems in the Anthropocene. The comprehensive exploration in this theme issue sheds light on the interconnectedness of ecological systems and the importance of considering diverse interactions in understanding ecosystem dynamics. This article is part of the theme issue 'Connected interactions: enriching food web research by spatial and social interactions'. [ABSTRACT FROM AUTHOR]

Globally, all marine ecosystems are under pressure by anthropogenic stressors. However, semi-enclosed seas are at a greater risk of degradation due to their limited connectivity to open seas. This leads to a greater accumulation of pollutants and abrupt regime shifts triggered by unsustainable exploitation of living resources, as ecosystems exhibit low degrees of redundancy and more frequent large-scale episodic events such as harmful algal blooms. The Sea of Marmara is a semi-enclosed marine region that has been subjected to various anthropogenic stressors since the 1990s. Recently, local and governmental authorities have employed basin-wide ecosystem management plans to control and manage point and nonpoint (diffuse) sources of pollutants. However, the management of fisheries in relation to the dynamics of the Sea of Marmara food web has attracted less attention from policymakers, even though fisheries exploitation is one of the most significant anthropogenic pressures. In this study, we capitalized on a previous static ecosystem model of the Sea of Marmara by revising and extending it to simulate the changes between 1990 and 2020. We delineated the temporal dynamics and regime shifts in the food web in terms of ecosystem structure and function by using ecological indicators and developed quantitative management advice for its fisheries. The results showed that the ecosystem has experienced three regimes since 1990, with regime shifts occurring with the onset of the 2000s and the mid 2010s. The first regime exhibited high diversity and material cycling, the second regime was characterized by low diversity and increased impact of fisheries, and the third regime culminated in a fished-down food web state. The analysis of fishery dynamics showed that the majority of harvested species were overexploited. We suggest that the implementation of quotas for exploited species should be considered an immediate solution to the unsustainable exploitation of fish stocks and can help restore ecosystem conditions. [ABSTRACT FROM AUTHOR]

The relationship between phytophagous insects and plants is a central aspect of food webs and ecosystem functioning. The introduction of new species into an environment can have significant impacts on the food web of a native ecosystem. In many cases, there is a lack of knowledge on the biology and feeding behavior of invasive species prior their introduction and in the invaded regions. Gut content analyses of insects have provided valuable information on the host spectrum of insects. However, current approaches are time‐consuming and costly. Here, we describe a new molecular gut content analysis (GCA) approach using the Oxford Nanopore (ONT) Flongle sequencing platform to characterize the plant DNA present in the gut of the highly polyphagous insect species Halyomorpha halys. We demonstrate that this technique efficiently amplifies and correctly identifies plant DNA in a mock community. We performed a feeding experiment to determine the sensitivity of this approach and to assess how long the plant DNA can be detected. All plants used in the feeding experiment were correctly identified and detected after 56 days. Surprisingly, we also detected various plant genera that were not included in the feeding experiment and thus were likely ingested months before the experiment. Our study suggests that the GCA using the ONT Flongle sequencing platform represents a rapid and cost‐efficient diagnosis of the dietary preferences, host range, and the diversity of consumed plant species of pest insects with high precision. [ABSTRACT FROM AUTHOR]

Abstract Pulsed flows following heavy monsoon rain events alter riverine food webs, but their impact on headwater stream food webs across the continuum from forested canopy to open agricultural land use remains unclear. We investigated carbon and nitrogen stable isotopes in macroinvertebrates and fish in two tributaries of the Suyeung River, Korea, before and after heavy monsoon rains to assess changes in community trophic niches. Basal resources (leaf litter and biofilms) exhibited consistent δ13C and δ15N values across seasons, with biofilms showing higher δ13C values. δ15N values increased from forested to agricultural reaches, indicating varied nutrient inputs. Consumer isotope values remained stable over time but varied longitudinally, reflecting reliance on local resources. Trophic niches differed between watershed locations but overlapped seasonally. Despite a decrease in consumer δ13C ranges after heavy rainfalls, variations in their δ15N ranges and the ellipse centroid (SEAc) of isotopic niches between sites resulted in broadly consistent SEAc across locations and seasons. This indicates limited evidence for directional reshaping of food-web properties across channel reaches following monsoon rains. Downstream isotopic shifts suggest substantial agricultural influences on food webs. Overall, our findings highlight that monsoon rains may have minimal effects on the community trophic niches of stream food webs.

Abstract The aquaculture industry is growing rapidly and plays a huge role in bridging the global demand gap for fish and other aquatic foods. It is a vital contributor of valuable nutrients and economic benefits. Aquaculture and fisheries provide a means of livelihood to an estimated 58.5 million people globally, according to the United Nations Food and Agriculture Organisation. However, the sector is impacted by the ubiquity of microplastics and toxic chemicals. Although many studies have reported plastic pollution in the aquaculture environment, less attention has been paid to the coexistence of toxic chemicals with plastic particles and the role of climate change in aquaculture food contamination. This review evaluates the occurrence of microplastics in organisms, feeds, water, and sediment in the aquaculture ecosystem and the detection and hazardous effects of toxic chemical contaminants. We also highlight novel insights into the role of climate change in plastic and chemical contamination of aquaculture organisms and ecosystems. We report that the extent of aquaculture’s contribution to global climate change and global plastic pollution is yet to be adequately quantified and requires further investigation for appropriate risk assessment and prevention of food safety crisis. Possible mitigation strategies for the highlighted pollution problems were suggested, and some identified gaps for future research were indicated. Overall, this work is one of the first efforts to assess the influence of climate change on aquaculture food contamination, emphasising its effects on food safety and ecosystem health. Graphical Abstract

Abstract Dietary decisions by predators can affect prey abundance and overall food web dynamics. Many predators do not forage on the same prey at the same frequency throughout their lives. Ontogenetic shifts in prey preference are not, however, often accounted for when modeling food web relationships, despite growing literature that suggests that stage specific dietary relationships may be an important consideration when modeling trophic interactions. We investigated the importance of considering size-structure of a predator population with ontogenetic diet shifts in evaluating relationships with prey response using a manipulative experiment with the brown treesnake (Boiga irregularis) in Guam. After removing ~ 40% of the snake population via toxic mammal carrion, we measured the strength of the relationship between snake density and the response of two types of prey (lizards and mammals). We evaluated these relationships based on total population size or division of the population into stage specific size categories based on diet preference predictions. We hypothesized that the density of juvenile snakes would correlate more strongly with lizard detections, while adult snakes would better correlate to rodent detections. We also measured reproductive output following changes in rates of prey detection. As expected by known ontogenetic shifts in dietary preference, explicit stage-based models better predicted shifts in rates of observed prey items than did total predator density for both lizards and mammals. Additionally, rodent detections were predictive of one reproductive pulse from snakes, while lizard detections were not predictive or correlated. Our findings support that consideration of predatory species stage-based dietary preference can be meaningful for understanding food web dynamics, particularly when a predator has a broad diet or one that changes through time.

Abstract Controlled sediment flushing operations (CSFOs) allow to recover reservoirs storage loss while rebalancing the sediment flux interrupted by dams but, at the same time, may cause unacceptable ecological impact. In this study, we investigated the responses of the food web of an upland stream to a CSFO, focusing on the effects of fine sediment deposition detected in three different mesohabitats, i.e., a pool, a riffle, and a step-pool. The field campaign lasted two years and included repeated measurements of fine sediment deposits, and sampling of periphyton, benthic macroinvertebrates and fishes. A moderate and patchy deposition occurred due to the CSFO with short and medium-term ecological impact on the lower trophic levels of the food web, which may affect the whole ecosystem functioning. The monitoring of all available mesohabitats in the investigated stream allowed to detect variations in the ecological response to CSFO, providing a more adequate assessment of the impact. As expected, sedimentation was larger in the pool but, in contrast to our hypotheses, the impact was lower and the recovery was longer for the benthic organisms inhabiting the riffle. In the case of fishes, no lethal impact of both brown trout and bullhead was recorded in the short term but the occurrence of longer lasting effects could not be excluded. To date, this is one of the few studies dealing with a detailed integrative assessment of the downstream impact of sediment management from reservoir on both abiotic and biotic components of stream ecosystem.

The North Water Polynya is one of the most productive Arctic regions on Earth, sustaining the world's northernmost Inuit communities for millennia. The polynya is a large and persistent region of open water surrounded by sea ice and exhibits high primary productivity, is a biodiversity hotspot, and is a key habitat and migration corridor for Arctic species. Many aspects of the ecosystem structure and the role of resident species in the North Water Polynya remain uncertain. To shed light on these, we developed the first representation of the North Water Polynya food web using the Ecopath modelling framework. Modelled trophic flows indicated that pelagic and benthic communities were primarily connected by Age 1+ Arctic cod (Boreogadus saida), walrus (Odobenus rosmarus), and ringed seal (Pusa hispida). Large copepods, Age 1+ Arctic cod, and bivalves were key prey species. Overall productivity in the North Water Polynya was higher compared to Western Baffin Bay and Western Greenland, corroborating expectations of relatively high productivity within the polynya. This model provides a baseline description of the North Water Polynya ecosystem structure and function prior to future climate-driven food web changes and the emergence of large-scale commercial fisheries.

The understanding of the role of fishes in the trophic functioning of estuaries has increased in stages over many decades. It began with qualitative and quantitative dietary studies, mainly from the 1970s onwards, and progressed to more sophisticated stable isotope work towards the end of the 20th Century and into the present. Building on an initial wide array of predominantly single species rather than community dietary studies, our global knowledge of the food and feeding ecology of fishes in estuaries has now progressed to a stage where we can begin to discern patterns and make generalised statements on the nature and role of fish assemblages in the trophic functioning of these systems. In this review we summarize the dominant aspects relating to the trophic ecology of fishes in estuaries, including ontogenetic changes in fish diet and food provision for the nursery function of estuaries, detritus as a direct and indirect driver of the food web, the influence of latitude and habitat type on trophic structuring, predator prey relationships with an emphasis on the importance of invertebrates in fish food chains, the role of stable isotopes in combination with dietary analyses in understanding trophic functioning, and the effects of environmental change and fishing and other human activities on fish food webs in estuaries. Apart from providing an overview of information on the current status of our knowledge on fish trophic ecology in estuaries, this review also identifies important research gaps that need to be filled. [ABSTRACT FROM AUTHOR]

Abstract Cichlid fishes in the African Great Lakes have undergone explosive speciation, acquiring markedly varying ecologies and diets. There are multiple lineages of scale-eating cichlids, and their natural history and evolutionary ecology is only partially understood. We examined the feeding habit of Docimodus evelynae, a known scale eater, in Lake Malawi. The stomach contents of young individuals mainly consisted of unknown 1 mm hard, white warts (> 30%). To clarify the origin of these warts, we conducted an X-ray fluorometer analysis, and found they were rich in sulphur but low in silicon and calcium, suggesting they were epidermal tissues. Histological and morphological analyses revealed they were multicellular and cup-shaped. These characteristics matched only those of the pearl organs of the coexisting cyprinid Labeo cylindricus. DNA was extracted from the warts found in the stomach of five D. evelynae individuals, followed by PCR using primers targeting the partial COI gene of L. cylindricus. The resulting sequences exhibited 98% similarity to those of L. cylindricus. Pearl organs, never reported as a primary food for fish, could offer a substantial nutritional source based on calorific calculations. Understanding how this peculiar diet is foraged is essential for full comprehension of the food-web structure in this lake.

Abstract The European rabbit has invaded numerous ecosystems worldwide, but rarely steppes. Since its various introduction attempts into the ecosystems of the Magallanes/Fuegian region, the rabbit has become a key player, interacting with species at different trophic levels and generating impacts on ecosystems. To better understand the role of the rabbit in steppe and scrub ecosystems, we characterised the food web in the Magallanes/Fuegian region to understand the identity of their interacting species, the mechanisms and complexities of their interactions to demonstrate that rabbit management may become more complex than just controlling a single species. Based on a bibliographic review and wildlife specialists’ opinions, we built the Magellanic/Fuegian food web, evaluated their topological properties and performed a rabbit extinction simulation to assess the possible short-term ecological mechanisms operating in the community. We found that the network had 206 nodes (64% native, 13% exotic, and 22% mixed) and 535 links among nodes. The European rabbit was the most connected node of the food web, had the second largest dietary breadth, and ranked as the seventh prey item with more predators. A rabbit extinction simulation shows a possible release of herbivory pressure on plants, including that on several native plants (e.g., Gunnera tinctoria, Pratia repens, Gavilea lutea, Tetroncium magellanicus), and a possible release of competition for some herbivores that share resources with the rabbit (e.g., Ovis aries, Lama guanicoe, Bos taurus). Although rabbit predators have a broad and generalist diet, some such as the native Galicitis cuja, could face a 20% reduction in their trophic width and could intensify predation on alternative prey. These results show that the European rabbit is strongly embedded in the Magellanic/Fuegian ecosystem and linked to several native species. Therefore, rabbit management should consider ecosystem approaches accompanied by monitoring programs on native fauna and experimental pilot studies on native flora to conserve the Chilean Patagonia community.

Abstract Background Assessing the historical dynamics of key food web components is crucial to understand how climate change impacts the structure of Arctic marine ecosystems. Most retrospective stable isotopic studies to date assessed potential ecosystem shifts in the Arctic using vertebrate top predators and filter-feeding invertebrates as proxies. However, due to long life histories and specific ecologies, ecosystem shifts are not always detectable when using these taxa. Moreover, there are currently no retrospective stable isotopic studies on various other ecological and taxonomic groups of Arctic biota. To test whether climate-driven shifts in marine ecosystems are reflected in the ecology of short-living mesopredators, ontogenetic changes in stable isotope signatures in chitinous hard body structures were analysed in two abundant squids (Gonatus fabricii and Todarodes sagittatus) from the low latitude Arctic and adjacent waters, collected between 1844 and 2023. Results We detected a temporal increase in diet and habitat-use generalism (= opportunistic choice rather than specialization), trophic position and niche width in G. fabricii from the low latitude Arctic waters. These shifts in trophic ecology matched with the Atlantification of the Arctic ecosystems, which includes increased generalization of food webs and higher primary production, and the influx of boreal species from the North Atlantic as a result of climate change. The Atlantification is especially marked since the late 1990s/early 2000s. The temporal patterns we found in G. fabricii’s trophic ecology were largely unreported in previous Arctic retrospective isotopic ecology studies. Accordingly, T. sagittatus that occur nowadays in the high latitude North Atlantic have a more generalist diet than in the XIXth century. Conclusions Our results suggest that abundant opportunistic mesopredators with short life cycles (such as squids) are good candidates for retrospective ecology studies in the marine ecosystems, and to identify ecosystem shifts driven by climate change. Enhanced generalization of Arctic food webs is reflected in increased diet generalism and niche width in squids, while increased abundance of boreal piscivorous fishes is reflected in squids’ increased trophic position. These findings support opportunism and adaptability in squids, which renders them as potential winners of short-term shifts in Arctic ecosystems.

The European rabbit has invaded numerous ecosystems worldwide, but rarely steppes. Since its various introduction attempts into the ecosystems of the Magallanes/Fuegian region, the rabbit has become a key player, interacting with species at different trophic levels and generating impacts on ecosystems. To better understand the role of the rabbit in steppe and scrub ecosystems, we characterised the food web in the Magallanes/Fuegian region to understand the identity of their interacting species, the mechanisms and complexities of their interactions to demonstrate that rabbit management may become more complex than just controlling a single species. Based on a bibliographic review and wildlife specialists' opinions, we built the Magellanic/Fuegian food web, evaluated their topological properties and performed a rabbit extinction simulation to assess the possible short-term ecological mechanisms operating in the community. We found that the network had 206 nodes (64% native, 13% exotic, and 22% mixed) and 535 links among nodes. The European rabbit was the most connected node of the food web, had the second largest dietary breadth, and ranked as the seventh prey item with more predators. A rabbit extinction simulation shows a possible release of herbivory pressure on plants, including that on several native plants (e.g., Gunnera tinctoria, Pratia repens, Gavilea lutea, Tetroncium magellanicus), and a possible release of competition for some herbivores that share resources with the rabbit (e.g., Ovis aries, Lama guanicoe, Bos taurus). Although rabbit predators have a broad and generalist diet, some such as the native Galicitis cuja, could face a 20% reduction in their trophic width and could intensify predation on alternative prey. These results show that the European rabbit is strongly embedded in the Magellanic/Fuegian ecosystem and linked to several native species. Therefore, rabbit management should consider ecosystem approaches accompanied by monitoring programs on native fauna and experimental pilot studies on native flora to conserve the Chilean Patagonia community. [ABSTRACT FROM AUTHOR]

Rivers are constantly disturbed by anthropogenic stressors. Developing robust biotic indicators to assess river environments across large spatial scales is important. In the subtropical Liuxi River of China, 34 native fish indicators, including 4 genera and 30 species, were selected from 108 fish species by linear discriminant analysis. These indicators were grouped into 19 ecological items and assigned evaluation scores according to the roles they played in the food web (e.g., keystoneness and trophic level) and their positive feedback on the environment (e.g., requirements for feeding, spawning/nursing, and migrating). Three formulae for calculating the index of fish indicators (IFI) were developed based on the scoring of each indicator and weighted by relative abundance (individual number, i.e., IFI[INF]N[/INF]) and relative biomass (wet weight, i.e., IFI[INF]B[/INF]). Spearman correlation analysis showed that IFI[INF]B[/INF], which had positive (P< 0.05) correlations with elevation (m), dissolved oxygen (mg/L), flow velocity (cm/s), Shannon-Wiener diversity, benthic index of biotic integrity, exhibited a more powerful explanation of biodiversity and environmental factors than IFI[INF]N[/INF] and unweighted IFI. Therefore, IFI[INF]B[/INF] was most suitable for constructing a scoring system to evaluate ecological status (e.g., water and habitat quality). These results suggested that fish indicator-based scoring and evaluation system was effectively in not only assessing the siteor region-specific ecological status bot also reflecting the fluvial biodiversity and food web integrity. Further application and promotion of this indicator-based evaluation method may improve field investigation efficiency and contribute greatly to the conservation and management of river ecosystems. [ABSTRACT FROM AUTHOR]

Dispersal is a well-recognized driver of ecological and evolutionary dynamics, and simultaneously an evolving trait. Dispersal evolution has traditionally been studied in single-species metapopulations so that it remains unclear how dispersal evolves in metacommunities and metafoodwebs, which are characterized by a multitude of species interactions. Since most natural systems are both species-rich and spatially structured, this knowledge gap should be bridged. Here, we discuss whether knowledge from dispersal evolutionary ecology established in single-species systems holds in metacommunities and metafoodwebs and we highlight generally valid and fundamental principles. Most biotic interactions form the backdrop to the ecological theatre for the evolutionary dispersal play because interactions mediate patterns of fitness expectations across space and time. While this allows for a simple transposition of certain known principles to a multispecies context, other drivers may require more complex transpositions, or might not be transferred. We discuss an important quantitative modulator of dispersal evolution—increased trait dimensionality of biodiverse meta-systems—and an additional driver: co-dispersal. We speculate that scale and selection pressure mismatches owing to co-dispersal, together with increased trait dimensionality, may lead to a slower and more 'diffuse' evolution in biodiverse meta-systems. Open questions and potential consequences in both ecological and evolutionary terms call for more investigation. This article is part of the theme issue 'Diversity-dependence of dispersal: interspecific interactions determine spatial dynamics'. [ABSTRACT FROM AUTHOR]

As global heating and other anthropogenic influences alter tropical marine environments, it is unclear how marine bird populations will be impacted and whether their current roles in tropical marine ecosystems will change. Although marine birds roost and breed on tropical islands in large numbers, the direct trophic interactions between these birds and their prey across the tropics are poorly documented. We present a first framework for evaluating the dependence on and contributions of marine birds to tropical coral reef ecosystems and use it to examine the evidence for different kinds of interaction, focusing primarily on avian diets. We found 34 publications between 1967 and 2023 that presented a total of 111 data sets with enough detail for quantitative dietary analysis of tropical marine birds. Only two bird species out of 37 (5.4%) had diets of >50% coral reef fishes and only one, the Pacific Reef Egret, appeared to depend almost entirely on reef‐based production. Marine birds are also prey for other marine organisms, but insufficient data are available for quantitative analysis. Evidence for indirect effects of birds in tropical marine environments is stronger than for direct dependence on coral reefs, particularly in relation to nutrient concentration and the fertilisation impacts of guano on corals. Dispersal of propagules (e.g. seeds, spores, invertebrate eggs) by bathing, drinking, resting or foraging birds is under‐studied and poorly documented. Although the degradation of coral reefs appears unlikely to have a significant direct impact on food availability for most marine bird populations, indirect effects involving marine birds may be disrupted by global environmental change. [ABSTRACT FROM AUTHOR]

Animals occupying higher trophic levels can have disproportionately large influence on ecosystem structure and functioning, owning to intricate behavioral responses to their environment, but the effects of behavioral adaptations on aquatic ecosystem dynamics are underrepresented, especially in model studies. Here, we explore how adaptive behavior of fish can affect the dynamics of aquatics ecosystems. We frame fish behavior in the context of the central trade‐off between feeding and predation, calculating the optimal level of feeding determined by ambient food availability and predation risk. To explore whole‐ecosystem consequences of fish behavior, we embed our behavioral model within the Water Ecosystems Tool (WET), a contemporary end‐to‐end aquatic ecosystem model. The principle of optimality provides a robust and mechanistic framework for representing animal behavior that is relevant for complex models, and can provide a stabilizing effect on model dynamics. The model predicts an emergent functional response similar to Holling type III, but with richer dynamics and a more rigorous theoretical foundation. We show how adaptive fish behavior works to stabilize food web dynamics compared to a control model with no optimal behavior, and how changing the strength of the underlying trade‐off has profound effects on trophic control and food web structure. Furthermore, we demonstrate how including fish behavior allows for an overall more realistic response of the model system to environmental perturbation in the form of nutrient enhancement. We discuss the structuring effects of behavioral adaptations in real ecosystems, and how approaches like this one may benefit aquatic ecological modeling. Our study further highlights how a mechanistic approach based on concepts from theoretical ecology can be successfully implemented in complex operational models resulting in improved dynamics and descriptive power. [ABSTRACT FROM AUTHOR]

Agricultural practices shape arthropod communities in arable fields, consequently influencing their interactions and the resulting ecosystem services, in particular pest regulation. Predatory arthropods play a pivotal role by preying on herbivores, soil fauna, and on other predators. However, the intricate mechanisms through which agricultural practices shape the dietary preferences of predators, and regulate herbivore populations remain complex and inadequately understood.We assessed how fertilisation with organic fertiliser and extending crop rotations with perennial ley affected predation pressure across prey taxa. We mapped predator and prey trophic linkages with molecular analysis of carabid predator gut contents, and measured densities and taxonomic richness of predators, herbivores, and soil fauna in 19 cereal fields during three samplings across the growing season.We derived two food web structure metrics: prey vulnerability that is the average number of predators feeding on a selected prey, and predator trophic redundancy, that is dietary overlap. Prey vulnerability was compared among soil fauna, herbivores, and other predator species (that is interspecific intraguild predation) over the growing season, and across treatments. The mechanistic underpinnings of observed shifts in vulnerability of herbivorous prey at different crop stages were identified using information criteria to select among candidate variables related to the richness, density and interaction structure of the different guilds during both the current, and the previous crop stages.Agricultural diversification via organic fertilisation combined with perennial ley in the crop rotation decreased the vulnerability of both intraguild prey and soil fauna prey, and stabilised herbivore vulnerability. Mechanistically, the vulnerability of herbivorous prey at crop ripening emerges from the combination of predator richness and trophic redundancy during this sampling round, rather than from carryover effects from previous crop stages.Synthesis and applications: Our results suggest that locally provided resource continuity through diversified cropping practices bolster biological pest regulation, thus underline the importance of lesser disturbance in arable ecosystems for the provision of ecosystem services. Enhanced predator species richness together with availability of alternative prey through the season underpins this enhanced pest regulation. [ABSTRACT FROM AUTHOR]

Simple Summary: Carabids are abundant and diverse arthropods in agroecosystems and are well known for their generalist diet and therefore biocontrol potential. Most studies on carabids' diet have focused on periods of peak pest infestations but their feeding habits through the cropping season are poorly known. In this study, we explored how carabids' trophic interactions with pests (aphids and slugs) and alternative prey (spiders, earthworms and springtails) varied from the wheat seedling emergence to wheat ripening by analysing the prey DNA in their gut. Carabids seemed to switch between prey depending on their availability at the time, reaffirming carabids' opportunistic diet. Regarding biocontrol, carabid taxa contributed complementarily to pest predation over the season and per pest taxon, highlighting the importance of favouring diversity in agroecosystems. To date, evaluating the diets of natural enemies like carabids has largely been limited to spatially explicit and short-term sampling. This leaves a knowledge gap for the intra-annual dynamics of carabid diets, and the provision and timing of delivery of natural pest control services. Season-long pitfall trapping of adult carabids was conducted in conventional winter wheat fields, from November 2018 to June 2019, in five French departments. Diagnostic Multiplex PCR of carabid gut contents was used to determine the dynamics of carabid diets. The overall detection rate of target prey DNA was high across carabid individuals (80%) but varied with the prey group. The rate of detection was low for pests, at 8.1% for slugs and 9.6% for aphids. Detection of intraguild predation and predation on decomposers was higher, at 23.8% for spiders, 37.9% for earthworms and 64.6% for springtails. Prey switching was high at the carabid community level, with pest consumption and intraguild predation increasing through the cropping season as the availability of these prey increased in the environment, while the detection of decomposer DNA decreased. Variation in diet through the cropping season was characterized by: (i) complementary predation on slug and aphid pests; and (ii) temporal complementarity in the predominant carabid taxa feeding on each pest. We hypothesize that natural pest control services delivered by carabids are determined by complementary contributions to predation by the different carabid taxa over the season. [ABSTRACT FROM AUTHOR]

Stable isotope analysis has been broadly used to study food webs, but often relies on inaccurate assumptions of trophic isotopic discriminations, which could lead to misinterpretation of obtained results. While many taxa exhibit similar trophic discrimination factors (TDFs), crayfish, exhibit omnivorous feeding strategies, yet TDFs are missing. In this study, we determined TDFs and tissue biokinetic parameters of the marbled crayfish Procambarus virginalis as a model species. Moreover, we compared commonly used TDFs and those determined from this study and applied them across species and ecosystems as a first attempt to compare the effect of species-specific TDFs in Bayesian trophic mixing models. Our results revealed differences between the TDFs of different tissues and biokinetic parameters of crayfish. Our result also revealed TDFs differences between crayfish relying mostly on plants versus those relying on an animal diet. We found differences of TDF suitability among species and ecosystems, highlighting the need for specific TDFs for different crayfish species. This study improves our understanding and the need for species-calibrated TDFs for robust statistical analysis of stable isotope data. Our approach is widely applicable across taxa and ecosystems to reduce the bias introduced by using unspecific TDFs in Bayesian mixing models. [ABSTRACT FROM AUTHOR]

Climate change has led to significant fluctuations in marine ecosystems, including alterations in the structure and function of food webs and ecosystem status. Coastal ecosystems are critical to the functioning of the earth's life-supporting systems. However, temporal variations in most of these ecosystems have remained unclear so far. In this study, we employed a linear inverse model with Markov Chain Monte Carlo (LIM-MCMC) combined with ecological network analysis to reveal the temporal variations of the food web in Haizhou Bay of China. Food webs were constructed based on diet composition data in this ecosystem during the year of 2011 and 2018. Results indicated that there were obvious temporal variations in the composition of food webs in autumn of 2011 and 2018. The number of prey and predators for most species in food web decreased in 2018 compared with 2011, especially for Trichiurus lepturus, zooplankton, Amblychaeturichthys hexanema, and Loligo sp. Ecological network analysis showed that the complexity of food web structure could be reflected by comprehensive analysis of compartmentalized indicators. Haizhou Bay ecosystem was more mature and stable in 2011, while the ecosystem's self-sustainability and recovery from disturbances were accelerated from 2011 to 2018. These findings contribute to our understanding of the dynamics of marine ecosystems and highlight the importance of comprehensive analysis of marine food webs. This work provides a framework for assessing and comparing temporal variations in marine ecosystems, which provides essential information and scientific guidance for the Ecosystem-based Fisheries Management. [ABSTRACT FROM AUTHOR]

One of the least understood trophic pathways on coral reefs is the linkage between highly productive cryptic motile invertebrates (herein: cryptofauna) and the predatory vertebrates that underpin reef fisheries. As cryptofauna are difficult to observe and quantify, particularly in coral rubble where they proliferate, the diets of invertivores that forage in rubble have largely been determined through relative gut content analyses. Without congruent quantification of prey diversity, biomass, and rates of predation specific to rubble, it remains challenging to develop models of productivity and energy transfer. We calculated bite rates of six wrasses (Labridae) and a goatfish (Mullidae) commonly found foraging in rubble, using in situ videography on a coral reef in Palau, Western Micronesia. Consumption rates (i.e. individuals consumed) and prey preferences were determined using tank-based feeding experiments, where individual fish were presented with a diverse rubble community characterised before and after 2 h feeding trials. The motile cryptofauna community and invertivore diet consisted predominantly of Arthropoda (83% and > 58%, respectively), with calanoid copepods and mysids positively selected and harpacticoids, decapods and ostracods negatively selected. The interspecific mean (± standard error) rate of consumption was 3.5 ± 0.2 ind. min−1 from rubble, estimated to equal 9.5 ± 0.9 mg min−1 of invertebrate biomass consumed per fish, with biased uptake of small fauna. Bite and consumption rates varied among species with the greatest efficiency in biomass uptake evident in Halichoeres melanurus. This study provides a first attempt at characterising diverse cryptofauna communities pre- and post-trial to identify feeding rates and preferences of coral reef invertivores from the rubble benthos, and highlights the importance of addressing the bioavailability of lower trophic entities in energy pathways. [ABSTRACT FROM AUTHOR]

A systematic study of the interaction of hydrobiological, hydrochemical, hydrological, and hydrophysical processes that occur in the ecosystem of the Vistula Lagoon (VL) of the Baltic Sea has been carried out using mathematical modeling and taking into account the processes in the active layer of bottom sediments (BSs). The features of the dynamics of nitrogen and phosphorus compounds, the turnover time, and the components of the balance of compounds of biogenic elements in the VL ecosystem, as well as the degree of their temporal variability, have been analyzed. It is shown that the variability of nitrogen and phosphorus compounds in the aquatic environment increases in spring and autumn periods. This is due to an increase in river flow into the lagoon and an increase in the level of external biogenic load on the water area of the VL. Model calculations of matter fluxes allow us to state that the inputs of dissolved organic and suspended matter into the lagoon from external sources and the removal to the Baltic Sea are important processes that significantly affect their content in the VL ecosystem. It has been established that under strong winds the process of sedimentation of suspensions can be largely blocked, and the intensity of BS resuspension can increase significantly. An analysis of the main qualitative and quantitative features of the nature of the temporal dynamics of the DON and DOP turnover times, as well as the mineral compounds of nitrogen and phosphorus, indicates a close conjugation of the processes of transformation of dissolved organic and inorganic substances in the water of the VL. A quantitative assessment of the processes of consumption and excretion of compounds of biogenic elements by different groups of aquatic organisms has been performed, and the important role of heterotrophic bacterioplankton and protozoa in the processes of transformation of compounds of nutrients in the VL ecosystem has been shown. The model can be used for scenario modeling and analyzing possible changes in the VL ecosystem under changing climatic and anthropogenic conditions. [ABSTRACT FROM AUTHOR]

The date palm (Phoenix dactylifera L.) (Arecales: Arecaceae) is the most economically important crop in Oman with an annual production of >360,000 tons of fruit. The Dubas bug (Ommatissus lybicus de Bergevin) (Hemiptera: Tropiduchidae) is one of the major pests of date palms, causing up to a 50% reduction in fruit production. Across the course of 2 seasons, a variety of arthropod predators living in the date palm canopy were investigated for possible biological control of Dubas bugs, given the growing interest in nonchemical insect pest control in integrated pest management. We collected ~6,900 arthropod predators directly from date palm fronds from 60 Omani date palm plantations and tested them for Dubas bug predation using PCR-based molecular gut content analysis. We determined that ≥56 species of arthropod predators feed on the Dubas bug. We found that predatory mites, ants, and the entire predator community combined showed a positive correlation between predation detection frequency and increasing Dubas bug density. Additionally, there was a significant impact of season on gut content positives, with the spring season having a significantly higher percentage of predators testing positive for Dubas bug, suggesting this season could be the most successful time to target conservation biological control programs utilizing a diverse suite of predators. [ABSTRACT FROM AUTHOR]

Chondrichthyans form an important part of marine food webs as top predators and mesopredators. However, little is known about chondrichthyans in Namibian waters and the roles they play in ecosystem function. During efforts to disentangle Cape fur seals Arctocephalus pusillus pusillus from fishing gear or plastic debris, 11 incidents of seals impaled by the dorsal spines of St Josephs Callorhinchus capensis (order Chimaeriformes) were recorded. These observations overlapped with mass die-offs of the seals owing to food shortages, as indicated by large numbers of emaciated seals and widespread miscarriages of seal foetuses. This suggests that the St Joseph is not a desirable prey species for Cape fur seals, though this chimaera may provide a source of food, especially when preferred prey species are unavailable. This is the first published record of Cape fur seals feeding on chondrichthyans in Namibian waters. Documenting these types of food-web linkages between pinnipeds and chondrichthyans will allow for a better understanding of how impacts on their populations may more broadly affect Namibia's marine ecosystems. [ABSTRACT FROM AUTHOR]

Particulate organic matter (POM) is an important energy source for aquatic consumers, understanding its origin and composition is essential for understanding the energetic dynamics of aquatic environments. The aim of this study was to analyze the relationship between POM and phytoplankton (isotopic values and chlorophyll concentration) and abiotic variables during dry and rainy seasons. Sampling was conducted in rivers and lagoons in the floodplain of the Upper Paraná River. We found a greater difference in δ13C values of POM between sampling points than between seasons, indicating that the composition of regional sources influences the composition of POM more than dry and rainy seasons. In addition, the concentration of chlorophyll during the dry season was positively correlated with δ13C values during that rainy period. Additionally, we found a relationship between factors limiting the growth of phytoplankton and δ13C values of POM, such as phosphate ions, indicating that variables that regulate phytoplankton growth tend to influence the composition of POM in river floodplains. Therefore, maintaining the variables that regulate the phytoplankton community is of fundamental importance for the composition of POM, an important energy source in aquatic environments. [ABSTRACT FROM AUTHOR]

Motivation: The metaweb is a dictionary of nodes and their potential interactions developed for a particular region, focusing on a particular type of ecosystem. Based on the local biodiversity information at different spatial and temporal scales, the regional metaweb can be easily decomposed into local webs. The generated local webs are useful for understanding spatiotemporal variations in ecological interactions in a particular region. In this study, an attempt was made to develop a trophic metaweb for freshwater ecosystems in South Korea, called the KF‐metaweb. The metaweb contains 23,074 interactions between 446 taxa collected from 730 studies. This metaweb can be used to understand the spatiotemporal variability of different local food webs and the effects of the environment on food web properties. Furthermore, this is the first metaweb developed for any Asian ecosystem that contains information about many interactions that are unavailable in any other existing database. In addition, this metaweb study enriches our global understanding of ecological interactions. Main Types of Variables Contained: The data contained trophic interactions between resources (prey) and consumers (predators). Spatial Location and Grain: The mainland of South Korea and Jeju Island. Time Period and Grain: 2008–2021. Major Taxa: Microalgae (belonging to the phyla Cyanobacteria, Bygra, Cryophyta, Myozoa, Ochrophyta, Charophyta, Chlorophyta, Euglenozoa and Mycetozoa), zooplankton (belonging to the phyla Arthropoda and Rotifera), benthic macroinvertebrates (Platyhelmenthes, Annelida, Arthropoda and Mollusca) and fish. Level of Measurement: Minimum taxonomic resolution was at the genus level for fish and benthic macroinvertebrates and order level for zooplankton and microalgae. Software Format: Excel (*.xlsx). [ABSTRACT FROM AUTHOR]

This study was undertaken to elucidate the food web structure and interspecific interactions in the lakes and reservoirs undergoing eutrophication and to assess the efficacy of lake-wide non-traditional biomanipulation (direct predation of cyanobacteria by proliferating planktivorous fish) for bloom management. Analyses of aquatic organisms and stable isotopes of basic food sources and consumers were performed for Zhangze Reservoir in North-central China. Additionally, an improved scheme based on plankton changes and interspecific interactions is proposed on this basis. Compared with other widely-studied eutrophic reservoirs, the δ15N value of each component of the food web in Zhangze Reservoir was higher, the food chain was relatively long and the δ13C range of fish consumers was narrower. Planktivorous fish consumed phytoplankton as their primary food source. However, the phytoplankton biomass and the percentage of cyanobacteria increased, and eutrophication did not improve. The findings concerning the composition of consumers and their food sources in Zhangze Reservoir indicate the urgent need to change the fish structure to optimise the structure of plankton community and mitigate phytoplankton overgrowth. The study findings provide a basis for the implementation of effective eutrophication management strategies in lakes and reservoirs where planktivorous fish are prevalent. [ABSTRACT FROM AUTHOR]

Direct exploitation through fishing is driving dramatic declines of wildlife populations in ocean environments, particularly for predatory and large‐bodied taxa. Despite wide recognition of this pattern and well‐established consequences of such trophic downgrading on ecosystem function, there have been few empirical studies examining the effects of fishing on whole system trophic architecture. Understanding these kinds of structural impacts is especially important in coral reef ecosystems—often heavily fished and facing multiple stressors. Given the often high dietary flexibility and numerous functional redundancies in diverse ecosystems such as coral reefs, it is important to establish whether web architecture is strongly impacted by fishing pressure or whether it might be resilient, at least to moderate‐intensity pressure. To examine this question, we used a combination of bulk and compound‐specific stable isotope analyses measured across a range of predatory and low‐trophic‐level consumers between two coral reef ecosystems that differed with respect to fishing pressure but otherwise remained largely similar. We found that even in a high‐diversity system with relatively modest fishing pressure, there were strong reductions in the trophic position (TP) of the three highest TP consumers examined in the fished system but no effects on the TP of lower‐level consumers. We saw no evidence that this shortening of the affected food webs was being driven by changes in basal resource consumption, for example, through changes in the spatial location of foraging by consumers. Instead, this likely reflected internal changes in food web architecture, suggesting that even in diverse systems and with relatively modest pressure, human harvest causes significant compressions in food chain length. This observed shortening of these food webs may have many important emergent ecological consequences for the functioning of ecosystems impacted by fishing or hunting. Such important structural shifts may be widespread but unnoticed by traditional surveys. This insight may also be useful for applied ecosystem managers grappling with choices about the relative importance of protection for remote and pristine areas and the value of strict no‐take areas to protect not just the raw constituents of systems affected by fishing and hunting but also the health and functionality of whole systems. [ABSTRACT FROM AUTHOR]

Introduction: Increasing temperature of the global ocean alters the spatial behavior of a number of species. From the northern Atlantic Ocean, species may shift their area towards the poles. This results in the atlantification of the Barents Sea, raising questions about possible changes in species composition, community structure and community control. Methods: We address the question whether possible changes in community control can be detected and quantified based on simple network analytical measures applied to the food web. Based on unweighted (binary) and undirected (symmetric) data, we quantify the strength of direct and indirect interactions in the network, represent the most asymmetric effects in the asymmetry graph composed of directed and weighted links and study the overlap among trophic niches of organisms. Results and discussion: We support earlier findings suggesting that the ecosystem can possibly be characterized by wasp-waist control. This would mean that focusing management efforts on intermediate trophic levels is of high importance, providing indirect benefit for organisms also at lower and higher trophic levels. [ABSTRACT FROM AUTHOR]