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Abstract Ecosystems are interconnected by energy fluxes that provide resources for the inhabiting organisms along the transition zone. Especially where in situ resources are scarce, ecosystems can become highly dependent on external resources. The dependency on external input becomes less pronounced in systems with elevated in situ production, where only consumer species close to the site of external input remain subsidized, whereas species distant to the input site rely on the in situ production of the ecosystem. It is largely unclear though if this pattern is consistent over different consumer species and trophic levels in one ecosystem, and whether consumer species that occur both proximate to and at a distance from the input site differ in their dependency on external resource inputs between sites. Using stable isotope analysis, we investigated the dependency on external marine input for common ground‐associated consumer taxa on small tropical islands with high in situ production. We show that marine input is only relevant for strict beach‐dwelling taxa, while the terrestrial vegetation is the main carbon source for inland‐dwelling taxa. Consumer species that occurred both close (beach) and distant (inland) to the site of marine input showed similar proportions of marine input in their diets. This supports earlier findings that the relevance of external resources becomes limited to species close to the input site in systems with sufficient in situ production. However, it also indicates that the relevance of external input is also species‐dependent, as consumers occurring close and distant to the input site depended equally strong or weak on marine input.

Abstract DNA metabarcoding is an emerging tool used to quantify diet in environments and consumer groups where traditional approaches are unviable, including small‐bodied invertebrate taxa. However, metabarcoding of small taxa often requires DNA extraction from full body parts (without dissection), and it is unclear whether surface contamination from body parts alters presumed diet presence or diversity. We examined four different measures of diet (presence, rarefied read abundance, richness, and species composition) for a terrestrial invertebrate consumer (the spider Heteropoda venatoria) both collected in its natural environment and fed an offered diet item in contained feeding trials using DNA metabarcoding of full body parts (opisthosomas). We compared diet from consumer individuals surface sterilized to remove contaminants in 10% commercial bleach solution followed by deionized water with a set of unsterilized individuals. We found that surface sterilization did not significantly alter any measure of diet for consumers in either a natural environment or feeding trials. The best‐fitting model predicting diet detection in feeding trial consumers included surface sterilization, but this term was not statistically significant (β = −2.3, p‐value = .07). Our results suggest that surface contamination does not seem to be a significant concern in this DNA diet metabarcoding study for consumers in either a natural terrestrial environment or feeding trials. As the field of diet DNA metabarcoding continues to progress into new environmental contexts with various molecular approaches, we suggest ongoing context‐specific consideration of the possibility of surface contamination.

We propose an intraguild predation ecological system consisting of a tri-trophic food web with a fear response for the basal prey and a Lotka–Volterra functional response for predation by both a specialist predator (intraguild prey) and a generalist predator (intraguild predator), which we call the superpredator. We prove the positivity, existence, uniqueness, and boundedness of solutions, determine all equilibrium points, prove global stability, determine local bifurcations, and illustrate our results with numerical simulations. An unexpected outcome of the prey's fear of its specialist predator is the potential eradication of the superpredator.

Ecosystem structure—that is the species present, the functions they represent, and how those functions interact—is an important determinant of community stability. This in turn affects how ecosystems respond to natural and anthropogenic crises, and whether species or the ecological functions that they represent are able to persist. Here we use fossil data from museum collections, literature, and the Paleobiology Database to reconstruct trophic networks of Tethyan paleocommunities from the Anisian and Carnian (Triassic), Bathonian (Jurassic), and Aptian (Cretaceous) stages, and compare these to a previously reconstructed trophic network from a modern Jamaican reef community. We generated model food webs consistent with functional structure and taxon richnesses of communities, and compared distributions of guild level parameters among communities, to assess the effect of the Mesozoic Marine Revolution on ecosystem dynamics. We found that the trophic space of communities expanded from the Anisian to the Aptian, but this pattern was not monotonic. We also found that trophic position for a given guild was subject to variation depending on what other guilds were present in that stage. The Bathonian showed the lowest degree of trophic omnivory by top consumers among all Mesozoic networks, and was dominated by longer food chains. In contrast, the Aptian network displayed a greater degree of short food chains and trophic omnivory that we attribute to the presence of large predatory guilds, such as sharks and bony fish. Interestingly, the modern Jamaican community appeared to have a higher proportion of long chains, as was the case in the Bathonian. Overall, results indicate that trophic structure is highly dependent on the taxa and ecological functions present, primary production experienced by the community, and activity of top consumers. Results from this study point to a need to better understand trophic position when planning restoration activities because a community may be so altered by human activity that restoring a species or its interactions may no longer be possible, and alternatives must be considered to restore an important function. Further work may also focus on elucidating the precise roles of top consumers in moderating network structure and community stability.

Abstract Aeglids are endemic crustaceans from the Neotropical region of South America, with great importance in the freshwater food chain. We investigated the trophic relationships in different streams containing Aegla castro Schmitt, 1942 through the use of stable isotopes, testing the hypothesis that these animals occupy a lower position and that the environments are different and will modulate the isotopic ratios of carbon and nitrogen. Aegla castro showed a low trophic level in all locations, being an important link between producers and other trophic levels. They present differences in their isotopic signature for the sampling areas, indicating that environment can be a factor that modulates the trophic webs. We did not find intraspecific differences in isotopic signatures, probably due to the similar food items consumed by both juveniles and adults foraging in the same locations. Studies like this are becoming increasingly important due to the rapid degradation of freshwater environments and the lack of trophic knowledge about these endemic animals. It is increasingly important to understand how environmental changes (such as through anthropogenic action) is interfering in freshwater trophic relationships, and how this can affect the permanence of aeglids.

Trophic cascades, or indirect effects of predators on non-adjacent lower trophic levels, are a classic phenomenon in ecology, and are thought to be strongest in aquatic ecosystems. Most research on freshwater trophic cascades focused on temperate lakes, where fish are present and where Daphnia frequently dominate the zooplankton community. These studies identified that Daphnia often play a key role in facilitating trophic cascades by linking fish to algae with strong food web interactions. However, Daphnia are rare or absent in most tropical and subtropical lowland freshwaters, and fish are absent from small and temporary water bodies, where invertebrates fill the role of top predator. While invertebrate predators are ubiquitous in freshwater systems, most have received little attention in food web research. Therefore, we aimed to test whether trophic cascades are possible in small warmwater ponds where Daphnia are absent and small invertebrates are the top predators. We collected naturally occurring plankton communities from small fishless water bodies in central Texas and propagated them in replicate pond mesocosms. We removed zooplankton from some mesocosms, left the plankton community intact in others, and added one of two densities of the predaceous insect Neoplea striola to others. Following an incubation period, we then compared biomasses of plankton groups to assess food web effects between the trophic levels, including whether Neoplea caused a trophic cascade by reducing zooplankton. The zooplankton community became dominated by copepods which prefer large phytoplankton and exhibit a fast escape response. Perhaps due to these qualities of the copepods and perhaps due to other reasons such as high turbidity impairing predation, no evidence for food web effects were found other than somewhat weak evidence for zooplankton reducing large phytoplankton. More research is needed to understand the behavior and ecology of Neoplea, but trophic cascades may generally be weak or absent in fishless low latitude lowland water bodies where Daphnia are rare.

Dietary lipids (DLs), particularly sterols and fatty acids, are precursors for endogenous lipids that, unusually for macronutrients, shape cellular and organismal function long after ingestion. These functions – cell membrane structure, intracellular signalling, and hormonal activity – vary with the identity of DLs, and scale up to influence health, survival, and reproductive fitness, thereby affecting evolutionary change. Our Ecological Lipidology approach integrates biochemical mechanisms and molecular cell biology into evolution and nutritional ecology. It exposes our need to understand environmental impacts on lipidomes, the lipid specificity of cell functions, and predicts the evolution of lipid-based diet choices. Broad interdisciplinary implications of Ecological Lipidology include food web alterations, species responses to environmental change, as well as sex differences and lifestyle impacts on human nutrition, and opportunities for DL-based therapies.

Understanding variations in metal levels in biota geographically and under different environmental conditions is essential to determining risk to organisms themselves and to their predators. It is often difficult to determine food chain relationships because predators may eat several different prey types. Horseshoe crab (Limulus polyphemus) eggs form the basis for a complex food web in Delaware Bay, New Jersey, USA. Female horseshoe crabs lay thumb-sized clutches of eggs, several cm below the surface, and often dislodge previously laid eggs that are brought to the surface by wave action, where they are accessible and critical food for migrant shorebirds. This paper compares metal and metalloid (chromium [Cr], cadmium [Cd], lead [Pb], mercury [Hg], arsenic [As] and selenium [Se]) concentrations in horseshoe crab eggs collected on the surface with concentrations in eggs from clutches excavated from below the sand surface, as well as examining metals in eggs from different parts of the Bay. The eggs were all collected in May 2019, corresponding to the presence of the four main species of shorebirds migrating through Delaware Bay. These migrating birds eat almost entirely horseshoe crab eggs during their stopover in Delaware Bay, and there are differences in the levels of metals in blood of different shorebirds. These differences could be due to whether they have access to egg clutches below sand (ruddy turnstones, Arenaria interpres) or only to eggs on the surface (the threatened red knot [Calidris canutus rufa] and other species of shorebirds). Correlations between metals in clutches were also examined. Except for As and Cd, there were no significant differences between the metals in crab egg clutches and eggs on the surface that shorebirds, gulls, and other predators eat. There were significant locational differences in metal levels in horseshoe crab eggs (except for Pb), with most metals being highest in the sites on the lower portion of Delaware Bay. Most metals in crab eggs have declined since studies were conducted in the mid-1990s but were similar to levels in horseshoe crab eggs in 2012. The data continue to provide important monitoring and assessment information for a keystone species in an ecosystem that supports many species, including threatened and declining shorebird species during spring migration.

Water‐filled tree holes are unique ecosystems that may occur high up in tree crowns and are essentially aquatic islands in the sky. Insect larvae, mesofauna, and other organisms colonize the waterbodies and feed on the accumulating detritus. Water‐filled tree holes are not only important habitats for these species but have been used as model systems in ecology. Here, we review more than 100 years of research on tree‐hole inhabiting organisms and show that most studies focus on selected or even single species (most of which are mosquitoes), whereas only few studies examine groups other than insects, especially in the tropics. Using a vote counting of results and a meta‐analysis of community studies, we show that the effects of tree‐hole size and resources on abundance and richness were investigated most frequently. Both were found to have a positive effect, but effect sizes were modulated by site‐specific environmental variables such as temperature or precipitation. We also show that parameters such as the height of the tree holes above ground, tree‐hole density, predation, and detritus type can be important drivers of organism abundance or richness but are less often tested. We identify several important research gaps and potential avenues for future research. Specifically, future studies should investigate the structure, functions, and temporal dynamics of tree‐hole food webs and their cross‐system interactions, for example, with terrestrial predators that act as a connection to their terrestrial surroundings in meta‐ecosystems. Global observational or experimental tree‐hole studies could contribute pivotal information on spatial variation of community structure and environmental drivers of community assembly. With a better understanding of these unique aquatic habitats in terrestrial ecosystems, natural and artificial tree holes can not only serve as model systems for addressing fundamental ecological questions but also serve as indicator systems of the impacts of environmental change on ecosystems. [ABSTRACT FROM AUTHOR]

Cyanobacterial dominance or blooms can influence ecosystem structure in reservoirs, yet there are only few studies of its effect on the resource use and trophic structure of zooplankton. We hypothesised that zooplankton traits would exhibit a strong response to the increase of invasive and toxic cyanobacteria.We investigated the effect of an invasive bloom‐forming cyanobacterium Raphidiopsis raciborskii (formerly Cylindrospermopsis raciborskii) on zooplankton functional traits (e.g., growth, reproduction, allochthonous resource use and realised niche) through laboratory experiments and 3‐year field investigations in two subtropical reservoirs. The realised niche (i.e., resource and habitat use) was quantified using stable isotopes (termed isotopic niches).We fed the cladoceran zooplankton Moina sp. with Scenedesmus obliquus (chlorophyte), R. raciborskii, and a mixture of S. obliquus and R. raciborskii in laboratory experiments. A diet of R. raciborskii alone depressed the growth and reproduction of Moina sp. compared to a diet of S. obliquus alone, but a mixture of S. obliquus and R. raciborskii greatly alleviated the inhibition effects caused by cyanobacteria.Under natural field conditions, we did not find a strong inhibition effect of R. raciborskii dominance on the zooplankton, but a high biomass of R. raciborskii was associated with an increase (17%) in the relative allochthonous resource (terrestrially derived organic matter) use by cladocerans (but not for copepods), even though the chlorophyll‐a concentration increased from 17 μg/L in the non‐bloom period to 28 μg/L during periods of R. raciborskii dominance or blooms. Furthermore, a high biomass of R. raciborskii increased the contribution of inter‐taxa variation (taxa sorting) to the expanded isotopic niches of the zooplankton community.Our study helps to clarify cyanobacteria‐zooplankton interactions and highlights the importance of cyanobacterial dominance or blooms in regulating cross‐ecosystem resource use and biogeochemical cycling mediated by zooplankton in aquatic ecosystems. [ABSTRACT FROM AUTHOR]

The propagule sizes of these green seaweeds were ca. 3-10 m. Ciliates feeding on seaweed propagules were observed even when other known foods, such as diatoms and phytoflagellates, were available. I Monostroma i propagules measure 5-10 m, swim using flagella, and settle on benthic substrates; these characteristics resemble those of the propagules of many other green seaweed species. Keywords: ciliate; coastal ecosystem; food web; green seaweed; life history; microscopic grazer; population dynamics; propagule survival EN ciliate coastal ecosystem food web green seaweed life history microscopic grazer population dynamics propagule survival 1 5 5 08/03/22 20220801 NES 220801 Seaweeds, such as green (Ulvophyceae), brown (Phaeophyceae), and red (Rhodophyta) macroalgae, are primary producers in coastal ecosystems that fix carbon and release oxygen by photosynthesis, form diverse habitats, and provide food sources for various marine organisms, ranging from protists to vertebrates (Hurd et al., 2014). Although whether propagules of other green, brown, and red seaweeds are grazed by ciliates requires further investigation, propagule grazing by ciliates may be potentially widespread, which could explain the high propagule mortality rate. [Extracted from the article]

Space and time promote variation in network structure by affecting the likelihood of potential interactions. However, little is known about the relative roles of ecological and biogeographical processes in determining how species interactions vary across space and time. Here we study the spatiotemporal variation in predator–prey interaction networks formed by anurans and arthropods and test for the effects of prey availability in determining interaction patterns, information that is often absent and limits the understanding of the determinants of network structure. We found that network dissimilarity between ecoregions and seasons was high and primarily driven by interaction rewiring.We also found that species turnover was positively related to geographical distance. Using a null model approach to disentangle the effect of prey availability on the spatial and temporal variation, we show that differences in prey availability were important in determining the variation in network structure between seasons and among areas. Our study reveals that fluctuations in prey abundance, alongside the limited dispersal abilities of anurans and their prey, may be responsible for the spatial patterns that emerged in our predator–prey metaweb. These findings contribute to our understanding of the assembly rules that maintain biotic processes in metacommunities and highlight the importance of prey availability to the structure of these systems. [ABSTRACT FROM AUTHOR]

Herbivorous macroinvertebrates make up a large fraction of secondary production in wetlands, but little is known about how water flow affects herbivorous macroinvertebrate production. Reintroducing measurable water flow (1–5 cm/s) to the oligotrophic (phosphorus-limited) Everglades has the potential to improve herbivorous macroinvertebrate production by providing a constant low supply of phosphorus (P) to periphyton and improving food quality. This study investigated potential effects of flow-mediated nutrient loading on growth rates of herbivorous grazers, juvenile apple snails (Pomacea maculata). Periphyton was grown on standard substrates, within a landscape-scale flow addition experiment, in two sloughs that received elevated velocities (3–5 cm/s) and two control sloughs. The flowing sloughs produced periphyton with greater biomass, higher concentrations of nutrients, and lower C:P ratios. Snails, in a laboratory setting, gained more than 3.7-fold greater total mass when fed periphyton from flowing sloughs than snails fed periphyton from control sloughs. Water column nutrients were slightly elevated in flowing sloughs, but the amount could not fully explain differences in periphyton nutrients or snail growth. Increasing flow above background conditions improved food quality, which subsequently increased growth rates. Restoring flow has the potential to increase nutrient accessibility that could enhance food webs, but additional study will be needed to determine whether increased growth rates translate into increased standing stocks. [ABSTRACT FROM AUTHOR]

The changes within and between seasons in phytoplankton composition and abundance determine the carbon biomass available for upper levels of the food web. Temporal changes in phytoplankton community and environmental parameters in a port in Puerto Madryn, Southwest Atlantic were analysed. During an annual period (2011–2012), samples of surface seawater were collected approximately monthly. We determined phytoplankton community structure (species composition and abundance) and biomass (determined by carbon content and chlorophyll a (Chl a)). Water temperature, salinity and transparency were measured when sampling the surface water and local meteorological data were considered. The main groups observed were diatoms (Bacillariophyta; the most abundant during the concentration peaks of Chl a), dinoflagellates (Dinophyta) and flagellates, which mainly included species of Cryptophyta and Chlorophyta. Diatoms exhibited blooms in March (summer–autumn) and September (spring), represented by Skeletonema costatum and Pseudo-nitzschia spp. respectively. Dinoflagellates contributed to the highest carbon biomass, with peaks in January (summer) and April (autumn), exemplified by Prorocentrum micans and Scrippsiella acuminata, respectively. Temporal differences in community composition were related to the seasonal changes in temperature, solar irradiance, precipitation, salinity and wind velocity. The environmental conditions seem not only to determine the species composition but also cell size distribution: nanoplanktonic (≤ 20 µm) species dominated mainly during late spring, summer and early winter while microplanktonic species (> 20 µm) during late winter and early spring. Our results showed within-season changes and show that not only Chl a, but also carbon content can be considered, as the former is a biased estimator of phytoplankton biomass. This study provides the first seasonally resolved estimation in the area of the carbon biomass available for upper levels of the food web and a necessary information for future scenarios prediction. HIGHLIGHTS• Two diatom blooms were followed by an increase in dinoflagellate abundance.• Annual environmental conditions drive the phytoplankton community structure.• First seasonally estimation of autotrophic biomass availability for Patagonian trophic web. [ABSTRACT FROM AUTHOR]

Salmon and herring support both land and ocean predators and are critical to ecosystem resilience. Their linkages across land and sea realms make them highly susceptible to human activities, which can have flow-on effects up the food web. We quantify and compare the potential cumulative effects of human-driven pressures on interdependent species in salmon- and herring-linked ecosystems of western Canada using a risk assessment methodology. Adding indirect risks resulted in 68% greater total risks for land species than for direct risk alone, versus 15% for marine species. Inclusion of climate change pressures resulted in the greatest change in risk for low trophic marine species and habitats (greater than 25% increase). Forestry-related pressures accounted for the highest risk to all species and projected management of these pressures resulted in a total reduction of risk across all ecosystem components that was more than 14% greater than management of fisheries pressures. Ignoring land food web linkages and pressures underestimated cumulative risk by more than 40% for salmon and herring. This simple framework can be used to evaluate potential risk of existing human uses and future change to inform immediate management of linked land-sea ecosystems and help species avoid the 'death by a thousand cuts'. This article is part of the theme issue 'Nurturing resilient marine ecosystems'. [ABSTRACT FROM AUTHOR]

Theoretical modeling predicts that both direct and delayed density‐dependence are key factors to generate population cycles. Deciphering density‐dependent processes that lead to variable population growth characterizing different phases of the cycles remains challenging. This is particularly the case for the period of prolonged low densities, which is inherently data deficient. However, demographic analyses based on long‐term capture–mark–recapture datasets can help resolve this question. We relied on a 16‐year (2004–2019) live‐trapping program to analyze the summer demography and movements of a cyclic brown lemming population in the Canadian Arctic. More specifically, we examined if inversely density‐dependent processes could explain why population growth can remain low during the prolonged low phase. We found that the proportion of females in the population was inversely density‐dependent with a strong male‐biased sex ratio at low densities but not at high densities. However, survival of adult females was higher than adult males, but both had lower survival at low densities than at high ones. Distances moved by both adult males and females were density‐dependent, and proportion of females in reproductive condition was weakly density‐dependent as it tended to increase at low density. Individual body condition, measured as monthly change in body mass, was not density‐dependent. Overall, the strong male‐biased sex ratio at very low densities suggests a loss of reproductive potential due to the rarity of females and appears to be the most susceptible demographic factor that could contribute to the prolonged low phase in cyclic brown lemmings. What leads to this sex‐bias in the first place is still unclear, potentially owing to our trapping period limited to the summer, but we suggest that it could be due to high predation rate on breeding females in winter. [ABSTRACT FROM AUTHOR]

The puma Puma concolor is the fourth largest wild felid and the most widespread native terrestrial mammal of the Americas. We synthesised published literature documenting the biotic interactions of pumas, in order to: 1) advance our understanding of the ecological roles pumas play in natural systems, and 2) support strategic decision‐making about conservation investments, public education, and whole‐ecosystem conservation management.We divided puma biotic interactions into five categories: 1) diet and prey regulation, 2) fear effects on prey (including trophic cascades), 3) effects via carrion production, 4) effects on other carnivores, and 5) ecosystem services. We reviewed 162 studies that met our search criteria, which described 543 ecological interactions between pumas and 485 other species.Puma diet and prey regulation was the most common research topic. The geographic distribution of research was highly skewed towards the USA and Canada, and research in Tropical moist forests was underrepresented. We found a steep increase in the number of scientific publications exploring the biotic interactions associated with pumas over time, but publications that reported effect sizes or measured the strength of interactions did not increase as quickly. We noted numerous gaps in our knowledge of puma biotic interactions and found few well‐controlled studies of prey fear effects, trophic cascades, or ecosystem services.We conclude that pumas are influential ecological actors in natural systems and important brokers of energy and nutrients throughout ecosystems in the Western Hemisphere, linking disparate species from many trophic levels. Ultimately, we found evidence for investing in and prioritising the protection and restoration of puma populations to conserve biodiversity in the Americas. [ABSTRACT FROM AUTHOR]

Interactions among living beings are the structuring basis of ecosystems, and studies of networks allow us to identify the patterns and consistency of such interactions. Antagonistic networks reflect the energy flow of communities, and identifying network structure and the biological aspects that influence its stability is crucial to understanding ecosystem functioning. We used antagonistic anuran interactions—predator–prey and host–parasite—to assess structural patterns and to identify the key anuran species structuring these networks. We tested whether anuran body‐size and life‐habit are related to their roles in these networks. We collected individuals of 9 species of anurans from an area of the Atlantic Forest in Brazil and identified their prey and helminth parasites. We used network (modularity, specialization, and nestedness) and centrality metrics (degree, closeness, and betweenness) to identify the role of anuran species in both networks. We then evaluated whether anuran body‐size or life‐habit were related to anuran centrality using generalized linear mixed models. The networks formed specialized interactions in compartments composed by key species from different habits. In our networks, anurans with rheophilic and cryptozoic habit are central in predator‐prey networks, and those with larger body size and arboreal and cryptozoic habit in the host‐parasite network. This study represents a step towards a better understanding of the influential factors that affect the structure of anuran antagonist networks, as well as to recognize the functioning roles of anuran species. [ABSTRACT FROM AUTHOR]

Mites of the genus Rhizoglyphus (Acari: Acaridae) are serious pests of plants belonging to the orders Liliales and Asparagales such as onions, garlic, lilies, and tulips. Their control by synthetic pesticides is becoming problematic as a result of resistance development in these mites and environmental and health issues. New pest control methods thus need to be developed. This review provides an overview of studies related to bulb mite management. Entomopathogenic fungi and generalist predatory mites are prospective agents for biological control of these pests while entomopathogenic nematodes and the metabolites of their symbiotic bacteria seems to be less effective. There are, however, many more organisms in the soil that might play important roles in biological control of bulb mites as well as other soil pests of these bulbous plants. Therefore, a holistic approach based on the understanding of food webs in the soil environment and their ecological services is essential for developing effective control of bulb mites. For the rehabilitation and conservation of soil biodiversity supporting these ecosystem services, emphasis must be placed on sustainable soil management (e.g., ensuring green coverage, minimal soil disturbance and high content of organic matter). [ABSTRACT FROM AUTHOR]

Parasites are ubiquitous and constitute a substantial amount of natural biomass. Host species differ greatly in how many parasite species they harbor. In this idea paper, we ask what may cause the distribution of parasite diversity in an ecosystem. Since host species interact trophically in a food web and parasites are often transmitted along trophic links, we argue that trophic transmission can be a potential mechanism for explaining parasite diversity distribution. We propose a modeling framework for investigating this issue. The feasibility of our idea is demonstrated by fitting a simulation model to data derived from the Carpinteria ecosystem. Our preliminary analysis suggests that a model with trophic transmission is able to produce parasite diversity distribution similar to the empirical data better than a model without trophic transmission can. We also discuss possible extensions of our preliminary work for future research. [ABSTRACT FROM AUTHOR]

Agricultural practice has led to landscape simplification and biodiversity decline, yet recently, energy‐producing infrastructures, such as wind turbines, have been added to these simplified agroecosystems, turning them into multi‐functional energy‐agroecosystems. Here, we studied the trophic interactions of bats killed at wind turbines using a DNA metabarcoding approach to shed light on how turbine‐related bat fatalities may possibly affect local habitats. Specifically, we identified insect DNA in the stomachs of common noctule bats (Nyctalus noctula) killed by wind turbines in Germany to infer in which habitats these bats hunted. Common noctule bats consumed a wide variety of insects from different habitats, ranging from aquatic to terrestrial ecosystems (e.g., wetlands, farmland, forests, and grasslands). Agricultural and silvicultural pest insects made up about 20% of insect species consumed by the studied bats. Our study suggests that the potential damage of wind energy production goes beyond the loss of bats and the decline of bat populations. Bat fatalities at wind turbines may lead to the loss of trophic interactions and ecosystem services provided by bats, which may add to the functional simplification and impaired crop production, respectively, in multi‐functional ecosystems. [ABSTRACT FROM AUTHOR]

Historical mining left a legacy of abandoned mines and waste rock in remote headwaters of major river systems in the western United States. Understanding the influence of these legacy mines on culturally and ecologically important downstream ecosystems is not always straightforward because of elevated natural levels of mineralization in mining‐impacted watersheds. To test the ecological effects of historic mining in the headwaters of the upper Salmon River watershed in Idaho (USA), we measured multiple community and chemical endpoints in downstream linked aquatic–terrestrial food webs. Mining inputs impacted downstream food webs through increased mercury accumulation and decreased insect biodiversity. Total mercury (THg) in seston, aquatic insect larvae, adult aquatic insects, riparian spiders, and fish at sites up to 7.6 km downstream of mining was found at much higher concentrations (1.3–11.3‐fold) and was isotopically distinct compared with sites immediately upstream of mining inputs. Methylmercury concentrations in bull trout and riparian spiders were sufficiently high (732–918 and 347–1140 ng MeHg g−1 dry wt, respectively) to affect humans, birds, and piscivorous fish. Furthermore, the alpha‐diversity of benthic insects was locally depressed by 12%–20% within 4.3–5.7 km downstream from the mine. However, because total insect biomass was not affected by mine inputs, the mass of mercury in benthic insects at a site (i.e., ng Hg m−2) was extremely elevated downstream (10–1778‐fold) compared with directly upstream of mining inputs. Downstream adult aquatic insect–mediated fluxes of THg were also high (~16 ng THg m−2 day−1). Abandoned mines can have ecologically important effects on downstream communities, including reduced biodiversity and increased mercury flux to higher order consumers, including fish, birds, and humans. Environ Toxicol Chem 2022;41:1696–1710. Published 2022. This article is a U.S. Government work and is in the public domain in the USA. [ABSTRACT FROM AUTHOR]

Food ontologies are acquiring a central role in human nutrition, providing a standardized terminology for a proper description of intervention and observational trials. In addition to bioactive molecules, several fermented foods, particularly dairy products, provide the host with live microorganisms, thus carrying potential "genetic/functional" nutrients. To date, a proper ontology to structure and formalize the concepts used to describe fermented foods is lacking. Here we describe a semantic representation of concepts revolving around what consuming fermented foods entails, both from a technological and health point of view, focusing actions on kefir and Parmigiano Reggiano, as representatives of fresh and ripened dairy products. We included concepts related to the connection of specific microbial taxa to the dairy fermentation process, demonstrating the potential of ontologies to formalize the various gene pathways involved in raw ingredient transformation, connect them to resulting metabolites, and finally to their consequences on the fermented product, including technological, health and sensory aspects. Our work marks an improvement in the ambition of creating a harmonized semantic model for integrating different aspects of modern nutritional science. Such a model, besides formalizing a multifaceted knowledge, will be pivotal for a rich annotation of data in public repositories, as a prerequisite to generalized meta-analysis. [ABSTRACT FROM AUTHOR]

Extreme habitats often harbor specific communities that differ substantially from non-extreme habitats. In many cases, these communities are characterized by archaea, bacteria and protists, whereas the number of species of metazoa and higher plants is relatively low. In extremely acidic habitats, mostly prokaryotes and protists thrive, and only very few metazoa thrive, for example, rotifers. Since many studies have investigated the physiology and ecology of individual species, there is still a gap in research on direct, trophic interactions among extremophiles. To fill this gap, we experimentally studied the trophic interactions between a predatory protist (Actinophrys sol, Heliozoa) and its prey, the rotifers Elosa woralli and Cephalodella sp., the ciliate Urosomoida sp. and the mixotrophic protist Chlamydomonas acidophila (a green phytoflagellate, Chlorophyta). We found substantial predation pressure on all animal prey. High densities of Chlamydomonas acidophila reduced the predation impact on the rotifers by interfering with the feeding behaviour of A. sol. These trophic relations represent a natural case of intraguild predation, with Chlamydomonas acidophila being the common prey and the rotifers/ciliate and A. sol being the intraguild prey and predator, respectively. We further studied this intraguild predation along a resource gradient using Cephalodella sp. as the intraguild prey. The interactions among the three species led to an increase in relative rotifer abundance with increasing resource (Chlamydomonas) densities. By applying a series of laboratory experiments, we revealed the complexity of trophic interactions within a natural extremophilic community. [ABSTRACT FROM AUTHOR]

Fisheries ecosystem-based management is an important tool for sustainable harvesting of fisheries worldwide. Knowledge of trophic interactions is crucial since changes in trophic balances can induce severe changes in the structure of marine communities. While advocated for deep-sea fisheries, a lack of studies in the benthopelagic area persist. The Antarctic toothfish, Dissostichus mawsoni, is a top predator inhabiting the Southern Ocean deep-sea and a high-value species in a fishery managed by CCAMLR (Commission for the Conservation of Antarctic Marine Living Resources). Previous studies suggested a geographical variability in its diet, but never studying it in the same year. We analysed stomach contents and stable isotopes of δ15N and δ13C in the muscle of D. mawsoni captured in three fishing areas from the Amundsen and Dumont D'Urville Seas, during the 2016/17 fishing season. Although significant spatial differences were found, five taxa were found in all sites, Antimora rostrata, Macrourus spp., Muraenolepis spp., Moroteuthopsis longimana and Psychroteuthis glacialis. High diversity of prey confirms D. mawsoni as a generalist feeder. Values of δ15N showed similar trophic position across areas, in contrast to the differences found in δ13C values. GLM showed that δ15N and δ13C values varied with otolith length, latitude and the opposite isotope, i.e. δ13C and δ15N respectively. Implications for D. mawsoni fisheries management are discussed considering different predation release scenarios. [ABSTRACT FROM AUTHOR]

Noctiluca scintillans is a heterotrophic dinoflagellate that causes red-colored oceans during the day (red tides) and glowing oceans at night (bioluminescence). This species feeds on diverse prey, including phytoplankton, heterotrophic protists, and eggs of metazoans. Thus, many scientists have conducted studies on the ecophysiology of this species. It is easy to cultivate N. scintillans at a scale of <1 L, but it is difficult to cultivate them at a scale of >100 L because N. scintillans cells usually stay near the surface, while prey cells stay below the surface in large water tanks. To obtain mass-cultured N. scintillans cells, we developed an automatic system for cultivating N. scintillans on a scale of 100 L. The system consisted of four tanks containing fresh nutrients, the chlorophyte Dunaliella salina as prey, N. scintillans for growth, and N. scintillans for storage, respectively. The light intensities supporting the high growth rates of D. salina and N. scintillans were 300 and 20 µmol photons m-2 s-1, respectively. Twenty liters of D. salina culture from the prey culture tank were transferred to the predator culture tank, and subsequently 20 L of nutrients from the nutrient tank were transferred to the prey culture tank every 2 d. When the volume of N. scintillans in the predator culture tank reached 90 L 6 d later, 70 L of the culture were transferred to the predator storage tank. To prevent N. scintillans cells from being separated from D. salina cells in the predator culture tank, the culture was mixed using an air pump, a sparger, and a stirrer. The highest abundance of N. scintillans in the predator culture tank was 45 cells mL-1, which was more than twice the highest abundance when this dinoflagellate was cultivated manually. This automatic system supplies 100 L of N. scintillans pure culture with a high density every 10 d for diverse experiments on N. scintillans. [ABSTRACT FROM AUTHOR]

Species introductions are common in freshwater environments and have the potential to transform community and ecosystem structure. Predatory centrarchid fishes and American Bullfrogs (Lithobates catesbeianus Shaw, 1802 previously Rana catesbeiana) are both widespread aquatic invaders implicated in native amphibian declines. In lowland ecosystems, co-occurrence between native and nonnative amphibian and fish taxa is common; however, the mechanisms that facilitate their co-occurrence are poorly studied. Stable isotope analysis offers a tool to examine trophic interactions among native and nonnative taxa, including predation, competition, and shifting food resource availability, which may provide mechanistic insight into the drivers of co-occurrence. In this study, we used stable isotopes (δ13C and δ15N) to determine how the trophic structure of native fishes and amphibians differs between waterbodies with and without nonnative centrarchid fishes and bullfrogs across a floodplain in southwestern Washington, USA. We hypothesized that native species alter their feeding strategies to reduce niche overlap with nonnative taxa. In the presence of nonnative taxa, Three-spine Stickleback (Gasterosteus aculeatus Linnaeus, 1758), all native larval salamander species (Ambystoma gracile Baird, 1859 and Ambystoma macrodactylum Baird, 1850), and 1 of 2 native larval frog species (Rana aurora Baird and Girard, 1852) exhibited shifts in food resources or trophic position. Despite trophic differences, only 1 species (A. macrodactylum) had a smaller niche size in the presence of nonnatives. The observed trophic shifts reflect changes in habitat or food resources, which may reduce competition or predation and promote co-occurrence between nonnative and native taxa. Our results suggest that the co-occurrence of native and nonnative amphibians and fishes in lowland floodplain habitats may be facilitated by a broad range of food resources and complex habitat structure. [ABSTRACT FROM AUTHOR]

Predators compete aggressively for resources, establishing trophic hierarchies that influence ecosystem structure. Competitive interactions are particularly important in invaded ecosystems where introduced predators can suppress native prey species. We investigated whether niche partitioning exists within a guild of invasive mammalian predators and determined the consequences for native species. Over 4405 camera‐trap days, we assessed interactions among three invasive predators: two apex predators (feral cats Felis catus and ferrets Mustela furo) and a mesopredator (stoats Mustela erminea), in relation to their primary prey (lagomorphs, rodents and birds) and habitat use. Further, we tested for mesopredator release by selectively removing cats and ferrets in a pulse perturbation experiment. We found compelling evidence of niche partitioning; spatiotemporal activity of apex predators maximized access to abundant invasive prey, with ferrets targeting lagomorphs and cats targeting rodents. Mesopredators adjusted their behavior to reduce the risk of interference competition, thereby restricting access to abundant prey but increasing predation pressure on diurnal native birds. Stoats were only recorded at the treatment site after both larger predators were removed, becoming the most frequently detected predator at 6 months post‐perturbation. We suggest there is spatial and resource partitioning within the invasive predator guild, but that this is incomplete, and avoidance is achieved by temporal partitioning within overlapping areas. Niche partitioning among invasive predators facilitates coexistence, but simultaneously intensifies predation pressure on vulnerable native species. [ABSTRACT FROM AUTHOR]

Since the arrival of the invasive quagga mussels Dreissena rostriformis bugensis in Lake Constance, significant changes in the zooplankton and benthic invertebrate community were observed. Five years later the quagga mussel has become the dominating species of the benthic community. Its effects on other components of the food web, especially those at higher trophic levels such as fish, remain unclear around the world. To evaluate the actual impact of quaggas on the local food web of Lake Constance, the stable isotope compositions of pelagic whitefish and different benthic fish species from before and after the quagga invasion were compared. A significant increase in δ13C was detected in pelagic whitefish one year after the establishment of the quagga mussel in the lake. This change was most likely the consequence of an increase in benthic-derived nearshore primary production and a shift towards more littoral feeding, than a change in dietary composition. Stomach content analysis of contemporary samples revealed that pelagic whitefish (Coregonus wartmanni) still feed exclusively on pelagic zooplankton. In contrast, benthic whitefish (Coregonus macrophthalmus), roach (Rutilus rutilus) and tench (Tinca tinca) show today high levels of quagga consumption. However, this behaviour alone could not explain the observed differences in δ15N from periods before and after the quagga invasion. The results suggest that energy sources and pathways have changed considerably for both pelagic and benthic dwelling fish species in Lake Constance following the establishment of quaggas. [ABSTRACT FROM AUTHOR]

The addition of trace contaminants to surface waters is recognized as a rising environmental concern and caffeine is among those most commonly detected. Classic toxicological analyses of single organisms have described some of the impacts of caffeine on freshwater organisms, but few have examined ecological interactions, food webs, or aquatic‐terrestrial linkages, especially in natural aquatic systems. This study used an in situ manipulative experiment to effects of caffeine addition on aquatic biofilms and biomass of aquatic and emergent insects. We used chemical diffusing substrata to introduce small concentrations of caffeine to streams and analyzed effects on downstream biofilm nutrient content, benthic macroinvertebrates, and emergent insects. We found that caffeine addition decreased the biomass of emergent insects by 56% and altered biofilm nutrient content in complex ways that interact with canopy cover, with stronger effects of caffeine addition under low canopy cover (higher light). Thus, the impacts of this common aquatic contaminant may influence the linked riparian food web by decreasing emergent insects, an important food source for riparian insectivores. [ABSTRACT FROM AUTHOR]

Predation affects community structure and functioning within marine habitats. Predator–prey interactions can change through space and time. Documenting how these interactions change is essential to improve our understanding of food web dynamics and to enhance our ability to manage preferred species. In this study, our goals were to determine whether the density of subtidal oysters (Crassostrea virginica) differed spatially by looking at three separate restored oyster sanctuaries within Pamlico Sound (North Carolina, USA), whether oyster density changed over an interval of 16 months, and whether oyster density was related to the presence of different‐sized predators by using an experimental approach. Multiple exclusion treatments were used in situ to exclude, selectively, different predator guilds from consuming oysters. Predator densities were also measured both within experimental treatments and on the restored oyster reefs by using multiple survey techniques. We found that oyster abundance differed among the four sample dates over the 16‐month study and differed among the three sites. Mud crabs—one of the smallest predators measured—had the greatest predator biomass per unit of area, but the presence of other predators was largely site‐dependent. Oyster abundance was affected by the exclusion of all predators, but this was dependent on sample date and location, which may suggest that mud crabs were the only predator to reduce oyster abundance in this study. In addition, large predators may have affected small predators, such as mud crabs and oyster drills, which were more abundant in treatments where large predators were excluded. The strongest evidence for top‐down effects on oyster reefs occurred at one of the three field sites at the first and final sampling time, suggesting that predator effects are complex, as well as spatially and temporally variable. Field experiments that assess variables through time and at multiple locations are needed as this information could improve the success of oyster reef conservation and restoration efforts. [ABSTRACT FROM AUTHOR]

Abstract Current understanding on the exposure of freshwater organisms to microplastics (plastics sized between 1 µm and 5 mm) has arisen mostly from laboratory experiments—often conducted under artificial circumstances and with unrealistic concentrations. In order to improve scientific links through real ecosystem exposure, we review field data on the exposure of free‐living organisms to microplastics. We highlight that the main outputs provided by field research are an assessment of the occurrence and, at times, the quantification of microplastics in different animal taxa. Topics of investigation also include the causes of contamination and the development of biological monitoring tools. With regard to taxa, fish, mollusks, and arthropods are at the center of the research, but birds and amphibians are also investigated. The ingestion or occurrence of microplastics in organs and tissues, such as livers and muscles, are the main data obtained. Microorganisms are studied differently than other taxa, highlighting interesting aspects on the freshwater plastisphere, for example, related to the structure and functionality of communities. Many taxa, that is, mammals, reptiles, and plants, are still under‐examined with regard to exposure to microplastics; this is surprising as they are generally endangered. As biota contamination is acknowledged, we contribute to an interdisciplinary scientific discussion aimed at a better assessment of knowledge gaps on methodology, impact assessment, and monitoring.

Abstract Scavenging can have important consequences for food web dynamics, for example, it may support additional consumer species and affect predation on live prey. Still, few food web models include scavenging. We develop a dynamic model that includes two facultative scavenger species, which we refer to as the predator or scavenger species according to their natural scavenging propensity, as well as live prey, and a carrion pool to show ramifications of scavenging for predation in simple food webs. Our modeling suggests that the presence of scavengers can both increase and decrease predator kill rates and overall predation in model food webs and the impact varies (in magnitude and direction) with context. In particular, we explore the impact of the amount of dynamics (exploitative competition) allowed in the predator, scavenger, and prey populations as well as the direction and magnitude of interference competition between predators and scavengers. One fundamental prediction is that scavengers most likely increase predator kill rates, especially if there are exploitative feedback effects on the prey or carrion resources like is normally observed in natural systems. Scavengers only have minimal effects on predator kill rate when predator, scavenger, and prey abundances are kept constant by management. In such controlled systems, interference competition can greatly affect the interactions in contrast to more natural systems, with an increase in interference competition leading to a decrease in predator kill rate. Our study adds to studies that show that the presence of predators affects scavenger behavior, vital rates, and food web structure, by showing that scavengers impact predator kill rates through multiple mechanisms, and therefore indicating that scavenging and predation patterns are tightly intertwined. We provide a road map to the different theoretical outcomes and their support from different empirical studies on vertebrate guilds to provide guidance in wildlife management.

Climate change is having myriad effects on Arctic marine ecosystems and food webs. Anadromous Arctic Char, Salvelinus alpinus (Linnaeus, 1758), feed intensively at sea during summer. In Cumberland Sound, Nunavut, Canada, there has been a recent increased availability of a forage fish, Capelin. To investigate changes over time in Arctic Char foraging, we assessed Arctic Char trophic niche from 2002 to 2011 using stomach content analysis and stable isotope analysis (δ13C and δ15N) of muscle tissue from two river/lake systems, Isuituq and Kipisa. We also compared population characteristics by calculating Fulton’s condition factor (K) and by fitting von Bertalanffy growth curves with length-at-age data. Results revealed Capelin were newly present in the diets of Arctic Char in 2011, describing a shift from a primarily invertebrate-based to a fish-based diet. No trend in δ15N over time suggests that the trophic level of Arctic Char has not changed; however, the δ15C for both systems converged in 2011 on a value suggestive of feeding on Capelin. Growth curves and length-at-age analyses suggest that foraging on Capelin may have increased individual growth. Changes in the growth and condition of Arctic Char in this region could have significant economic and cultural implications.

Submarine emissions of gases from hydrothermal vents alter the surrounding chemical environment, influencing species responses to the resulting environmental gradients. The 2011 underwater eruption of the Tagoro volcano off the coast of El Hierro in the Atlantic Ocean changed the physical and chemical conditions, impacting the distribution of pelagic fauna. Post-eruptive stages from 2013 to 2018 revealed changes in both benthic and pelagic communities, with continuous eruptions further affecting local carbon cycle through shifts in nutrient concentrations and isotopic composition. The lowest δ13C values in zooplanktonic primary consumers were found in areas directly influenced by the Tagoro submarine volcano. Although the mixing model results show that phytoplankton is the primary carbon source for copepods, contributing an average of 28.3% of their carbon, magmatic CO 2 and seawater dissolved inorganic carbon each account for approximately 17–18%. The isotopic signatures reveal a gradient of enrichment in copepods, reflecting the influence of inorganic nutrient and gas emissions from the volcano's centre to its periphery within the marine ecosystem. This data is useful for understanding the worldwide significance of environmental stressors such as volcanic eruptions on marine organisms. • Zooplankton community of the volcano dominated by copepods and chaetognaths. • Chaetognaths correspond to a higher trophic level than copepods. • Isotopes revealed variation of the carbon source in the copepods. • Consistent decrease δ13C with increasing proximity to the submarine emissions. [ABSTRACT FROM AUTHOR]

Space-for-time substitution, also known as pseudo chronosequence (PCS), is often used as a method to assess temporal changes in ecosystems without having to wait for the time span that the study is supposed to cover. However, the suitability of PCS studies is often questioned because convergent development of spatially separated plots over time is rarely guaranteed even under optimal conditions. To assess whether the PCS approach is justified and suitable, we studied the nematode soil food web development of free-living nematodes and biological and chemical soil components related to C and N mobilization (CO 2 and NO 3 -) and immobilization (microbial and soil organic carbon), in a PCS focusing on the critical early reclamation period of four years after open-cast lignite mining, and compared it with a real chronosequence (RCS) of a reclamation site monitored over four years. We hypothesized that: (I) nematode-derived indices indicate the same course of nematode soil food web development in the PCS and RCS, tolerating a range of variability in weather conditions, soil components, and management; (II) the development of nematode soil food web indicators can provide information on the status of C and N retention and cycling in the reclaimed soil. Our results show that the PCS and RCS approaches reach similar conclusions, indicating a rapidly developing nematode soil food web during the first four years after reclamation. They also suggest that the nematode faunal profile may indicate the status of C and N retention and cycling in reclaimed soil. Overall, it can be concluded that the PCS approach successfully predicts the temporal development of the nematode soil food web in loess-dominated reclaimed mining soils, even when there is a range of variability in soil components and management conditions. • Pseudo and real chronosequence showed similar food web developments in reclaimed soil. • Chronosequence conclusions were not confounded by natural and management variation. • Nematode faunal profile may indicate C and N retention and cycling status in reclaimed soil. [ABSTRACT FROM AUTHOR]

In order to understand the transfer of macroelements and toxic metals in the terrestrial food web, barn swallows, terrestrial frogs, and insects were collected from farmlands in the Leizhou Peninsula, and analyzed for macroelements carbon (C), nitrogen (N), phosphorus (P), and sulfur (S) and trace metals nickel (Ni), zinc (Zn), selenium (Se), copper (Cu), chromium (Cr), cadmium (Cd), lead (Pb), and mercury (Hg). The multi-element ecological stoichiometry was discussed to trace the food web flow of nutrients and toxicants. The percentage contents of C, N, P, and S were 35.43–59.91%, 6.89–12.11%, 0.49–4.66%, and 0.44–2.19%, respectively. The concentrations of Ni, Zn, Se, Cu, Cr, Cd, Pb, and Hg were 0.163–116 mg/kg, 38.7–227 mg/kg, 0.0453–3.82 mg/kg, 3.11–141 mg/kg, not detected—79.6 mg/kg, 0.0203–0.358 mg/kg, 0.148–4.57 mg/kg, and 0.00159–1.46 mg/kg, respectively. Organisms at high trophic levels had higher contents of N, P, and S, and lower contents of C. Significant correlations were observed between δ15N and ratios of C: N, C: P, C: S, N: P, N: S, and S: P, indicating selective transfer of biogenic elements for predators in the terrestrial food web. Most metals including Ni, Zn, Se, Cu, Cr, Pb, and Hg had biomagnification factors and trophic magnification factors higher than 1, because the whole body of organisms rather than tissues were used. The negative correlations between the detoxification ratios of Se: X (each toxic metal) and metal concentrations suggest potential adverse effect of metals on terrestrial organisms. [Display omitted] • Terrestrial predators at higher trophic levels have higher demand for N, P, and S. • All eight heavy metals except Cd biomagnified in this terrestrial food web. • The risk of metals may be underestimated by using individual tissues for predators. • Se showed potential detoxification of most metals in this terrestrial food web. [ABSTRACT FROM AUTHOR]

The trophic cascade has emerged as a key paradigm in ecology. Although ecologists have made progress in understanding spatial variation in the strength of trophic cascades, temporal variation remains relatively unexplored. Our review suggests that strong trophic cascades are often transient, appearing when ecological conditions support high consumer abundance and rapidly growing, highly edible prey. Persistent top-down control is expected to decay over time in the absence of external drivers, as strong top-down control favors the emergence of better-defended resources. Temporal shifts in cascade strength-including those driven by contemporary global change-can either stabilize or destabilize ecological communities. We suggest that a more temporally explicit approach can improve our ability to explain the drivers of trophic cascades and predict the impact of changing cascade strength on community dynamics.

Introduced predators can have dramatic effects on island ecosystems, the magnitude of which are likely to vary with island characteristics. We investigated the influence of two important properties of islands-size and amount of resource subsidy-on the effects of an introduced predatory lizard (Anolis sagrei) on three groups of arthropod prey. Lizards were experimentally introduced to 16 islands that spanned gradients in vegetated area and seaweed deposition (a marine resource subsidy); 16 similar islands served as lizard-free controls. The abundance of web spiders, salticid spiders, and wasps was estimated prior to lizard introduction and again four months after lizard introduction. Lizard introduction reduced the average abundance of all three groups of arthropods. The effect of lizards on salticid spiders- which was very large (94% reduction in salticid abundance)-decreased with island size. In contrast, the effect of lizards on wasps-which was also very large (88% reduction in wasp abundance)-tended to increase with island size, but with only marginal significance. There was no evidence for variation in the effect of lizards on web spiders with island size. This variation between prey taxa may be related to the relative importance of environmental stress (such as wind and wave exposure, which tend to be more pronounced on smaller islands) in determining abundance. Salticids seem to tolerate the stressful environmental conditions that characterize smaller islands, allowing for larger lizard effects; wasps seem to be limited by these conditions (either directly or indirectly via reduced prey availability), minimizing lizard effects on smaller islands. There was a marginally significant tendency for the effect of lizards on salticid spiders to be weaker on islands with more seaweed deposition, suggesting that subsidies may play a role in reducing predator effects on islands. Our results highlight the importance of ecological context in determining the top-down effects of introduced predators and underscore the need to extend existing theories relating island area and community characteristics toward an explicit consideration of species interactions.

The effects of microbial biopesticides used for mosquito control on autotrophic microorganisms such as nanophytoplankton are equivocal. We examined impacts of mosquito biopesticides and mosquito larvae on primary producers in two independent experiments. In the first experiment, we examined the effects of a commonly used microbial biopesticide formulation (VectoMax® CG) on a unicellular microalga, Selenastrum capricornatum Printz, under axenic laboratory conditions. The biopesticide treatments included two concentrations (0.008 and 0.016 g liter-1 ) of VectoMax® CG and two controls (one untreated and another with autoclaved 0.016 g VectoMax® CG liter-1 ) in replicated axenic experimental microcosms. Spectrophotometric analysis of chlorophyll a (proxy for algal biomass) and direct enumeration of algal cells following the treatments revealed no significant effects of the microbial biopesticide on algal population growth during the four-week study. In the second experiment, we tested the effects of different densities of Culex larvae on the population of S. capricornatum. Effects of mosquito larvae feeding on S. capricornatum were significant with a curvilinear relationship between larval density and algal abundance in the water column. Together, these studies demonstrated a lack of direct cytological/toxicological effects of Bacillus-based microbial pesticides on freshwater primary production and support the hypothesis that the reduction in algal primary production previously reported when Bti products were applied to aquatic environments was likely independent of the Bacillus-based larvicidal toxins. Instead, it was likely mediated by microbial interactions in the water column and the trophic cascade effects that resulted from the removal of larval mosquitoes. These studies suggest that mosquito larvae independent of pesticide application can influence primary production. Our method of evaluating biopesticides against small photoautotrophs can be very useful for studying the unintended effects on autotrophic microorganisms of other pesticides, including herbicides and pesticides applied to aquatic environments.

Through the fixation of large quantities of dissolved inorganic carbon (DIC), macroalgae facilitate the energetic foundation of highly productive coastal ecosystems. While the processes controlling photosynthesis and carbon fixation by macroalgae are well known, the fate of organic matter fixed by macroalgae is less well understood. This study quantified release rates of DOC by three ecologically significant Baltic macroalgae species: the perennial habitat forming Fucus vesiculosus and Furcellaria lumbricalis, and the seasonal fast-growing Ulva intestinalis, under both light and dark conditions. The released products were assessed using bacterial incubations whereby radiolabeled leucine was used to evaluate the uptake and lability of these products by marine heterotrophic bacteria. DOC was found to be released by both F. vesiculosus and U. intestinalis at rates of 0.27 mg C·h−1 under light and 0.13 mg C·h−1 per unit of dry mass under dark treatments, respectively, whereas F. lumbricalis DOC release was observed to be negligible under both light and dark. Our findings further validate previous hypotheses that factors such as photosynthetic activity are a primary driver behind DOC release and that DOC release is not an entirely passive process. Additionally, we reaffirm the need to relate a given species life characteristics and habitat in order to understand why DOC products are released. The consumption of macroalgae-derived DOC by heterotrophic bacteria reveals that released DOC is variable in its lability. After a period of 12 h and under maximum photosynthetic conditions, the release of DOC by F. vesiculosus and U. intestinalis achieved a peak rate of 219 µg C·L−1·day−1 and 214 µg C·L−1·day−1 for each gram of dry weight material, respectively, directly into the microbial loop via heterotrophic bacterial consumption. In contrast, F. lumbricalis’ low rate of DOC release and the subsequent low bacterial consumption indicate that habitats dominated by this species have a reduced importance in the transfer energy via the microbial loop. These findings have implications for how we view carbon transfer within coastal food webs and highlight how changes in species composition and coverage may dramatically affect coastal ecosystem productivity through the microbial loop.

Benthic communities below the photic zone are largely reliant on the export of surface-water primary production and the flux of partially degraded organic matter to the seabed, i.e. pelagic−benthic coupling. Over the past decades, however, the role of chemosynthetically produced carbon in food webs has been recognized in various habitats. Cold seeps are now known to be widespread across circumpolar Arctic shelves where natural release of hydrocarbons occurs at the seabed. Here, we investigated to what extent chemosynthesis-based carbon (CBC) enters the food web in a high latitude shelf-system. Specifically, we estimated the contributions of chemosynthesis-based carbon to primarily benthic invertebrate taxa from seeps at both shallow and deeper shelves and comparative non-seep areas in the Svalbard-Barents Sea region using bulk stable isotope-analysis of carbon and nitrogen. Our results show low δ13C values (-51.3 to -32.7 ‰) in chemosymbiotic siboglinids and several species of benthic, higher-trophic level, invertebrates (mainly polychaetes and echinoderms; -35.0 to -26.1‰) collected at cold seeps, consistent with assimilation of chemosynthesis-based carbon into the Arctic benthic food web. Using a two-component mixing equation, we demonstrate that certain species could derive more than 50% of their carbon from chemosynthesis-based carbon. These findings show that autochthonous chemosynthetic energy sources can contribute to supporting distinct groups of ‘background’ benthic taxa at these Arctic seep-habitats beyond microbial associations and chemosymbiotic species. Furthermore, we found a higher degree of chemosynthesis-based carbon in benthos at the deeper Barents Sea shelf seeps (>330 m) compared to seeps at the Western Svalbard shelf (

This article reviews the nature of functional responses that have commonly been used to represent feeding relationships in the ecological literature. It compares these with the range of functional response forms that are likely to characterize species in natural communities. The latter set of responses involves many more variables. The article reviews the history of functional response models, and examines previous work that has allowed the functional response of a predator to a single type of prey to depend on additional variables beyond the abundance of that prey type. While a number of more complex functional responses have been discussed over the years, many variables affecting feeding rates are still typically omitted from models of food webs. The influences on functional responses from trophic levels above that of the predator or below that of the prey are particularly likely to be ignored, although models and data have suggested that they can have large effects on the functional response. The influences of adaptive behavior and of the time-scale of response measurement are also too often ignored. Some of the known and unknown consequences of these omissions are discussed.

As amplified by climate changes and anthropogenic activities, mobile generalist species have been dominating the food web succession in a closed ecosystem. However, compared to marine ecosystem, the internal mechanism of generalist species affecting freshwater community were paid less attentions. In this study, the association of mobile generalist species and native apex predator was identified in Chenghai Lake, where was taken as the study case of a closed ecosystem to create the succession dynamic of food web from 1983 to 2019. Weighted food web analysis (WFWA) approach was applied to determine keystoneness and interaction strength of each species node, which is achieved through the quantification of the direct impacts on food web nodes from its biomass. As shown in the results, in the food web of 1983, there were nearly 25 nodes and 80 links, while in 2009, there were 22 nodes and 58 links, however, in 2019, there were 16 nodes and 25 links. In 2019, the three original specialized apex predator nodes were disappear. The keystoneness of each species was − 0.048, − 0.109 and − 0.742 respectively. During the nearly 40-year succession, including 13 native species had gone within 10 years, which were difficult to find its trace. The omnivorous alien species have occupied an absolute dominant niche, exhibiting the characteristics of mobile generalist species in 2019. The keystoneness of these species was − 0.194, − 0.235 and − 0.236 respectively. In general, from 1983 to 2019, the nodes have decreased by 36% and links have dropped by 68.75% on average in Chenghai Lake food web. In this study, (a)revealing the associations between mobile generalist species and native apex predators; (b) distinguishing the keystone species affecting food web structural; (c) developing food web analysis approach and determining the succession dynamic of Chenghai Lake. These findings improve the understanding of potential impacts from mobile generalist species in closed ecosystem.

Abstract Water‐filled tree holes are unique ecosystems that may occur high up in tree crowns and are essentially aquatic islands in the sky. Insect larvae, mesofauna, and other organisms colonize the waterbodies and feed on the accumulating detritus. Water‐filled tree holes are not only important habitats for these species but have been used as model systems in ecology. Here, we review more than 100 years of research on tree‐hole inhabiting organisms and show that most studies focus on selected or even single species (most of which are mosquitoes), whereas only few studies examine groups other than insects, especially in the tropics. Using a vote counting of results and a meta‐analysis of community studies, we show that the effects of tree‐hole size and resources on abundance and richness were investigated most frequently. Both were found to have a positive effect, but effect sizes were modulated by site‐specific environmental variables such as temperature or precipitation. We also show that parameters such as the height of the tree holes above ground, tree‐hole density, predation, and detritus type can be important drivers of organism abundance or richness but are less often tested. We identify several important research gaps and potential avenues for future research. Specifically, future studies should investigate the structure, functions, and temporal dynamics of tree‐hole food webs and their cross‐system interactions, for example, with terrestrial predators that act as a connection to their terrestrial surroundings in meta‐ecosystems. Global observational or experimental tree‐hole studies could contribute pivotal information on spatial variation of community structure and environmental drivers of community assembly. With a better understanding of these unique aquatic habitats in terrestrial ecosystems, natural and artificial tree holes can not only serve as model systems for addressing fundamental ecological questions but also serve as indicator systems of the impacts of environmental change on ecosystems.

Food web studies rely heavily on the use of traditional gut content analysis or the fairly popular stable isotope analysis rather than fatty acid analysis (FAA) despite its straightforward process, and ability to identify and characterize more diverse trophic pathways. In this study, we employed fatty acid (FA) biomarkers as a preliminary attempt to trace and characterize trophic pathways in food webs of four tropical lakes of volcanic origin in Luzon Island, Philippines - three clustered maar lakes (Yambo, Pandin and Calibato) and a large caldera lake (Taal). These lakes have a long history of human disturbance but limited ecological data. Knowledge of basal food sources and existing trophic dynamics of organisms are generally non-existent. Particulate organic matter (POM), zooplankton, and fish species were collected in August 2019 from the study lakes as representative of three trophic guilds. Non-metric multidimensional scaling (NMDS) and principal component analysis (PCA) were conducted to analyse FA profiles and characterize trophic relationships between representative organisms. For the POM, within lakes comparison of taxon-specific FA profiles showed a significant difference between the surface and near bottom depths, with the former dominated by photoautorophs and the latter by chemotrophs, suggesting the ability of FAA to effectively delineate between micro-organisms. Between lakes comparison also showed significant difference between the caldera and maar lakes, with the latter containing higher composition of bacterial FA, reminiscent of the considerably smaller lakes’ response to the impact of unmitigated organic loadings from anthropogenic activities. Taken together with the primary consumers’ FA profiles, analysis confirmed the ability of FAA to discriminate between FA profile sources. PCA explained >70% of the variance in the FA compositions for three trophic guilds in the two deepest lakes, which delineated both zooplankton and fish species food selectivity in each lake, alluding to FAA’s capacity to characterize dietary reliance of various species in an environment with numerous food sources. Although certain limitations were encountered, such as the specificity of the sampling depths for POM, and the small sample size of the representative species of the third trophic level, this study demonstrated the effectiveness of FAA as a powerful ecological tool for disentangling intricate lake food webs comprising various food sources. Overall, this study provided baseline information on basal food sources and trophic pathways of representative organisms from four tropical lakes. Taken together, FAA studies have wide application in understanding food webs, including anthropogenically-threatened lake ecosystems.

Abstract Agricultural practice has led to landscape simplification and biodiversity decline, yet recently, energy‐producing infrastructures, such as wind turbines, have been added to these simplified agroecosystems, turning them into multi‐functional energy‐agroecosystems. Here, we studied the trophic interactions of bats killed at wind turbines using a DNA metabarcoding approach to shed light on how turbine‐related bat fatalities may possibly affect local habitats. Specifically, we identified insect DNA in the stomachs of common noctule bats (Nyctalus noctula) killed by wind turbines in Germany to infer in which habitats these bats hunted. Common noctule bats consumed a wide variety of insects from different habitats, ranging from aquatic to terrestrial ecosystems (e.g., wetlands, farmland, forests, and grasslands). Agricultural and silvicultural pest insects made up about 20% of insect species consumed by the studied bats. Our study suggests that the potential damage of wind energy production goes beyond the loss of bats and the decline of bat populations. Bat fatalities at wind turbines may lead to the loss of trophic interactions and ecosystem services provided by bats, which may add to the functional simplification and impaired crop production, respectively, in multi‐functional ecosystems.