Search

Dietary metabarcoding has vastly improved our ability to analyse the diets of animals, but it is hampered by a plethora of technical limitations including potentially reduced data output due to the disproportionate amplification of the DNA of the focal predator, here termed "the predator problem". We review the various methods commonly used to overcome this problem, from deeper sequencing to exclusion of predator DNA during PCR, and how they may interfere with increasingly common multipredator‐taxon studies. We suggest that multiprimer approaches with an emphasis on achieving both depth and breadth of prey detections may overcome the issue to some extent, although multitaxon studies require further consideration, as highlighted by an empirical example. We also review several alternative methods for reducing the prevalence of predator DNA that are conceptually promising but require additional empirical examination. The predator problem is a key constraint on molecular dietary analyses but, through this synthesis, we hope to guide researchers in overcoming this in an effective and pragmatic way. [ABSTRACT FROM AUTHOR]

Objective: Understanding how energy moves through food webs and limits productivity at various trophic levels is a central question in aquatic ecology and can provide insight into drivers of fish population dynamics since many fish populations are food limited. In this study, we seek to better understand what factors drove a decline of >85% in the number of Rainbow TroutOncorhynchus mykiss found in the tailwater portion of the Colorado River below Glen Canyon Dam during 2012–2016. Methods: We estimate the production of dominant prey using data from previously published studies of Rainbow Trout abundance and growth alongside drift and diet samples. We test how prey production correlates to both proximate (e.g., nutrients) and distal (e.g., limnological conditions in the upriver reservoir) drivers. Result: Results suggest that gross consumption of invertebrate prey by the Rainbow Trout population declined from an annual mean of 423 to 69 kg/d. Daily production rates of dominant prey in aggregate declined from a high of 0.173 to 0.018 g·m−2·d−1. Chironomids accounted for 70% of the decline in prey production. Foraging efficiency by Rainbow Trout (range, 0.99–0.67) was high across the range of prey production rates. After the Rainbow Trout population had declined by ~90%, prey consumption saturated at higher rates of prey production and the gross quantity of daily drift exported from the reach increased from 8.9 to 12.7 kg/d. Conclusion: Rainbow Trout population dynamics are largely influenced by changes in prey production, which is itself driven by soluble reactive phosphorus (SRP) concentrations in the reservoir. The SRP model predicted that prey production would increase by 32 kg/d (SE, 9) for each 1 μg/L increase in SRP. These concentrations were indirectly influenced by reservoir hydrology and biogeochemistry, linkages that may extend far beyond the confines of this tailwater fishery and into the downstream reaches of the Grand Canyon's Colorado River ecosystem. Impact Statement: We combined Rainbow Trout diet, growth, and abundance estimates with concentrations of drifting invertebrates to estimate the biomass of Rainbow Trout prey produced over time. Trends in prey biomass production track trends in phosphorous concentrations in the river. [ABSTRACT FROM AUTHOR]

Due to their natural geochemistry, intertidal estuarine ecosystems are vulnerable to bioaccumulation of methylmercury (MeHg), a neurotoxin that readily bioaccumulates in organisms. Determining MeHg concentrations in intertidal invertebrates at the base of the food web is crucial in determining MeHg exposure in higher trophic level organisms like fish and birds. The processes that govern the production of MeHg in coastal ecosystems are influenced by many geochemical factors including sulfur species, organic matter, and salinity. The interactions of these factors with mercury are complex, and a wide variety of results have been reported in the literature. This paper reviews conceptual models to better clarify the various geochemical and physical factors that impact MeHg production and bioavailability in intertidal ecosystems. [ABSTRACT FROM AUTHOR]

Global warming is now predicted to exceed 1.5°C by 2033 and 2°C by the end of the 21st century. This level of warming and the associated environmental variability are already increasing pressure on natural and human systems. Here we emphasize the role of physiology in the light of the latest assessment of climate warming by the Intergovernmental Panel on Climate Change. We describe how physiology can contribute to contemporary conservation programmes. We focus on thermal responses of animals, but we acknowledge that the impacts of climate change are much broader phylogenetically and environmentally. A physiological contribution would encompass environmental monitoring, coupled with measuring individual sensitivities to temperature change and upscaling these to ecosystem level. The latest version of the widely accepted Conservation Standards designed by the Conservation Measures Partnership includes several explicit climate change considerations. We argue that physiology has a unique role to play in addressing these considerations. Moreover, physiology can be incorporated by institutions and organizations that range from international bodies to national governments and to local communities, and in doing so, it brings a mechanistic approach to conservation and the management of biological resources. [ABSTRACT FROM AUTHOR]

Freshwater ecosystems are subjected to a broad range of anthropogenic threats. Understanding the responses of aquatic biota to these threats and identifying potential mitigating actions presents a major challenge for ecologists and natural resource managers. Here, we investigated the responses of fish communities to land use change at different scales.We assessed patterns of food web structure of fish across a gradient of human impacts in the Atlantic Forest ecoregion of southeast Brazil. We analysed stomach contents of fish and evaluated the response of five food web metrics to variation in land use change. We also calculated four metrics for intra‐guild comparisons in the omnivore, insectivore, and algivore–insectivore guilds.The proportional abundance of omnivores increased as temperature increased and canopy cover decreased. Food web specialisation decreased in deforested streams with higher nutrient input, suggesting higher resource sharing by those fish communities. Fish in the algivore–insectivore guild consumed fewer types of macroinvertebrates in streams with low canopy cover. The opposite pattern was observed within the insectivore guild with individuals consuming a larger variety of prey in impacted streams.Deforestation, and increases in water temperature and nutrient input, influenced inter‐species and intra‐guild trophic interactions in fish communities in these Atlantic Forest streams, even though the richness of fish community and composition of intra‐guild species remained unchanged. Some food web metrics were sensitive to the direct and indirect effects of disturbance on these fish communities.Our study has shown that assessments of trophic interactions can detect the effects of land‐use disturbance on fish communities that may not be evident from simple measures of species richness and composition. This approach provides direct insights into the functional integrity of fish communities and should be considered for monitoring the success of programmes aimed to protect and, where necessary, restore freshwater ecosystems. [ABSTRACT FROM AUTHOR]

Qilianyu Islands coral reefs (QICR), located in the northeastern part of the South China Sea, has been affected by human activities and natural disturbance. To characterize the trophic structure, ecosystem properties and keystone species of this region, a food-web model for the QICR is developed using methods involving a mass-balance approach with Ecopath with Ecosim software. Trophic levels range from 1.00 for detritus and primary producers to 3.80 for chondrichthyes. The mean trophic transfer efficiency for the entire ecosystem is 13.15%, with 55% of total energy flow originating from primary producers. A mixed trophic impact analysis indicates that coral strongly impacts most components of this ecosystem. A comparison of our QICR model with that for other coral reef ecosystems suggests that the QICR ecosystem is immature and/or is degraded. [ABSTRACT FROM AUTHOR]

BACKGROUND: Understanding the networks of trophic interactions into which generalist predators are embedded is key to assessing their ecological role of in trophic networks and the biological control services they provide. The advent of affordable DNA metabarcoding approaches greatly facilitates quantitative understanding of trophic networks and their response to environmental drivers. Here, we examine how key environmental gradients interact to shape predation by Lycosidae in highly dynamic vegetable growing systems in China. RESULTS: For the sampled Lycosidae, crop identity, pesticide use and seasons shape the abundance of prey detected in spider guts. For the taxonomic richness of prey, local‐ and landscape‐scale factors gradients were more influential. Multivariate ordinations confirm that these crop‐abundant spiders dynamically adjust their diet to reflect environmental constraints and seasonal availability to prey. CONCLUSION: Plasticity in diet composition is likely to account for the persistence of spiders in relatively ephemeral brassica crops. Our findings provide further insights into the optimization of habitat management for predator‐based biological control practices. © 2022 Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

The accelerating exhaustion of non-renewable natural resources and the urgent need for sustainable practices have prompted the exploration of alternative methodologies in production processes. Food webs illustrate the predator-prey relationships between species in natural ecosystems, and their properties can offer valuable insights for improving economic and industrial systems, potentially leading to reduced emissions, costs, and improved process efficiency. While some food web metrics have been used for various purposes like establishing industry-nature analogies, comparing industrial networks to natural ecosystems, and configuring industrial networks, investigation of the role of the connectance metric in designing industrial networks, particularly in optimizing theoretical EIPs, is still scarce. This study investigates the role of connectance in optimizing industrial networks within eco-industrial parks, specifically focusing on the construction sector. A scenario analysis for seven conceptual eco-industrial parks serves as an illustration of how this approach can be used. The food web metric values of these eco-industrial parks are compared among themselves and against biological averages. The results reveal that maximizing connectance in eco-industrial parks is not an effective strategy for network optimization, as indicated by previous literature which points to potential instability. Instead, configurations that closely resemble natural food web metrics may provide better sustainability and efficiency if the limitations of the study are addressed, and the validity of this assumption is confirmed through quantitative tests. This study contributes theoretically by developing a guide for designing eco-industrial parks and introduces two key methodologies: based on particular criteria, a method for identifying and selecting potential future industrial symbiosis implementations targeted a sector and an innovative approach for sector-specific park design based on natural objectives and constraints, serving as a valuable decision-making tool for practitioners and policymakers. [Display omitted] • Nature is used as a guide to design symbiotic industrial networks. • A methodology inspired by biological principles is developed. • Seven theoretical symbiotic industrial networks scenarios are developed. • Connectance's role in optimizing eco-industrial parks is explored. • Targeting maximum connectance is not ideal for industrial network optimization. [ABSTRACT FROM AUTHOR]

• 3 lakes across latitudinal gradient in Europe (Croatia, Poland, Lithuania) were sampled. • Stable isotopes of carbon and nitrogen were measured in tissues of planktonic crustaceans. • Strong partitioning of isotopic niches among planktonic crustaceans was found. • C:N ratio (proxy for lipid content) declined with trophic level. We examined the feeding ecology of planktonic crustaceans at three waterbodies situated across a latitudinal gradient in Europe (Croatia, Poland, Lithuania) using stable isotope measurements (δ13C, δ15N) in animal tissues. Relative, lake-specific values of δ15N showed that in all lakes, calanoid copepods occupied the highest trophic position, while Daphnia sp. and Diaphanosoma sp. were located closer to primary producers with Cyclopoid copepods located between these groups. We found a negative correlation between C:N ratio (proxy for lipid content) and δ15N, which indicates lipid content declined with the trophic level of the animals. Employment of stable isotope-based approach allows better recognition of trophic linkages than could be inferred from classical methods, and therefore our results contribute improvement of management strategies developed for aquatic ecosystems. [ABSTRACT FROM AUTHOR]

Bromalites are important indicators of dietary habits and potential predator-prey relationships, therefore, they largely enhance our comprehension of trophic interactions within marine ecosystems. A multi-disciplinary investigation was conducted on conodont-bearing bromalites discovered from the 'fish-bearing nodule layers' of the uppermost Lower Qinglong Formation (Longtan section, Nanjing, South China) that typifies one of the peri-Pangean distributed 'Triassic early Fish Faunas' (TEFF). The conodont species Scythogondolella milleri within some bromalites, visualized using X-ray microtomography, pinpoints the latest Smithian (Olenekian, Early Triassic) in age. These bromalites are described and classified into six distinct morphotypes: M1 (slender), M2 (raindrop-like), M3 (tadpole-like), M4 (kidney-like), M5 (folded), and M6 (plate-like). Morphological, inclusion-based, and geochemical analyses allow us to identify three morphotypes as coprolites with carbonaceous or phosphatic matrices. Conversely, the other three morphotypes, characterized by a scarcity of matrix material, are inferred to be regurgitalites. They were inferred to be likely produced by ammonoids, thylacocephalans, actinopterygians, and coelacanths. Subsequently, a trophically multileveled (at least 5 levels) end-Smithian marine ecosystem is reconstructed, in which multiple predators within higher trophic levels, including predatory invertebrates (e.g., ammonoids, crustaceans) and predatory fishes of different taxa, have heavy predation on conodonts. Under these conditions, conodonts, who are ecologically diverse, small-sized macrophagous predators or scavengers with a benthic or pelagic lifestyle, are posited to be an important food source for higher trophic level predators in this ecosystem. Furthermore, multiple predators of higher trophic levels preying on conodonts, alongside the consensus that conodonts have suffered modest losses during the end-Permian mass extinction (EPME) and dramatically re-diversified thereafter, implies that conodonts had most likely served as a key trophic linkage between pelagic and benthic food webs in the Early Triassic marine ecosystem, which was dominated by nektons, particularly fishes. • Conodont-bearing bromalites are yielded from a 'Triassic early Fish Fauna'. • Bromalites provide behavioural data including predation, scavenging, and vomiting. • Multiple nektons heavily prey on conodonts in an end-Smithian community. • Conodonts link pelagic and benthic food webs in the Early Triassic oceans. [ABSTRACT FROM AUTHOR]

Along the northern Mid-Atlantic Ridge (nMAR), in habitats under moderate (<10 °C) hydrothermal influence on the Snake Pit vent field (SP), large assemblages dominated by Bathymodiolin mussels remain poorly characterised, contrary to those in warmer habitats dominated by gastropods and alvinocaridid shrimps that were recently described. In this study, we assessed and compared the population structure, biomass, diversity and trophic interactions of two Bathymodiolus puteoserpentis assemblages and their associated fauna at SP. Three sampling units distanced by 30 cm were sampled in 2014 during the BICOSE cruise at the top of the Moose site (''Elan'' site), while few meters further down three others, distanced by ∼1 m were obtained in 2018 during the BICOSE 2 cruise at the edifice's base. We observed a micro-scale heterogeneity between these six sampling units partially explained by temperature variations, proximity to hydrothermal fluids and position on the edifice. Meiofauna dominate or co-dominate most of the sampling units, with higher densities at the base of the edifice. In terms of macrofauna, high abundance of Pseudorimula midatlantica gastropods was observed at the top of the vent edifice, while numerous Ophioctenella acies ophiuroids were found at the base. Contrary to what was expected, the apparent health and abundance of mussels seems to indicate a current climax stage of the community. However, the modification of B. puteoserpentis isotopic signatures, low number of juveniles decreasing over the two years and observations made during several French cruises in the study area raise questions about the fate of the B. puteoserpentis population over time, which remains to be verified in a future sampling campaign. • Assemblage heterogeneity at different scales linked to fluid proximity & location. • Meiofaunal groups dominated. Macrofaunal disparity between top and base of edifice. • Low number of mussel juveniles over time questions the future of the population. [ABSTRACT FROM AUTHOR]

A better understanding of trophic interactions between hardhead catfish (Ariopsis felis) and gafftopsail catfish (Bagre marinus) is crucial for developing multi-species management strategies for the northern Gulf of Mexico (GOM). These two species are often aggregated in food web models; however, limited data are available to substantiate this approach. Therefore, the present study aimed to describe the dietary habits of hardhead catfish and gafftopsail catfish using analysis of stomach contents aided by DNA barcoding. Hardhead (n = 693) and gafftopsail (n = 655) catfish were sampled in the northern GOM from 2015–2019 using both fisheries-dependent and -independent techniques. The average percent number (%N), average percent mass (%M), prey specific number (%PN), prey specific mass (%PM), and prey-specific index of relative importance (%PSIRI) were computed to quantify prey species. The stomach content analysis identified distinct differences in diet between hardhead and gafftopsail catfish. Crustaceans were the most important prey for hardhead catfish, while gafftopsail catfish showed a significantly broader dietary breadth and were primarily piscivorous. Multivariate analyses indicated that the location of capture explained the greatest amount of diet variability for both species. These findings address fundamental knowledge gaps regarding the dietary habits of hardhead and gafftopsail catfish in northern GOM ecosystems.

In 2011, a first comprehensive assessment of the footprints of climate change on Arctic marine ecosystems (such as altered distribution ranges, abundances, growth and body conditions, behaviours and phenologies, as well as community and regime shifts) was published. Here, we re-assess the climate-driven impacts reported since then, to elucidate to which extent and how observed ecological footprints have changed in the following decade (2011 to 2021). In total, 98 footprints have been described and analysed. Most of those impacts reported in the 2011 assessment are reconfirmed and can, hence, be assumed as continuing trends. In addition, novel footprints (behavioural changes, diet changes, altered competition and pathogen load) are described. As in 2011, most reported footprints are related to changes in distribution ranges, abundances, biomass and production. Range shifts have mostly been observed for fish species, while behavioural changes have mainly been reported for mammals. Primary production has been observed to further increase in Arctic seas. The footprints on pelagic herbivores, particularly the key species Calanus spp., are less clear. In comparison to 2011, more complex, cascading effects of climate change, such as increased bowhead whale body conditions due to increased primary production, have been reported. The observed footprints, and the trends that they indicate, strongly suggest that due to further northward range shifts of sub-Arctic and boreal species Arctic seas are likely to experience increasing species richness in the future. However, a tipping point may be reached, characterized by subsequent biodiversity decline, when Arctic-endemic species will go extinct as ocean warming and/or acidification will exceed their physiological adaptation capacity. Furthermore, as invading boreal species have a competitive advantage due to their wider physiological and trophic range, Arctic species abundances are predicted to decrease. Overall, the future Arctic Ocean will very likely experience increasing numbers and intensities of climate-change footprints.

Although the concept of trophic interactions has been used for a long time, there are still considerable gaps in our understanding of the effect of various environmental factors on trophic interactions within river fish assemblages. Carbon (δ13C) and nitrogen (δ15N) stable isotope ratios of 20 species of fish belonging to both eurytopic and rheophilic ecological groups from a large temperate rivers were used to evaluate overall trophic niche use and trophic position of species, and to find out how environmental variability associated with nutrient loading affects individual and community-wide aspects of trophic structure. The study was carried out at 11 sites along the European rivers Vltava and Elbe, representing a continuous gradient of pollution and habitat degradation. Corrected Standard Ellipse Area (SEAc) was significantly larger for the group of eurytopic ecological species than for rheophilic species. Despite narrower isotopic niche space, rheophilic fish species occupied a higher trophic position, suggesting that these species use resources more enriched in 15N. Of the 11 environmental variables tested, nutrients had a significant effect on trophic niche area of species (SEAc), indicating that eutrophication is of critical importance for fish assemblages. Isotopic niche area of species was found to be positively influenced by total phosphorus, and negatively affected by concentrations of nitrate (N-NO3−) and ammonia (N-NH4+). A negative association between oxygen demand and a measure of trophic diversity - mean distance to centroid (CD)- and a measure of density and clustering of species - mean nearest neighbor distance (MNND)- were found, indicating that the oxygen demand is a key factor influencing community trophic structure. An observed pattern where nutrient loading influenced both individual species and trophic structure of the fish assemblage provides strong support for an anthropogenic influence on riverine food webs.

Species invasions can lead to ecological regime shifts by altering food web structure and changing nutrient cycling. Stable isotopes are a powerful tool to understand the potential and realized impacts of invasive species on food webs, especially when used in tandem with other dietary tracers. An invasion by one of the most notorious freshwater invaders in North America, the quagga mussel (Dreissena bugensis), is imminent in Lake Champlain, United States. An invasion by this filter feeder has the potential to drastically alter energy pathways and destabilize pelagic fisheries via bottom-up impacts. However, the extent and magnitude of these impacts depend on the current food web structure of the mid-trophic pelagic food web, which was previously not well described. We used Bayesian stable isotope mixing models informed by stomach content analysis to identify which energy pathways are currently most important to mid-trophic level fishes. We determined that in the Main Lake basin, the spring phytoplankton bloom and deep chlorophyll layer – the resources most vulnerable to quagga mussels – provide a disproportionate amount of support to the pelagic food web via zooplankton and the migrating macroinvertebrate Mysis. The food web in the Northeast Arm of Lake Champlain is supported by epilimnetic phytoplankton, which is more protected from the filtration effects of quagga mussels than the deep chlorophyll layer. However, the Northeast Arm will likely not provide a high-quality foraging refuge to coldwater pelagic fish due to unfavorable oxythermal conditions. The mid-trophic food web of Lake Champlain—and consequently piscivores who rely on these prey—may be vulnerable to the impending quagga mussel invasion if migratory Mysis are not able to shift their diet to benthic resources.

The extent of direct interactions between large mammalian herbivores (LMH) and plant-dwelling arthropods (PDA), i.e., the ingestion of PDA by LMH, remains largely unexplored. Grazing LMH may ingest a variety of PDA, yet, it is unknown how different foraging strategies (i.e., browsing, grazing, etc.) influence the ingestion of PDA or whether individual variation within herds affects it. Here we examine how individual variation within a herd of browsing LMH impacts PDA ingestion. This was done using a DNA metabarcoding analysis on feces collected monthly from marked individuals within a herd of free-ranging goats. We found that goats frequently ingest PDA while feeding (all samples contains PDA), including a complex food-chain of herbivores, predators and parasites, which differed over the season and among individual goats. In total, 63 families of insects and 9 families of arachnids from 15 orders were ingested by the goats. Most ingested PDA were herbivores with reduced mobility, such as immature or sessile species. Highly mobile and noxious PDA were rarely detected. We show for the first time that ingestion of PDA by LMH is influenced by seasonal and individual variation within the herd and that it is common among LMH, regardless of feeding strategy or habitat.

Predation can play an important role in population, community and ecosystem processes. When predator guilds are diverse, fluctuations in individual predator populations may have small influences on the guild at large, suggesting that predator diversity stabilizes the amount of predation prey experience. The strength of this phenomenon depends on how synchronously populations within predator assemblages vary and whether all predators are equally important consumers. We utilized a database of biomasses of fish species across ten temperate marine ecosystems paired with diet composition and feeding rate information from mass-balance food web models to develop a predation index that weights the importance of predators on a prey based on predator feeding habits. Using the index, we asked how diverse sources of predation in these ecosystems are and how much diversity stabilizes variability in predation. Predator assemblages displayed a wide range of diversity; in one-third of assemblages, a single predator group accounted for over half of all predation. Abundances of predator populations within assemblages generally varied independently of one another (neither synchronously nor asynchronously), implying an intermediate stabilization on predation intensity by predator diversity. Accounting for interaction strength (versus mere presence) is critical for interpreting the predator landscape; doing so led to a wider range in predator assemblage diversity and less synchronous assemblages. This work challenges conventional notions that marine food webs are diverse and therefore less susceptible to predator control. Future work should consider the temporal variability of the predator assemblages and account for differences in mortality induced by each predator population.

The daunting complexity of ecosystems has led ecologists to use mathematical modelling to gain understanding of ecological relationships, processes and dynamics. In pursuit of mathematical tractability, these models use simplified descriptions of key patterns, processes and relationships observed in nature. In contrast, ecological data are often complex, scale-dependent, space-time correlated, and governed by nonlinear relations between organisms and their environment. This disparity in complexity between ecosystem models and data has created a large gap in ecology between model and data-driven approaches. Here, we explore data assimilation (DA) with the Ensemble Kalman filter to fuse a two-predator-two-prey model with abundance data from a 2600+ day experiment of a plankton community. We analyse how frequently we must assimilate measured abundances to predict accurately population dynamics, and benchmark our population model's forecast horizon against a simple null model. Results demonstrate that DA enhances the predictability and forecast horizon of complex community dynamics.

Freshwater systems are experiencing rapid biodiversity losses resulting from high rates of habitat degradation. Ecological condition is typically determined through identifying either macroinvertebrate or diatom bioindicator assemblages and comparing them to their known tolerance to stressors. These comparisons are typically conducted at family or genus levels depending on the availability of taxonomic keys and expertise for focal groups. The objective of this study was to test whether a more taxonomically comprehensive assessment of communities in benthic samples can provide a different perspective of ecological conditions. DNA metabarcoding was used to identify macroinvertebrates and diatoms from kick-net samples collected from sites with different habitat status. Sites with ‘good’ condition were associated with higher beta diversity as well as slightly higher directed connectance and modularity indicating higher resilience compared with ‘fair’ condition sites. Indicator value and correlation analyses used DNA metabarcoding data to detect 29 site condition indicator species consistent with known bioindicators and expected relative tolerances. DNA metabarcoding and trophic network analysis also recovered 11 keystone taxa. This study demonstrates the importance of taxonomic breadth across trophic levels for generating biotic data to study ecosystem status, with the potential to scale-up ecological assessments of freshwater condition, trophic stability, and resilience.

Aim: Our goal was to quantify nitrogen flows and stocks in green–brown food webs in different ecosystems, how they differ across ecosystems and how they respond to nutrient enrichment. Location: Global. Time period: Contemporary. Major taxa studied: Plants, phytoplankton, macroalgae, invertebrates, vertebrates and zooplankton. Methods: Data from >500 studies were combined to estimate nitrogen stocks and fluxes in green–brown food webs in forests, grasslands, brackish environments, seagrass meadows, lakes and oceans. We compared the stocks, fluxes and metabolic rates of different functional groups within each food web. We also used these estimates to build a dynamical model to test the response of the ecosystems to nutrient enrichment. Results: We found surprising symmetries between the green and brown channels across ecosystems, in their stocks, fluxes and consumption coefficients and mortality rates. We also found that nitrogen enrichment, either organic or inorganic, can disrupt this balance between the green and brown channels. Main conclusions: Linking green and brown food webs reveals a previously hidden symmetry between herbivory and detritivory, which appears to be a widespread property of natural ecosystems but can be disrupted by anthropogenic nitrogen additions. [ABSTRACT FROM AUTHOR]

The trophic interactions between consumers and resources play a vital role in the stability of communities. In river systems, fragmentation of natural habitats and environmental changes alters the energy basis and community composition, consequently leading to variations in the community's trophic structure and niche space. However, our understanding of how the trophic structure responds to environmental changes is still very limited. Here, based on stable isotope data, we explored and compared trophic positions (TPs), community‐wide trophic metrics, and isotope niche space of fish communities in three reaches with different hydrogeomorphic conditions along a highly regulated subtropical river over three seasons. The community trophic structure and niche space showed notable spatiotemporal variations. Overall, the downstream reach had lower TPs, trophic diversity but higher trophic redundancy. The middle reach occupied a wider isotope niche space than other reaches, with the largest niche size during autumn. Furthermore, the niche overlap was relatively high in winter between reaches and in the downstream between seasons. The results implied a homogenization of feeding functional groups and energy flow pathways of species in the downstream community associated with the change of energy source and stability of hydrological conditions. The relationship between trophic structure and environmental factors suggested that the dam‐induced alteration in hydrological‐related aspects may drive the changes in the functional group composition, together with changes in energy basis, resulting in differences in the trophic structure of the community. The results of the present study deepen our understanding of how ecosystem functions respond to disturbance, thus contributing to improved ability to conserve river ecosystems. [ABSTRACT FROM AUTHOR]

To investigate the potential long-term consequences of environmental warming in subtropical systems, we compare the trophic structure of shallow lakes in tropical and subtropical regions. In total, 25 meso-eutrophic lakes with piscivorous fish were sampled during summer along a latitudinal gradient in South America. The fish catch per unit of effort and the omnivorous fish to zooplankton biomass ratios were significantly lower in the tropical lakes. Despite the lower fish biomass, no significant difference was found in zooplankton or phytoplankton communities or in the zooplankton to phytoplankton biomass ratio between the two sets of lakes. Nevertheless, regression models based on the combined dataset show higher cyanobacteria and total phytoplankton biomass at lower zooplankton to phytoplankton biomass ratio and higher omnivorous fish to zooplankton biomass ratio. Cyanobacteria biomass was dominated by non bloom-forming taxa and was inversely related to the biomass of calanoid copepods suggesting that these herbivores may play an important role in controlling edible cyanobacteria in warm shallow lakes. Overall, our results, however, suggest that warming will have relatively minor impacts on the pelagic trophic structure of shallow subtropical lakes supporting the idea of weaker trophic cascades in warm (sub)tropical lakes in comparison to temperate ones. [ABSTRACT FROM AUTHOR]

Species interactions shape the diversity and resilience of ecological networks. Plant and animal traits, as well as phylogeny, affect interaction likelihood, driving variation in network structure and tolerance to disturbance.We investigated how traits and phylogenetic effects influenced network‐wide interaction probabilities and examined the consequences of extinction on the structure and robustness of ecological networks.We combined both mutualistic and antagonistic interactions of animals (55 species, Infraorder Lemuriformes, Order Primates) and their food plants (590 genera) throughout Madagascar to generate ecological networks. We tested the effects of both lemur and plant traits, biogeographic factors and phylogenetic relatedness on interaction probability in these networks using exponential random graph models. Next, we simulated animal and plant extinction to analyse the effects of extinction on network structure (connectance, nestedness and modularity) and robustness for mutualistic, antagonistic and combined plant–animal networks.Both animal and plant traits affected their interaction probabilities. Large, frugivorous lemurs with a short gestation length, occurring in arid habitats, and with a Least Concern threat level had a high interaction probability in the network, given all other variables. Closely related plants were more likely to interact with the same lemur species than distantly related plants, but closely related lemurs were not more likely to interact with the same plant genus. Simulated lemur extinction tended to increase connectance and modularity, but decrease nestedness and robustness, compared to pre‐extinction networks. Networks were more tolerant to plant than lemur extinctions.Lemur–plant interactions were highly trait structured and the loss of both lemurs and plants threatened the tolerance of mutualistic, antagonistic and combined networks to future disturbance. [ABSTRACT FROM AUTHOR]

Facultative scavenging by predatory carnivores is a prevalent but frequently underestimated feeding strategy. DNA‐based methods for diet analysis, however, do not allow to distinguish between scavenging and predation, thus, the significance of scavenging on population dynamics and resource partitioning is widely unknown. Here, we present a methodological innovation to differentiate between scavenging and fresh prey consumption using prey RNA as a target molecule. We hypothesized that the rapid post‐mortem breakdown of RNA in prey tissue should lead to a significantly lower detection probability of prey RNA than DNA when carrion rather than fresh prey is consumed. To test this hypothesis, ground beetles (Pseudoophonus rufipes [De Geer]) were offered either fresh or 1‐day‐old dead Drosophila melanogaster fruit flies (carrion). The detectability of prey RNA and DNA in the beetles' regurgitates was assessed with diagnostic Drosophila‐specific RT‐PCR and PCR assays at 0, 6, 12, 24 and 48 h post‐feeding. After fresh fly consumption, prey RNA and DNA were detectable equally well at all times. When carrion prey was consumed, the detection strength of prey RNA immediately after feeding was significantly lower than that of prey DNA and reached zero in most samples within 6 h of digestion. Our findings provide evidence that prey RNA allows distinguishing between the consumption of fresh and scavenged prey, thereby overcoming a long‐known weakness of molecular diet analysis. The assessment of prey RNA offers a generally applicable approach for examining the importance of scavenging in food webs to unravel its functional consequences for populations, communities, and ecosystems. [ABSTRACT FROM AUTHOR]

Microplastics (MPs) contamination in marine environments is of increasing concern, as plastic particles are globally ubiquitous across ecosystems. A large variety of aquatic taxa ingest MPs, but the extent to which animals accumulate and transfer MPs through food webs is largely unknown. In this study, we quantified MP uptake in bivalves, crabs, echinoderms, and fish feeding at different trophic levels at three sites on southern Vancouver Island. We paired stable‐isotope food web analysis with MP concentrations in digestive tracts across all trophic levels and in fish livers. We then used Bayesian generalized linear mixed models to explore whether bioaccumulation and biomagnification were occurring. Our results showed that MPs (100–5000 μm along their longest dimension) are not biomagnifying in marine coastal food webs, with no correlation between the digestive tract or fish liver MP concentrations and trophic position of the various species. Ecological traits did, however, affect microplastic accumulation in digestive tracts, with suspension feeder and smaller‐bodied planktivorous fish ingesting more MPs by body weight. Trophic transfer occurred between prey and predator for rockfish, but higher concentrations in full stomachs compared with empty ones suggested rapid excretion of ingested MPs. Collectively, our findings suggested the movement of MP through marine food webs is facilitated by species‐specific mechanisms, with contamination susceptibility a function of species biology, not trophic position. Furthermore, the statistical methods we employ, including machine learning for classifying unknown particles and a probabilistic way to account for background contamination, are universally applicable to the study of microplastics. Our findings advance understanding of how MPs enter and move through aquatic food webs, suggesting that lower‐trophic‐level animals are more at risk of ingesting >100‐μm MPs, relative to higher‐trophic‐level animals. Our work also highlights the need to advance the study of <100‐μm MPs, which are still poorly understood and may need to be considered separately in ecological risk assessments. [ABSTRACT FROM AUTHOR]

Copyright of Ecoscience (Ecoscience) is the property of Taylor & Francis Ltd and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Climate change and anthropogenic activities are producing a range of new selection pressures, both abiotic and biotic, on marine organisms. Although it is known that climate change can differentially affect fitness‐related traits at different trophic levels of the food web, it is not clear if different trophic levels will respond via phenotypic plasticity in the form of maintenance of phenotypes in the face of abiotic and biotic environmental stress similarly. To answer this question, we combined a mesocosm experiment (120 days) using a food web comprising three gastropod species from two trophic levels (grazers and meso‐predators) and a meta‐analysis including 38 studies to address whether different trophic levels exhibit similar phenotypic responses to abiotic and biotic variables. Abiotic (ocean acidification) and biotic (predation) stress significantly influenced body mass, shell mass, shell thickness and shell strength in both grazers and meso‐predators in the mesocosm experiment, with the magnitude of OA effects greater on the meso‐predator than the grazers; a result supported by the meta‐analysis. In contrast, both mesocosm experiment and meta‐analysis found that predation risk induced stronger responses in shell morphology for grazers compared to meso‐predators. Together, our findings indicate that higher trophic level species are better able to maintain aspects of their phenotype under OA, suggesting that they may show greater tolerance to climate change effects in general, while lower trophic levels express higher levels of plastic inducible defences to maintain function when under threat of predation. By using marine snails as a model, our study provides new knowledge for understanding how changing environmental conditions may alter biological interactions, and increases our understanding of how climate change may affect ecological communities in which gastropods play a key role. [ABSTRACT FROM AUTHOR]

Around 36,000 km3 of freshwater flows through rivers and estuarine ecosystems and enter the world's coastal fishing regions every year. The flow of freshwater and sediments creates regional changes in coastal circulation, stimulates marine productivity and helps define the hydrologic properties of estuarine and oceanic waters. These processes can affect different life stages of marine species either directly, through variations in salinity and temperature, or indirectly, due to changes in the availability of food and habitat. This paper reviews the relationship between freshwater flowing through estuarine and coastal ecosystems, and the variable productivity associated with global marine capture fisheries. The results of a global synthesis revealed that 72% of species representing 77% of the total catch (43 million tonnes) were linked to river flows for at least some part of their life cycle. Insights into how the relationship between flow and fishery production varies globally indicates wild capture fisheries and freshwater resources would benefit from an integrated planning and management approach. [ABSTRACT FROM AUTHOR]

The potential for forecasting the dynamics of ecological systems is currently unclear, with contrasting opinions regarding its feasibility due to ecological complexity. To investigate forecast skill within and across systems, we monitored a microbial system exposed to either constant or fluctuating temperatures in a 5‐month‐long laboratory experiment. We tested how forecasting of species abundances depends on the number and strength of interactions and on model size (number of predictors). We also tested how greater system complexity (i.e. the fluctuating temperatures) impacted these relations. We found that the more interactions a species had, the weaker these interactions were and the better its abundance was predicted. Forecast skill increased with model size. Greater system complexity decreased forecast skill for three out of eight species. These insights into how abundance prediction depends on the connectedness of the species within the system and on overall system complexity could improve species forecasting and monitoring. [ABSTRACT FROM AUTHOR]

Plankton ecologists ultimately focus on forecasting, both applied and environmental outcomes. We review how appreciating planktonic ciliates has become central to these predictions. We explore the 350‐year‐old canon on planktonic ciliates and examine its steady progression, which has been punctuated by conceptual insights and technological breakthroughs. By reflecting on this process, we offer suggestions as to where future leaps are needed, with an emphasis on predicting outcomes of global warming. We conclude that in terms of climate change research: (i) climatic hotspots (e.g. polar oceans) require attention; (ii) simply adding ciliate measurements to zooplankton/phytoplankton‐based sampling programs is inappropriate; (iii) elucidating the rare biosphere's functional ecology requires culture‐independent genetic methods; (iv) evaluating genetic adaptation (microevolution) and population composition shifts is required; (v) contrasting marine and freshwaters needs attention; (vi) mixotrophy needs attention; (vii) laboratory and field studies must couple automated measurements and molecular assessment of functional gene expression; (viii) ciliate trophic diversity requires appreciation; and (ix) marrying gene expression and function, coupled with climate change scenarios is needed. In short, continued academic efforts and financial support are essential to achieve the above; these will lead to understanding how ciliates will respond to climate change, providing tools for forecasting. [ABSTRACT FROM AUTHOR]

The growth of any organism depends on habitat conditions, food availability, and their seasonal interactions. Yet in the vast literature on Pacific salmon (Oncorhynchus), the seasonal interaction between habitat conditions and food availability has received relatively little attention. We examined juvenile Oncorhynchus mykiss rearing, physical habitat, and resource phenologies in two Mediterranean coastal streams—one perennial, cool, and shaded and the other intermittent, seasonally warm, and sunny. We used a bioenergetic model to investigate the timing and magnitude of growth potential for drift‐foraging O. mykiss during the spring and summer in both systems. Growth potential peaked at least 2 months earlier in the intermittent stream than in the perennial stream. By early summer (June), growth potential had declined in the intermittent stream, whereas growth rates were peaking in the perennial stream. However, the mid‐July lipid content of juvenile O. mykiss in the intermittent stream was nearly twice that of fish in the perennial stream. By late summer (August), foraging profitability declined in both streams, as abiotic conditions in the intermittent stream approached lethal. In contrast, the perennial stream maintained suitable abiotic conditions even though the growth rate was low. We suggest that the divergent resource phenologies and seasonal mortality risks experienced by anadromous O. mykiss rearing in these streams could drive diversification of traits governing size, age, and timing of outmigration. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Hydrobiology is the property of Editorial Department of Journal of Hydrobiology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Limited data are available about the coastal ecology of the Calabria region, in the southern Italy. As well, data about the levels of biodiversity and the structure of food webs in these environments are totally missing. However, considering the wide range of physical and ecological conditions distinguishing these ecosystems, a remarkable spread of biodiversity is expected. This review represents a first attempt to describe and estimate the structure of the food webs in a range of shallow stations along the south-western coasts of southern Italy, in the Ionian Sea. They comprise a Special Area of Conservation (Amendolara shoal), an urbanized area (Sibari), a sandy area impacted by industrial installations (Corigliano) and a seagrass meadow (Calopezzati). For each of these stations, we produced ecological simulation models based on the available information in order to estimate the structure of food webs. In particular, the patterns of distribution of trophic resources resulting from literature data were statistically compared to a theoretical model based on the physical and ecological features of coastal ecosystems. The model was responsive and predicted remarkable differences in the compartmentalization of trophic resources among stations, due to the diversity of substrates and the anthropic activities impacting each area. Large availability of resources for omnivores and detritivores characterized most stations. A noteworthy richness of trophic resources for herbivores was forecasted off Amendolara and Calopezzati. In parallel, the model obtained for the urbanized area of Sibari predicted a higher abundance of trophic resources for filter feeders, especially in the deepest station., (Copyright © 2024. Published by Elsevier B.V.)

Food webs are typically defined as being macro-organism-based (e.g., plants, mammals, birds) or microbial (e.g., bacteria, fungi, viruses). However, these characterizations have limits. We propose a multilayered food web conceptual model where microbial food webs are nested within food webs composed of macro-organisms. Nesting occurs through host-microbe interactions, which influence the health and behavior of host macro-organisms, such that host microbiomes likely alter population dynamics of interacting macro-organisms and vice versa. Here, we explore the theoretical underpinnings of multilayered food webs and the implications of this new conceptual model on food web ecology. Our framework opens avenues for new empirical investigations into complex ecological networks and provides a new lens through which to view a network's response to ecosystem changes., Competing Interests: Declaration of interests The authors have no interests to declare., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

The composition of fatty acids in the muscle tissue of the unique Central Asian carp-like fish, Potanin Altai osman Oreoleuciscus potanini, was studied for the first time. The populations of these fish in the reservoirs of the semiarid zone (Durgun and Taishir) during the period of their formation are considered. It was shown that the content of eicosapentaenoic (EPA) and docosahexaenoic (DHA) acids in O. potanini corresponds to the median of this value in the order Cypriniformes. It was established that the basis of the food web of the herbivorous form of this species consists of microalgae (diatoms, Euglena and, possibly, chrysophytes), as well as bacteria. At the same time, the levels of bacterial biomarkers, 15-17BCFA and 17:0 were significantly higher in fish in the Durgun reservoir, whereas the level of EPA (diatom biomarker) in O. potanini was higher in the Taishir reservoir. The established higher values of the heavy nitrogen isotope content in the muscles of O. potanini from the Taishir reservoir are most likely associated with the yet unformed benthic communities and with the incomplete diversification of the riverine form of the Potanin Altai osman into lacustrine forms., (© 2024. Pleiades Publishing, Ltd.)

The increase in plastic debris and its environmental impact has been a major concern for scientists. Physical destruction, chemical reactions, and microbial activity can degrade plastic waste into particles smaller than 5 mm, known as microplastics (MPs). MPs may eventually enter aquatic ecosystems through surface runoff. The accumulation of MPs in aquatic environments poses a potential threat to finfish, shellfish, and the ecological balance. This study investigated the effect of MP exposure on freshwater and marine fish. MPs could cause significant harm to fish, including physical damage, death, inflammation, oxidative stress, disruption of cell signalling and cellular biochemical processes, immune system suppression, genetic damage, and reduction in fish growth and reproduction rates. The activation of the detoxification system of fish exposed to MPs may be associated with the toxicity of MPs and chemical additives to plastic polymers. Furthermore, MPs can enhance the bioavailability of other xenobiotics, allowing these harmful substances to more easily enter and accumulate in fish. Accumulation of MPs and associated chemicals in fish can have adverse effects on the fish and humans who consume them, with these toxic substances magnifying as they move up the food chain. Changes in migration and reproduction patterns and disruptions in predator-prey relationships in fish exposed to MPs can significantly affect ecological dynamics. These interconnected changes can lead to cascading effects throughout aquatic ecosystems. Thus, implementing solutions like reducing plastic production, enhancing recycling efforts, using biodegradable materials, and improving waste management is essential to minimize plastic waste and its environmental impact., Competing Interests: Declaration of competing interest The authors declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article., (Copyright © 2024 The Author(s). Published by Elsevier Inc. All rights reserved.)

Knowledge about how ecological networks vary across global scales is currently limited given the complexity of acquiring repeated spatial data for species interactions. Yet, recent developments in metawebs highlight efficient ways to first document possible interactions within regional species pools. Downscaling metawebs towards local network predictions is a promising approach to using the current data to investigate the variation of networks across space. However, issues remain in how to represent the spatial variability and uncertainty of species interactions, especially for large-scale food webs. Here, we present a probabilistic framework to downscale a metaweb based on the Canadian mammal metaweb and species occurrences from global databases. We investigated how our approach can be used to represent the variability of networks and communities between ecoregions in Canada. Species richness and interactions followed a similar latitudinal gradient across ecoregions but simultaneously identified contrasting diversity hotspots. Network motifs revealed additional areas of variation in network structure compared with species richness and number of links. Our method offers the potential to bring global predictions down to a more actionable local scale, and increases the diversity of ecological networks that can be projected in space. This article is part of the theme issue 'Connected interactions: enriching food web research by spatial and social interactions'.

Spatial differences in the isotope values of widely distributed marine apex consumers may reflect geographical differences in the isotopic composition of basal resources (e.g., phytoplankton) fueling food webs (bottom-up effects) or spatial differences in the trophic ecology of the taxon of interest (top-down effects). We examined spatial variation in δ 13 C and δ 15 N values from 264 South American sea lions (SASL, Otaria flavescens) of different age classes (adults, subadults and juveniles), their putative prey consisting of pelagic and benthic coastal fishes, and particulate organic matter (POM) measured from locations situated across >2300 km of the Chilean coast (between 18°42' and 39°17' S). We used generalized least squares (GLS) models to compare the form of the relationship between δ 13 C and δ 15 N and latitude between the three functional groups. Our results show that SASL from northern, central, and southern areas were isotopically distinct, with individuals from the north having lower δ 13 C and higher δ 15 N values in comparison to individuals from the south. When the relationship for each functional group was modelled individually using GLS, results indicated that for each degree of increasing latitude δ 15 N decreased on average by 0.12‰ (POM), 0.15‰ (prey), and 0.14‰ (SASL), while δ 13 C increased by 0.06‰ (POM) and 0.05‰ in both prey and SASL. We suggest that the latitudinal differences observed in SASL δ 13 C and δ 15 N values reflect baseline isotopic variation rather than marked differences in trophic ecology of these widely distributed consumers., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024. Published by Elsevier Ltd.)