Explore the vast range of titles available.

Freshwater ecosystems and their biodiversity are presently seriously threatened by global development and population growth, leading to increases in nutrient inputs and intensification of eutrophication-induced problems in receiving fresh waters, particularly in lakes. Climate change constitutes another threat exacerbating the symptoms of eutrophication and species migration and loss. Unequivocal evidence of climate change impacts is still highly fragmented despite the intensive research, in part due to the variety and uncertainty of climate models and underlying emission scenarios but also due to the different approaches applied to study its effects. We first describe the strengths and weaknesses of the multi-faceted approaches that are presently available for elucidating the effects of climate change in lakes, including space-for-time substitution, time series, experiments, palaeoecology and modelling. Reviewing combined results from studies based on the various approaches, we describe the likely effects of climate changes on biological communities, trophic dynamics and the ecological state of lakes. We further discuss potential mitigation and adaptation measures to counteract the effects of climate change on lakes and, finally, we highlight some of the future challenges that we face to improve our capacity for successful prediction.

Food availability is the primary limitation for terrestrial Arctic predators, many of which rely on rodents that fluctuate in abundance over a 3-5-year period. During rodent scarcity, predators such as Arctic foxes (Vulpes lagopus) consume alternative prey, such as migratory birds, which are plentiful during summer. In most of the Arctic these birds return south by August, but in northern Manitoba, near the southern edge of the Arctic fox distribution, large numbers of lesser snow geese (Chen caerulescens caerulescens) and Canada geese (Branta canadensis interior) persist into October. This extended availability of geese late into fall may reduce the dependence of Arctic foxes on rodents. We used stable isotope and faecal analyses to reconstruct the Arctic fox fall and winter diet and related the most probable contributions of lemmings, goose eggs and juvenile geese with changes in prey availability and fox reproduction. Geese were a potentially important component of the fall diet for Arctic foxes, especially in years with high goose productivity, but rodents were the main component of the diet in late winter, even though rodents were scarce each summer (2010-2013). Furthermore, rodent density had a greater influence on Arctic fox reproduction, which was correlated with the subsequent winter harvest, than any other variable examined. Although geese were important fall prey for Arctic foxes at the southern edge of their distribution, they did not buffer declines in availability of rodents, which were the primary prey in April when food availability is critical for Arctic fox reproduction.

Soil bacteria and fungi mediate terrestrial biogeochemical cycling, but we know relatively little about how trophic interactions influence their community composition, diversity, and function. Specifically, it is unclear how consumer populations affect the activity of microbial taxa they consume, and therefore the interaction of those taxa with other members of the microbial community. Due to its extreme diversity, studying trophic dynamics in soil is a complex feat. Seeking to address these challenges, we performed a microcosm-based consumer manipulation experiment to determine the impact of a common fungal-feeding nematode (Aphelenchus avenae) on soil microbial community composition, diversity, and activity (e.g., C cycling parameters). Fungivory decreased fungal and bacterial α-diversity and stimulated C and N cycling, possibly via cascading impacts of fungivory on bacterial communities. Our results present experimental evidence that soil trophic dynamics are intimately linked with microbial diversity and function, factors that are key in understanding global patterns in biogeochemical cycling.

Intraguild predation (IGP), that is, feeding interaction between two consumers that share the same resource species, is commonly observed in natural food webs. IGP expands vertical niche space and slows down energy flows from lower to higher trophic levels, which potentially affects the diversity and dynamics of food webs. Here, we use food-web models to investigate the effects of IGP on species diversity and ecosystem functioning. We first simulate a five-species food-web module with different strengths of IGP at the herbivore and/or carnivore level. Results show that as the strength of IGP within a trophic level increases, the biomass of its resource level increases because of predation release; this increased biomass in turn alters the energy fluxes and biomass of other trophic levels. These results are then extended by subsequent simulations of more diverse food webs. As the strength of IGP increases, simulated food webs maintain (1) higher species diversity at different trophic levels, (2) higher total biomasses at different trophic levels, and (3) larger energy fluxes across trophic levels. Our results challenge the intuitive hypothesis that food-web structure should maximize the efficiency of energy transfer across trophic levels; instead, they suggest that the assembly of food webs should be governed by a balance between efficiency (of energy transfer) and persistence (i.e., the maintenance of species and biomasses). Our simulations also show that the relationship between biodiversity and ecosystem functioning (e.g., total biomass or primary production) is much stronger in the presence of IGP, reconciling the contrast from recent studies based on food-chain and food-web models. Our findings shed new light on the functional role of IGP and contribute to resolving the debate on structure, diversity and functioning in complex food webs.

Ecological studies have rarely been performed at the community level across a large biogeographic region. Sponges are now the primary habitat-forming organisms on Caribbean coral reefs. Recent species-level investigations have demonstrated that predatory fishes (angelfishes and some parrotfishes) differentially graze sponges that lack chemical defenses, while co-occurring, palatable species heal, grow, reproduce, or recruit at faster rates than defended species. Our prediction, based on resource allocation theory, was that predator removal would result in a greater proportion of palatable species in the sponge community on overfished reefs. We tested this prediction by performing surveys of sponge and fish community composition on reefs having different levels of fishing intensity across the Caribbean. A total of 109 sponge species was recorded from 69 sites, with the 10 most common species comprising 51.0% of sponge cover (3.6—7.7% per species). Nonmetric multidimensional scaling indicated that the species composition of sponge communities depended more on the abundance of sponge-eating fishes than geographic location. Across all sites, multiple-regression analyses revealed that spongivore abundance explained 32.8% of the variation in the proportion of palatable sponges, but when data were limited to geographically adjacent locations with strongly contrasting levels of fishing pressure (Cayman Islands and Jamaica; Curaçao, Bonaire, and Martinique), the adjusted R2 values were much higher (76.5% and 94.6%, respectively). Overfishing of Caribbean coral reefs, particularly by fish trapping, removes sponge predators and is likely to result in greater competition for space between faster-growing palatable sponges and endangered reef-building corals.

We present a framework to explain how prey stress responses to predation can resolve context dependency in ecosystem properties and functions such as food chain length, secondary production, elemental stoichiometry, and cycling. We first describe the major nonspecific physiological stress mechanisms and their ecologically relevant consequences. We next synthesize the evidence for prey physiological responses to predation risk and demonstrate that they are similar across taxa and fit well within the general stress paradigm. We then illustrate the utility of our idea by applying our understanding of the ecological consequences of stress to explain how herbivore‐prey physiological antipredator responses affect ecosystem dynamics. We hypothesize that stressed herbivores should forage on plant species with higher digestible carbohydrates than should unstressed herbivores to meet heightened energy demands. Increased consumption of carbohydrate‐rich plants should reduce their relative abundance in the community, hence altering the quantity and quality of plant litter entering the detrital pool. We further hypothesize that stress should change the elemental composition and energy content of prey excreta, egesta, and carcasses that enter the detrital pool. Finally, prey stress should lower energy and nutrient conversion efficiency and hence the transfer of materials and energy up the food chain, which should, in turn, weaken the association between ecosystem productivity and food chain length.

In this study, we evaluated the isotopic niche dynamics in resident and migratory populations of facultative amphidromous fish Galaxias maculatus (Jenyns, 1842). We hypothesised that the isotopic niche space occupied by its populations differs between resident and migratory populations and among river ecosystems. To evaluate these hypotheses, we compared the isotopic niches of G. maculatus populations along the longitudinal gradient in five river systems in the central–southern Chile. Our results revealed differences among the isotopic niches of migratory and resident populations with greater diversity of carbon sources (wider isotopic niches) in amphidromous populations and narrower isotopic niche spaces in resident populations. Galaxias maculatus is a species with complex ecological characteristics that is frequently abundant in temperate river ecosystems of the Southern Hemisphere. The dynamics of its isotopic niches and carbon sources seems to strongly relate to life-history strategy employed by specific populations and mediates trophic structure and energy flow in river ecosystems where they are abundant.

This study examines the feeding ecology and trophic dynamics of the critically endangered large yellow croaker ( Larimichthys crocea ) in the differing habitats of Hong Kong and Taiwan using 18S gut content metabarcoding and stable isotope analysis. As a top predator, the large yellow croaker plays a crucial role in regulating fish populations and maintaining balance in the marine ecosystem. We found isotopic niche differences between juveniles and adults, with juveniles consuming more planktonic prey and adults more benthic species. In the more disrupted waters of Hong Kong, disrupted ontogenetic trophic transitions were observed, as adults exhibited unexpectedly low stable nitrogen isotope values, indicating prolonged consumption of prey at low trophic levels. In contrast, the relatively less impacted waters of Taiwan showed normal ontogenetic trophic transition. These findings highlight the impact of habitat degradation on large yellow croaker and underscore the urgent need for conservation measures, including stricter fishing regulations and habitat protection, to preserve this essential species and its ecological role.

Metabolism provides a basis for using first principles of physics, chemistry, and biology to link the biology of individual organisms to the ecology of populations, communities, and ecosystems. Metabolic rate, the rate at which organisms take up, transform, and expend energy and materials, is the most fundamental biological rate. We have developed a quantitative theory for how metabolic rate varies with body size and temperature. Metabolic theory predicts how metabolic rate, by setting the rates of resource uptake from the environment and resource allocation to survival, growth, and reproduction, controls ecological processes at all levels of organization from individuals to the biosphere. Examples include: (1) life history attributes, including development rate, mortality rate, age at maturity, life span, and population growth rate; (2) population interactions, including carrying capacity, rates of competition and predation, and patterns of species diversity; and (3) ecosystem processes, including rates of biomass production and respiration and patterns of trophic dynamics. Data compiled from the ecological literature strongly support the theoretical predictions. Eventually, metabolic theory may provide a conceptual foundation for much of ecology, just as genetic theory provides a foundation for much of evolutionary biology.

Background Increasing our knowledge of soil biodiversity is fundamental to forecast changes in ecosystem functions under global change scenarios. All multicellular organisms are now known to be holobionts, containing large assemblages of microbial species. Soil fauna is now known to have thousands of species living within them. However, we know very little about the identity and function of host microbiome in contrasting soil faunal groups, across different terrestrial biomes, or at a large spatial scale. Here, we examined the microbiomes of multiple functionally important soil fauna in contrasting terrestrial ecosystems across China. Results Different soil fauna had diverse and unique microbiomes, which were also distinct from those in surrounding soils. These unique microbiomes were maintained within taxa across diverse sampling sites and in contrasting terrestrial ecosystems. The microbiomes of nematodes, potworms, and earthworms were more difficult to predict using environmental data, compared to those of collembolans, oribatid mites, and predatory mites. Although stochastic processes were important, deterministic processes, such as host selection, also contributed to the assembly of unique microbiota in each taxon of soil fauna. Microbial biodiversity, unique microbial taxa, and microbial dark matter (defined as unidentified microbial taxa) all increased with trophic levels within the soil food web. Conclusions Our findings demonstrate that soil animals are important as repositories of microbial biodiversity, and those at the top of the food web harbor more diverse and unique microbiomes. This hidden source of biodiversity is rarely considered in biodiversity and conservation debates and stresses the importance of preserving key soil invertebrates. 6kheVvGhGfd4H1y_K4HwoR Video abstract