Search for: All records

Abstract Humans increasingly dominate Earth’s natural freshwater ecosystems, but biomass production of modified ecosystems is rarely studied. We estimate potential fish total standing stock in USA reservoirs is 3.4 billion (B) kg, and approximate annual secondary production is 4.5 B kg y⁻¹. We also observe varied and non-linear trends in reservoir fish biomass over time, thus previous assertions that reservoir fisheries decline over time are not universal. Reservoirs are globally relevant pools of freshwater fisheries, in part due to their immense limnetic footprint and spatial extent. This study further shows that reservoir ecosystems play major roles in food security and fisheries conservation. We encourage additional effort be expended to effectively manage reservoir environments for the good of humanity, biodiversity, and fish conservation. 

Abstract Climate change is transforming the ecology of lakes at a rapid pace, shifting some lakes toward warmwater‐dominant habitats. As a result, warmwater fishes are increasingly becoming more prevalent in lakes where they already existed, altering the patterning and strength of species interactions. Understanding shifting species interactions (e.g., competition, predation), and the role of lake management in shaping these interactions, will be critical for lake stewardship in response to climate change. Here, we present results from an intensive 5‐year experimental removal of ~285,000 warmwater fishes from a north‐temperate lake. The goal of the experiment was to test whether warmwater fish reduction is effective for rewiring lake food webs to reverse undesirable conditions for coolwater species, leading to increased recruitment and abundance of coolwater fishes. Throughout the experiment, warmwater fishes were resilient to reductions, with biomass declines of 23% averaged across five species. Among coolwater fishes, the top predator walleye showed no biomass response, while yellow perch biomass increased by ~914%. Fish species biomass changes translated to food web shifts, including a yellow perch trophic position decline of 0.4, decreased zooplankton abundances, and increased zoobenthos abundances. Our results highlight differential species responses to a management action aimed at adapting to climate change. Despite similar thermal tolerances, two coolwater species responded differently to removal of warmwater fishes, highlighting the characteristics (e.g., life history strategies, adaptive capacity) that contribute to species resilience. Given the importance of biotic interactions, climate adaptation may need to go beyond a “one‐size‐fits‐all” approach even when species have similar thermal tolerances. 

Synchrony is broadly important to population and community dynamics due to its ubiquity and implications for extinction dynamics, system stability, and species diversity. Investigations of synchrony in community ecology have tended to focus on covariance in the abundances of multiple species in a single location. Yet, the importance of regional environmental variation and spatial processes in community dynamics suggests that community properties, such as species richness, could uctuate synchronously across patches in a metacommunity, in an analog of population spatial synchrony. Here, we test the prevalence of this phenomenon and the conditions under which it may occur using theoretical simulations and empirical data from 20 marine and terrestrial metacommunities. Additionally, given the importance of biodiversity for stability of ecosystem function, we posit that spatial synchrony in species richness is strongly related to stability. Our findings show that that metacommunities often exhibit spatial synchrony in species richness. We also found that richness synchrony can be driven by environmental stochasticity and dispersal, two mechanisms of population spatial synchrony. Richness synchrony also depended on community structure, including species evenness and beta diversity. Strikingly, ecosystem stability was more strongly related to richness synchrony than to species richness itself, likely because richness synchrony integrates information about community processes and environmental forcing. Our study highlights a new approach for studying spatiotemporal community dynamics and emphasizes the spatial 19 dimensions of community dynamics and stability.