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Contributed Poster

Session: Communities: Traits And Functional Diversity

PS 5-61 - How different human impacts affect functional diversity of freshwater fish communities?

Monday, August 7, 2023
5:00 PM – 6:30 PM PDT
Location: ESA Exhibit Hall
Abstract: Freshwater environments are important for the maintenance of life on earth and are intrinsically related to human activities, thus suffering from different types of anthropogenic impacts. These impacts cause different changes to freshwater environments and aquatic fauna, modifying community composition and structure. Fish communities can be affected in diverse ways. For example, reservoirs reduce dispersal capacity, deforestation alter local habitats and reduce allochthonous input, and invasive species alter food webs. These changes commonly alter the occurrence and abundance of species, which may alter the functional diversity (FD) of these communities by selecting taxa with specific functional traits. While it is common believed that human impacts modify the functional diversity of fish communities, there is no consensus about how they impact FD. Hence, this study assess how different human activities in freshwaters affects the FD of fish communities by summarizing published evidence through a meta-analysis approach. We focused on comparing mean and deviance of control environment (natural or less impacted) and treatment (impacted) groups. A search was conducted in Web of Science and Scopus for papers published until 2022 july. Only articles that evaluated changes in the functional diversity of freshwater fish in response to an impact were selected for data extraction. With the extracted data, Standardized Mean Difference was calculated for each case, and the results were adjusted through a random effects model. In some cases, the standard deviation was estimated based on the standard error or sample size. Results based on 58 cases (8 articles) presented 6 FD indices and 6 types of impacts. In general, impacted sites exhibited lower functional dispersion than control ones. When isolating the impacts, deforestation and the presence of invasive species increased functional richness, while the synergistic effect of more than one type of impact decreased it. These positive responses highlight that there is not a single response on how fish communities change in face of human impacts. Some impacts may even provide opportunities for functionally rare species by increasing the number of microhabitats without necessarily excluding the old ones. Deforestation, for example, may increase primary productivity by increasing light availability, thus favoring a food chain based on phytoplankton without necessarily completely eliminating the source of allochthonous materials that are used as shelter or resources by other fishes. Understanding how human impacts affect the functional structure in freshwaters is necessary to predict biological responses and manage ecosystems in face of a changing world.