Poster Presentation Society for Freshwater Science 2025 Annual Meeting

Flow interrupted: investigating the ecological effects of dam management on benthic invertebrates  (117709)

Abigail M. Belchior 1 , Jason Mo Bennett 1 , Lindsey Reisinger 1 , Erik J. S. Emilson 2 , Gretchen L. Lescord 1
  1. Florida LAKEWATCH Program, University of Florida, School of Forest, Fisheries, & Geomatics Sciences, Gainesville, Florida, United States of America
  2. Great Lakes Forestry Centre, Canadian Forest Service, Sault Ste. Marie, Ontario , Canada

Benthic macroinvertebrate communities are used as meaningful indicators of ecosystem quality and biodiversity in aquatic research and monitoring around the world. However, their potential for informing the management of altered waterbodies in Florida, USA, has been underexplored, limiting our understanding of how anthropogenic modifications influence aquatic ecosystems in this region. This study explores the effects of management practices induced by the aging Kirkpatrick Dam, which influences flow patterns of the Ocklawaha River and created the Rodman Reservoir, an important location for sport fishing and other recreational activities. We are interested in understanding spatial and seasonal variability in common invertebrate metrics (e.g., %EPT, richness), which may be further influenced by semi-annual drawdowns commonly used in sub-tropical ecosystems. Initial collections were conducted in October 2024 upstream, within, and downstream of the reservoir. Subsequent collections are planned for Spring and Fall 2025. Using kick-and-sweep and Ponar collections we will assess invertebrate diversity, abundance, and functional group composition. Sampling also included water quality monitoring (e.g., nutrients, dissolved oxygen, dissolved organic matter, pH) and site features. Macroinvertebrates are currently being identified to the lowest practical taxonomic level using standard identification keys. Preliminary observations suggest that reservoir habitats exhibit reduced diversity and shifts toward burrowing taxa, while upstream sites display more dynamic community structures. Downstream, functional group observations indicate declines in filter feeders and increases in collectors and gatherers, potentially reflecting altered sediment dynamics and flow regimes. Quantitative analysis of the identified taxa will provide detailed metrics on community composition and functional diversity, offering a comprehensive view of the ecological shifts driven by altered hydrological conditions. We predict that seasonal drawdowns will further influence these patterns, particularly within the reservoir, temporarily disrupting equilibria and favoring opportunistic species. However, unlike larger hydroelectric dams, the Ocklawaha drawdowns are gradual, which may mitigate impacts to the invertebrate community.