Oral Presentation Freshwater Sciences 2023

Evaluating the impact of urban pond discharge to ecosystem functions and microbiomes along a subtropical urban river continuum (#345)

Audrey Goeckner 1 , Ashley Smyth 2 , Meredith Holgerson 3 , Dail Laughinghouse 4 , Forrest Lefler 4 , Alexander Reisinger 1
  1. Department of Soil, Water, and Ecosystem Sciences, University of Florida, Gainesville, FL, USA
  2. Department of Soil, Water, and Ecosystem Sciences, University of Florida Tropical Research and Education Center, Homestead, FL, United States
  3. Department of Ecology & Evolutionary Biology, Cornell University, Ithaca, NY, USA
  4. Department of Agronomy, University of Florida Ft. Lauderdale Research and Education Center, Ft. Lauderdale, FL, USA

Stormwater control measures, including stormwater ponds (SWPs), are built into the landscape to capture and process surface runoff before it flows downstream. However, the ability of SWPs to improve water quality for downstream ecosystems is not well understood with studies showing that ponds can increase the nitrogen, carbon, and algal biomass exported in outflows. To assess the impact of SWP discharge on downstream ecosystems, we studied four sites along the Braden River (Florida, USA): an unimpacted headwater site and three downstream sites flowing through a SWP-dense neighborhood and three SWPs adjacent to the river. At each site we deployed sensors (dissolved oxygen, atmospheric conditions) to estimate daily ecosystem metabolism (March 2022-March 2023). We also collected samples for water chemistry, net N2 processing rates (denitrification vs. N2-fixation), and eDNA for 16S rRNA metabarcoding during two synoptic sampling events (wet and dry seasons). We predicted that water chemistry, N-processing rates, and microbiomes will differ between SWP and river sites during the dry season, but due to more frequent hydrological connections (e.g., SWPs discharging to the river), these metrics would be more similar between SWP and river sites during the wet season. Preliminary dry season data indicate that dissolved organic matter and metabolic indices within the Braden River follow patterns predicted by the river continuum concept (RCC), shifting from humic and less productive to autochthonous and more productive moving downstream. We expect that SWP discharges in the wet season will exacerbate the patterns predicted from the RCC seen during the dry season. Typically, SWPs are built to protect downstream ecosystems. This work is among the first to quantify the effect of these ubiquitous artificial aquatic ecosystems on downstream ecological dynamics. This analysis can provide insight into the services or disservices SWPs provide to aquatic ecosystems and impacts to their ecology and biogeochemistry.