Within-Lake Spatial Variation in Fish Sedimentary DNA Concentrations.

Huston, Grayson*, Jasmine E. Saros, Michael T. Kinnison, School of Biology and Ecology and Maine Center for Genetics in the Environment, University of Maine, Orono, ME

Detecting fish DNA from lake sediments (sedDNA) offers many opportunities to understand historical communities, but often proves more challenging than detecting other aquatic taxa. One possible contributing factor could be that fish habitat associations contribute to variable deposition and degradation of fish sedDNA. Here, we investigate how fish DNA concentrations vary spatially in lake surface sediments to determine the optimal sampling location to detect historical anadromous alewife (Alosa pseudoharengus) populations. To understand where DNA concentrates with alewives present, six paired sediment cores and water samples were collected in the summer of 2022 from Walker Pond, Maine, which has had consistent alewife runs for the past 70 years. Water samples were analyzed to confirm alewife DNA in the water column, while DNA from the top centimeter of each sediment core was compared to characterize variations in alewife DNA deposition. To clarify the effects of fish phenology and time since deposition, replicate samples will be collected in the fall of 2022 and winter 2023, following alewife emigration from the lake. Analyses of sediment and water eDNA, and sediment DNA across seasons will test whether 1) fish sedDNA is variable across habitats in association with either 2) habitat-specific shedding rates, or 3) habitat-specific degradation rates. Sediment cores yielding the highest surface sedDNA concentrations will be dated and analyzed to determine how far into the past alewives can be detected. Knowledge of spatiotemporal variation of fish sedDNA is expected to help reduce false negative detections and help improve reconstructions of historical anadromous fish ecology.