USING LIVING AND DEAD MOLLUSKS IN THE FINGERS LAKES OF WESTERN NEW YORK TO CREATE CONSERVATION BASELINES

Skeletal remains can provide pre-human baselines in ecosystems in which human impact precedes direct monitoring. The Finger Lakes of western New York have been affected by eutrophication and introduction of fauna, yet some are undergoing remediation. Here, we examine live/dead agreement of mollusks across three Finger Lakes that span a gradient of human impact. In the summer of 2019, living communities and associated death assemblages were sampled from Honeoye Lake (mesoeutrophic- polluted), Conesus Lake (mesotrophic from remediation efforts), and Canadice Lake (mesoligotrophic- protected).

A Peterson Grab dredge was used to collect ~2L of sediment from the upper 2cm of the lake floor in the northern and southern basins of each lake. These dredges were taken in transects perpendicular to the shoreline at 10 meter intervals out to 40m in all lakes. All living macroinvertebrates (soft-bodied and shelled) from these sediments were identified to the lowest taxonomic level possible. We found 6,251 total live and dead specimens of which 4,508 (72%) were of shelled-organisms. A total of 53 taxa of live and dead specimens were found from all three lakes, including 23 shelled taxa.

Honeoye Lake contained moderate species richness (31 living and dead taxa), low evenness as it was dominated by the invasive zebra mussel (Dreissena polymorpha), but abundant shells (1,695). Conesus Lake contained the most total live and dead species (43), abundant shells (2,538), and was characterized by a more even mix of native and introduced species. Canadice Lake had high total live and dead species (40), but few shells (285), and few invasive species. Among mollusks, live/dead agreement in species and rank-abundance was high in Honeoye, intermediate in Conesus, and low in Canadice.

Human impact in the Finger Lakes predates the window of time-averaging of surficial sediments. Thus, death assemblages do not capture baselines prior to human impact. Instead, death assembles are mainly composed of introduced and eutrophic species. Live/dead agreement is high in Honeoye lake where the living community is dominated by the invasive zebra mussel and lower in Conesus and Canadice Lakes where native and oligo- to mesotrophic species are commonly found alive. Future work will focus using older subfossil remains to capture pre-human baselines.