SUBFOSSIL OSTRACODES REVEAL ONGOING REMEDIATION EFFORTS IN CONESUS LAKE RECREATING PRE-EUROPEAN ECOSYSTEM STATE

Conesus Lake, the western-most of New York’s Finger Lakes, experienced cultural eutrophication in the mid-late twentieth century. Beginning in 1999, stakeholders have made a concerted effort to reduce nutrient loading. This has resulted in Conesus overcoming its 2002 listing as phosphorus impaired and its 2006 listing as oxygen impaired and today Conesus’ trophic status is mesotrophic. In order to determine if ongoing remediation efforts recreated pre-European ecosystem states, it is necessary to consult the geohistorical record. This study uses ostracodes, microscopic crustaceans with calcified shells, as sentinels of trophic changes extending from prior to European settlement to current remediation.

Two sediment cores were taken one from shallow waters in the north and south basins of Conesus Lake. Both sediment cores comprise more than 1.5 m of sediment. Based on previous studies, we estimate these sedimentary archives extend to the early eighteenth century, prior to permanent European settlement in the late eighteenth century.

Six species were observed in the sedimentary archives. Three species of Candona display large changes in relative abundance towards the top of both cores with Ca. ohioensis and Ca. elliptica declining towards the core-tops, while Ca. candida increases towards the core-tops. Two other species, Cypridoposis vidua and Darwinula stevensoni, also increase towards the core-tops, while Limnocythere verrucosa declines in the most recent sediments. Of the three species abundant in recent sediments, Ca. candida and Cy. vidua, were also elevated in the oldest sediments. Additionally, Ca. ohioensis and Ca. elliptica were present at low abundances in the oldest sediments and peak in abundance from 50 cm to 10 cm below the core-tops before declining. Thus, Ca. candida and Cy. vidua may be indicators of mesotrophic conditions, while Ca. ohioensis and Ca. elliptica may indicate eutrophic conditions. Future radiometric dating of sedimentary archives will allow more robust assignments of ostracodes as trophic indicators. Monitoring of live ostracodes can be used to indicate Conesus’s trophic state, while the return of Ca. candida and Cy. vidua to high abundance shows ongoing remediation has recreated a pre-European ecosystem state.