Finger Lakes Institute reports decade of buoy data from Owasco Lake, highlights seasonal temperature and oxygen trends

Lisa Plekner, director of the Finger Lakes Institute at Hobart and William Smith Colleges, told the Cayuga County Legislature that the institute’s long‑running buoy monitoring program on Owasco Lake now yields enough continuous records to look at decadal trends in surface temperature and seasonal water‑column dynamics.

The buoy, deployed in one of the lake’s deepest basins (about 150 feet), uses a Yellow Springs International multiparameter sonde to collect profiles roughly every 1.5 meters twice daily. Plekner said the system measures temperature, chlorophyll (a proxy for phytoplankton), turbidity and dissolved oxygen, and a wiper cleans sensors twice daily. The institute maintained a notably longer 2024 deployment than in 2023, putting the buoy in the water April 1 and keeping it in place through nearly Thanksgiving.

The data matter because thermal stratification controls nutrient and oxygen exchange between surface and bottom waters, which in turn affects where phytoplankton grow and how fish and other organisms use the water column. “We’re trying to get more information about when the stratification sets up, how long it stays, because that influences how the materials exchange,” Plekner said.

Why it matters: the Finger Lakes Institute shares the measurements publicly through a data portal that currently displays recent years of buoy output; Plekner said the team is migrating data to a new site and adding historical records so the public can access roughly a decade of temperature and other observations. Those longer records already show an increase in June surface temperatures on the order of about 2° Celsius (roughly 3–4° Fahrenheit) over the last decade and changes in seasonal patterns in July–September, though Plekner noted the decade‑scale trends are not uniformly linear.

Plekner displayed visualizations showing (1) seasonal formation and persistence of temperature layers, (2) pulses of chlorophyll (highest in June, with pulses in July and August and a notable surface productivity event in September of one year), and (3) later‑summer oxygen depletion at depth related to high productivity in the surface layers. She emphasized that the buoy data are used to inform watershed and lake‑management decisions — for example, timing and placement of remediation projects identified in the watershed’s nine‑element plan — and to prioritize streams and tributaries that deliver higher nutrient loads.

On data access and volunteers: Plekner said the institute’s portal hosts sonde outputs and stream nutrient data collected by volunteers; the institute has integrated additional datasets (including nutrient sampling started by the late Professor John Halfman) and thanked the Emerson Foundation and Cayuga County for financial support. Ben Kelly was credited with building the data portal. Plekner said some older records are still being migrated to the new portal and that, once complete, the public will be able to view and download roughly 10 years of surface temperature and other variables.

Questions from legislators focused on whether the buoy measures nutrient loading (it does not; nutrient monitoring is a separate program) and on comparisons with nearby Finger Lakes; Plekner said lake size, depth and watershed-to-surface ratio create important differences in residence time and response to watershed inputs.

Plekner closed by stressing the program’s public‑science value: long‑term, publicly available monitoring supports modeling and helps timing and placement of projects aimed at reducing nutrient inputs and limiting harmful algal blooms.

The presentation was informational only; no formal Legislature action was recorded on the buoy program at the meeting.