Water column mixing and internal phosphorus loading in the three basins of Conesus Lake, NY

Session: Finger Lakes Water Quality (1)

Isidro Bosch, State University of New York at Geneseo, [email protected]
Michael Chislock, The College at Brockport, State University of New York, [email protected]
Katelynn Warner, Depart of Biology, State University of New York , [email protected]
Karl Hanafin, Conesus Lake Association, [email protected]

Abstract

Phosphorus (P) models and empirical data indicate that internal loading of P is responsible for nearly 75% of the total P annual load in Conesus Lake. Because deltas partially separate the lake into 3 basins of different areas and maximum depths, we hypothesized that each would contribute uniquely to internal loading.  Water column monitoring with temperature arrays and sampling of hypolimnetic P was carried out during the summer seasons in 2015-2018.   The water column of the north basin (depths 10-12 m) typically mixed multiple times each season and rarely developed anoxic conditions. Hypolimnetic internal loading for 2017 was calculated to be <1% of the lake-wide total of 6190 Kg over 92 days (67.3 Kg/d, 6.73 mg P/m2/d). The central basin (hypolimnion: 6.3 x 106 m3; depths 12-14 m) accounted for 11.6% of the internal P load, but mixed fully in late August and may have contributed to late summer blooms of cyanophyta.  The south basin (hypolimnion 43.1 x 106 m3; depths of 16-18 m) contributed 88% of hypolimnetic P loading but did not mix completely until late October.  Understanding the spatial and temporal patterns of internal hypolimnetic P loading is essential to planning of cost-effective P mitigation strategies for Conesus