A Limnological Analysis of Cannonsville Reservoir, NY

Abstract

ABSTRACT A limnological analysis of Cannonsville Reservoir, NY, is presented that focuses on features related to primary production. Monitoring data collected in 1995, a major drawdown year for the impoundment, and long-term data (since 1974), are evaluated. The reservoir demonstrates eutrophic characteristics in most summers, though upper mesotrophic conditions have been observed in some years. The concentration of chlorophyll is found to be the most reliable indicator of trophic state for the impoundment, as tripton (non-living particulate material) interferes with the measures of Secchi disc transparency and total phosphorus (P) concentration as indicators. Evidence is presented that the sediment resuspension process introduced tripton into the water column in 1995 as the reservoir was drawn down. Oxygen was depleted from the hypolimnion during the summer months of 1995; anoxia prevailed above the deep-water sediments for about 1 month. However, a major release of P from the sediments did not occur during this period. Evidence is presented that nitrogen became limiting to phytoplankton growth in mid-summer, and that a sink process(es) operates for die soluble reactive P released in the hypolimnion from the decomposition of organic material. Longitudinal gradients in trophic state indicators and other features of water quality prevail. Bounds for the riverine, transition, and lacustrine zones are presented; the lacustrine zone represents about 80% of the full reservoir volume.