Otsego Lake Macrobenthos Communities between 1968 and 1993: Indicators of Decreasing Water Quality

Abstract

ABSTRACT Otsego Lake is a dimictic lake that fills a depression formed by the overdeepening of the headwaters of the Susquehanna River in New York. During summer stratification, the hypolimnetic waters become oxygen depleted, which has potential impacts on the cold-water fishery and has caused changes in the distribution of profundal macroinvertebrates. Trends in water quality parameters attest to the stresses of eutrophication, and artificial alterations in water levels have negatively impacted eulittoral macrobenthos. Eulittoral species richness has decreased 27.7% from 1968–88 to 1989–93. Ephemeroptera-Plecoptera-Trichoptera species richness has decreased 56.1%. Mollusca richness 52.9%. Invertebrate biomass at all depths remained stable between 1935 and 1969, but has increased since then. In 1968 mollusks dominated the eulittoral environment, arthropods were preponderant at 4–30 m in depth, and oligochaetes claimed the deepest waters. The entire littoral benthic community is now dominated by mollusks, and oligochaetes occupy substrates at middle profundal depths at the expense of the fingernail clams and the Chironomidae.