Mollusks have been collected in 650 locations in central New York State since 1966 in order to determine habitat preferences of the various species. Chemical and physical data were recorded at each locality. Three large lakes (Skaneateless, Otsego, and Oneida) were studies in detail to observe patterns of molluscan distribution. The species associated with different bottom types are tabulated. Mollusks are substrate distribution in typical environments are discussed. The lake studies show that definite relationships exist between mollusk distribution and substrate pattern. Species diversity is correlated with substrate diversity (r = 0.79) in 348 collection are that include several biotypes.
Three studies of the molluscs in Oneida Lake, New York, were compared to determine the changes between 1917 and 1967. The molluscan fauna present in 1917 was initially enriched by species immigrating from the western Great Lakes drainage after the opening of the Erie Barge Canal in 1925. In recent years, species diversity has been reduced, and one family (Pleuroceridae) has become locally extinct. Concurrently, populations of the introduced European gastropod Bithynia tentaculata (Hydrobiidae) have greatly increased and now dominate the molluscan community.
Otsego Lake is a diictic 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% h m 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.
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