DIATOM EVIDENCE OF PAST WATER QUALITY CHANGES IN ADIRONDACK SEEPAGE LAKES (NEW YORK, U.S.A.)

Diatom assemblages were studied from the surface sediments of 20 seepage lakes in Adirondack Park, New York (U.S.A.). Diatom species composition was similar to that recorded in nearby drainage lakes, but the relative proportions of the taxa were different. Canonical correspondence analysis indicated that lakewater pH, watershed area, and elevation were important environmental variables correlated with the distribution of diatom taxa. Weighted-averaging regression and calibration were used to develop a lakewater inference model using the relative abundance of diatom taxa in the surface sediments of seepage lakes. This transfer function was then applied to infer pre-industrial lakewater pH from diatoms preserved in pre-industrial sediments of 13 seepage lakes. Our data indicate that, similar to Adirondack drainage lakes, recent acidification has occurred in seepage lakes; however, the magnitude of acidification has been less in the seepage lakes.