Paleolimnological investigation of the effects of post-1970 reductions of acidic deposition on an acidified Adirondack lake

A 40-cm sediment core from Big Moose Lake (Adirondack Mountains, New York, U. S. A.) was analyzed for recent changes in chrysophyte composition of chr ysophyte species to assess if legislated reductions of sulphur emissions ha ve resulted in changes in biological composition and inferred lakewater pH in this lake. This core, taken in September 1994, had a record of stratigra phic changes in chrysophyte assemblages remarkably similar to those in Pb-2 10-dated sediment cores taken in 1983 and 1988. Abrupt changes in chrysophy te stratigraphy were used to date the newest sediment core by stratigraphic correlation. We observed relatively constant composition of chrysophyte sp ecies and inferred-pH values in post-1970 sediments, which suggests that th ere has been little change in lakewater pH values despite the reductions in sulfate deposition since 1970 in the Adirondacks. These results are consis tent with recent monitoring measurements in the Adirondacks. Further resear ch is necessary to ascertain the applicability of these findings to other l akes in the Adirondacks and to determine the reasons for the lack of recove ry.