PALEOLIMNOLOGICAL STUDY OF HOLOCENE SEDIMENTS IN LAKE CHAMPLAIN, USA-CANADA

Sediment accumulated in a lakebed holds information about past climate and changes in the regional environment. Piston and gravity cores retrieved in 2010 in Missisquoi and St. Albans Bays in Lake Champlain encompass the last 9,000 years of the lake’s history. Both bays are currently plagued by acute eutrophication resulting in the deposition of organic matter-rich sediment. Analysis of the 2010 cores produced results indicating that high levels of productivity in the most recent sediments (in particular since the mid 1800s) are due to human activities in the watershed. Productivity levels preceding the 1800s were variable but generally not as high as at present, and were controlled by climate and other changes in the environment of the surrounding watershed. Paleoproductivity proxy records for the two bays correlate well, showing a consistent response to changing environmental and climate conditions. The only significant discrepancy occurred after the 8.2 ka cooling event, when productivity in St. Albans Bay rebounded rapidly, whereas the record for Missisquoi Bay shows no such rebound.

Here we present data from new cores recently collected from the same locations to extend the existing records to include the Champlain Sea – Lake Champlain transition. The physical and chemical analyses that were performed include grain size, XRD, %C, %N, C/N, BSi, and stable isotopes. These variables provide information about lake productivity and organic matter sources and type over time, since the transition from a marine to lacustrine environment. The overall purpose of this project is to merge the two independent studies previously done in Missisquoi Bay and St. Albans Bay and to further understand/explain both the similarities and discrepancies we observed between the sedimentary records of these two highly productive areas of Lake Champlain.