DINOFLAGELLATES IN LAKE GEORGE: FROM THE WATER COLUMN TO THE LAKEBED

Dinoflagellates are an important component of the summer phytoplankton of lacustrine ecosystems, and their cysts are proving to be a very useful paleolimnological tool. The fossil record of dinoflagellates is a function of environmental conditions experienced by the motile photosynthesizing thecate stage in the epilimnion and conditions affecting preservation of cysts through the water column and on the lakebed. Using a combined phycological and palynological approach, we investigated the relationship between limnological conditions, the current phytoplankton community and the fossil record of cysts in sediments.

Sediment traps were deployed at Rensselaer’s Darrin Fresh Water Institute’s monitoring stations near Anthony’s Nose and Tea Island in the northern and southern subbasins of Lake George. Paired seasonal samplings of the water column with sediment traps provide a better understanding of the life cycle and preservation potential of common dinoflagellates, assisting in relating unknown cysts found in lakebed sediments to well-known thecate dinoflagellates. This is critical to fully identify the dinoflagellate cysts that are common in “pollen slides” processed without harsh oxidants as paleolimnological proxies. The data show that dinoflagellate assemblages in the Anthony’s Nose water column differ from Tea Island samples due to the presence of Fusiperidinium wisconsinense, an indicator of mesotrophic conditions. These differences are also reflected between cyst and green algal palynomorph assemblages in lakebed sediments at the more human impacted Tea Island site, near Lake George Village, and the less impacted Anthony’s Nose site. Overall this confirms the utility of these non-pollen palynomorphs as proxies of anthropogenic impacts.