A postglacial pollen and nonsiliceous algae record from Gegoka Lake, Lake County, Minnesota

As part of a multidisciplinary investigation of the Misiano archaeological site, pollen and nonsiliceous algae were recovered from a 262 cm core from Gegoka Lake, Lake County, Minnesota. The palynomorph assemblage from Gegoka Lake records changes in local and regional vegetational and lake productivity over the past 10000 years. Pollen spectra indicate that vegetation progressed from a shrub parkland/open conifer forest, to a spruce-pine forest, to a mixed conifer-hardwood forest. Pinus banksiana/resinosa is replaced by Pinus strobus about 7000 years ago. A small rise in Gramineae in the upper 17.5 cm of the core is attributed to the expansion of wild rice (Zizania aquatica) in Gegoka Lake. Four cycles of nutrient enrichment are indicated by the Pediastrum and Scenedesmus maxima in the nonsiliceous algae record. Oscillations in the nonsiliceous algae abundance probably result from changing environmental and/or limnologic conditions. The decline in nonsiliceous algae in the upper 57.5 cm of the core suggests that there has been an apparent shift to more nutrient poor conditions in Gegoka Lake in the recent past.