Palaeocological assessment of Frenchman's Bay, Ontario, using pollen and chironomid (Diptera: Chironomidae) fossils, with emphasis on human impacts

A palaeoecological assessment, representing nearly 1000 years of deposition into Frenchman's Bay, was conducted using pollen and chironomid fossils as proxy indicators of local environmental change. Emphasis was placed on human impacts.; The pollen provided a chronology and showed succession from mixed forest to pine-dominated forest and a return to mixed forest in recent times. Vegetation changes were controlled primarily by regional climate change, particularly the Little Ice Age (∼1250 to 1850 A.D.).; After 1850, rapid change occurred, following the intensification of human activities. Sediments were composed primarily of silicates, suggesting wide-scale erosion. Grasses and weeds, particularly ragweed, increased while marsh plants declined. Chironomid fossils showed decreasing diversity, dominance by few taxa and increased proportions of Chironomus, suggesting unstable, stressed, disturbed and eutrophic conditions. A decline in Tanypodinae, taxa associated with cool, lotic environments, and overall chironomid numbers was evident. In recent times, the assemblage has been dominated by generalists.