Distribution of midge remains (Diptera: Chironomidae) in Baffin Island lakes and their use in paleolimnological reconstructions.

D.R. Francis¹, I.R. Walker², A.P. Wolfe³, G.H. Miller⁴, J. Briner⁴, and Y. Axford⁴. ¹Department of Geosciences, University of Massachusetts, Amherst, MA, USA 01003, ²Department of Biology, Okanagan University College, Kelowna, BC, Canada V1V 1V7, ³Department of Earth and Atmospheric Sciences, University of Alberta, Edmonton, AB Canada T6G 2E3, ⁴Institute of Arctic and Alpine Research, University of Colorado, Boulder, CO, USA 80309

Larval head capsules of chironomids are well preserved and abundant in Arctic lake sediments. Remains deposited in the surficial sediments provide an integrated sample of the living assemblage. Head capsules were identified from surficial sediment samples from 30 lakes across Baffin Island, Canada, over three vegetation/climatic zones. Distribution of midges on Baffin Island is strongly influenced by water temperature, as has been shown in many other regions. These data have been combined with data from sites in Atlantic Canada and northeastern U.S. into a transfer function for water temperature reconstructions from fossil assemblages. Sediment cores from three Baffin Island lakes have been analyzed. These analyses provide valuable information on climate change throughout the Holocene period, and the previous interglacial period. The core data also shows that other factors may influence the distribution of some species. For example, Abiskomyia, which has brachypterous adults, does not appear in the sediment record until the late Holocene. Even though climatic conditions may have been suitable for this taxon before this time, limited dispersal ability may have prevented it from reaching the High Arctic until recently. Interestingly, Abiskomyia was not present in sediments deposited during the previous interglacial period.