PARENT SESSION
Monday, August 7, 8:00-11:30 am
COS 5 - Paleoecology
L-12, Lobby Level, Cook Convention Center
Presiders: W Gosling
Holocene records of diatom diversity, productivity, and climatic change from Arctic lakes.
Finkelstein, Sarah*,1, Gajewski, Konrad2, Podritske, Brandi2, 1 University of Toronto, Toronto, Ontario2 University of Ottawa, Ottawa, Ontario
ABSTRACT- Paleolimnological records from three mid-Arctic lakes were used to quantify changes in diversity and productivity of diatom communities and to relate these changes to regional paleoclimatic histories. Diatom assemblages in a 4000-year record from Lake PW03 (Prescott Island) were diverse relative to paleolimnological records from other Arctic lakes; average rarefaction-estimated richness was 37 taxa per sample in this lake. Maximum diatom diversity in Lake PW03 occurred prior to 2000 years ago; diversity subsequently declined, coincident with regional climatic cooling. Diatom assemblages from a 7000-year record from Lake JR01 (Boothia Peninsula) and a 9700-year record from Lake KR02 (Victoria Island) show a similar pattern with maximum diversity in the earlier part of the records, and subsequent declines. Lakes JR01 and KR02 show highest values for diatom productivity, measured through valve concentrations and biogenic silica, in the earlier parts of the records, which correspond to maximum Holocene warmth in the central Arctic Islands. Declines in diatom productivity occurred in all records during the Little Ice Age (LIA), around 500 years ago, and small increases in diatom diversity bracket the LIA. Lake KR02 had the least diverse diatom assemblages and was dominated throughout the Holocene by small, benthic Fragilarioid types. In all three lakes, increases in diatom diversity and productivity occur in the sediments deposited over the past two centuries but values for diversity and productivity during recent times are lower than the early- or mid-Holocene maxima. The results from all three lakes indicate that disturbances associated with climatic change can increase the diversity of available diatom habitats, thereby increasing the diatom diversity in the lake. The results also indicate a close connection between regional climate and diatom productivity.
Key words: paleoecology, Arctic lakes, diversity