Non-Pollen Palynomorph Records of Natural (Climate-Driven) and Cultural Eutrophication
Francine M G McCarthy1, Matea Drljepan
2, Olena Volik
3, Andrea Krueger
1, Donya Danesh
4, Nicholas Riddick
1 and Caitlyn Garner
1, (1)Brock Univ, St Catharines, ON, Canada, (2)Western U, London, ON, Canada, (3)University of Waterloo, Waterloo, ON, Canada, (4)Queen's University, Kingston, ON, Canada
Contact First Author: Francine M G McCarthy; fmccarthy@brocku.ca
English Abstract:
Algal palynomorphs (
e.g. Pediastrum, dinoflagellate cysts, desmids,
Botryococcus) in lake sediments from eastern North America record Holocene variations in nutrient availability. Eutrophication promotes the preservation of organic-walled planktonic microfossils while inhibiting benthic organisms (through BOD-induced bottom water anoxia) and corroding mineralized microfossils (through lowered pH in sediments due to organic acids). Non-pollen palynomorph (NPP) analysis is thus ideally suited to studies of eutrophication. Increases in algal biomass and changes in NPP assemblages (and decreases in biodiversity) identify both natural and cultural eutrophication in cores from Sluice Pond, Massachussetts and Lake Simcoe, Ontario. Natural, climate-driven, increases in nutrient availability are associated with Holocene warming, particularly with the lowstand during the hemlock decline. Cultural eutrophication is associated with impact of indigenous North Americans as well as European colonists, clearly evident in cores from Honey Harbour (Lake Huron) and Crawford Lake, Ontario.
Because these microfossils are present in slides prepared for pollen analysis, the main impediment to the exploitation of non-pollen palynomorphs (NPP) in paleolimnological studies appears to be relatively poorly understood taxonomy and ecology. Ongoing studies aim to remedy increase awareness of these microfossils and of their relation to the algal biomass that produced them, as well as investigating the effects of taphonomy on NPP assemblages; oxidation, for instance, selectively destroys more susceptible taxa, both in-situ and during acetolysis treatment. Pollen analysts are urged to pay attention to the valuable “by-products” in their slides, and to avoid acetolysis where possible, in order to obtain the maximum benefit from palynological preparations.
