SENSING QUATERNARY CLIMATE CHANGE THROUGH HYDROLOGY: THE OSTRACODE CONNECTION

Ostracodes are sensitive to climate change only to the degree their aquatic environment responds to climate change. The three most common climate-driven environmental variables that ostracodes respond to include solute concentration, solute composition, and water depth. Water depth is probably the most ecologically complicated variable, and appears to be related to the depth of the photic zone and the presence or absence of aquatic vegetation necessary for most nektonic (swimming) species. Of course, many non-climatic factors impact the hydrology of lakes, such as geomorphology, and the mineralogy of the watershed. When many lakes are assessed regionally, however, the impact of climate (as sensed by ostracodes) overrides these other factors. To assess the sensitivity of ostracodes to climate, I visually compared the biogeography of several common ostracodes with maps of vegetation-based ecoregions, and effective moisture. The ostracode biogeography is based on data in the North American Non-Marine Ostracode Dataset (NANODe), and is limited to most of the lower 48 United States. To underscore the importance of water chemistry, I plotted the presence/absence of ostracodes with respect to solute composition and concentration. Several ostracodes occur in specific ecoregions. This suggests that ostracode assemblages and vegetation have common key environemental factors: temperature and effective moisture. PCA analyses of Quaternary ostracode and pollen records from the same cores from Illinois indicate that this relationship is in tune temporally with respect to both glacial/interglacial transitions, as well as more subtle climatic changes within shorter time frames such as the Holocene.