PARENT SESSION
Poster Session 3: Aquatic Ecology
Monday, August 8, 5:00 PM - 6:30 PM, Exhibit Hall 210 D, Level 2, Palais des congrès de Montréal

Changes in stable carbon isotope signatures in three temperate lakes associated with autumn lake destratification.

Campbell, Eleanor^*,1, Dawson, Amy¹, Conner, Kristina¹, Lennon, Jay¹, Faiia, Anthony¹, Cottingham, Kathryn¹, ¹ Dartmouth College, Hanover, NH, 03755

ABSTRACT- The flux of organic matter across land-water interfaces is an important aspect connecting terrestrial and aquatic systems. Recent studies have found that terrestrial carbon has an important role in lake ecosystems, particularly in supplementing in-lake production of many lakes. I studied summer – to – fall seasonal changes in three stratified north temperate lakes, where deciduous leaf drop coincides with lake destratification. I used stable carbon isotopes to observe changes in pelagic pools of carbon, sampling dissolved organic carbon (DOC), particulate organic matter (POM), and zooplankton. I hypothesized that deciduous leaf input would influence these pools, causing del ¹³C values to converge on the terrestrial signature of approximately -28‰ (O’Leary, 1981). While DOC signatures did not vary, POM and zooplankton signatures did change during the summer – to – fall transition. However, POM and zooplankton signatures departed from -28‰ and became increasingly negative by at least 5‰. The changes were likely not a response to increased leaf input. Instead del ¹³C values seemed to respond to lake destratification. Studying carbon signatures of negative in-lake carbon sources, such as recycled DIC in the hypolimnion and methane-oxidizing bacteria in the water column, would expand the understanding of summer – to – fall changes in pelagic carbon pools.

Key words: stable carbon isotope analysis, terrestrial and aquatic linkage, temperate lakes, fall seasonal changes