A 40,000-YEAR PALEOLIMNOLOGICAL RECORD OF BIOGEOCHEMICAL AND AQUATIC COMMUNITY CHANGES FROM SHALLOW LAKE WACCAMAW, NORTH CAROLINA, USA

Lake Waccamaw is an aquatic ecosystem known for being the largest inundated Carolina Bay and for having high ecological significance for its endemic and endangered species. The Carolina Bays have been previously studied with paleolimnological tools and have produced sediment records from these ice-free areas spanning well into the last glacial period. Here, we analyzed a sediment core spanning the last 40,000 years to reconstruct cyanobacteria changes in response to multiple periods of climate change. We measured nutrients, photosynthetic pigments, cyanotoxins and stable isotopes. The d13C, C/N and the elemental profile of the sediment core indicate non-limnologic conditions from ~30 to 40ka BP. We observed an early prolonged period of high primary producer abundance with a diverse aquatic community composed of cyanobacteria, diatoms, and algae at ~26ka BP and a second after the Younger Dryas at ~11ka BP. These periods coincided with summer insolation maxima, anoxia inferred from purple-sulfur bacteria proxies, changes in nutrient stoichiometry and cyanotoxin production. A less pronounced period with cyanobacteria dominance occurred at a winter insolation maximum during the last glacial maximum at ~23ka BP. During the middle Holocene, the organic matter content and nutrients in the sediments increased, which sustained the community dynamics but favored colonial cyanobacteria. Our data demonstrate a strong linkage between climate and cyanobacteria, suggesting that insolation maxima and wetter conditions could be triggers for cyanobacteria dominance.

Primary Presenter: Savvas Paradeisis-Stathis, Auburn University (szp0156@auburn.edu)

Authors:

Savvas Paradeisis-Stathis, Auburn University  (szp0156@auburn.edu)

Matthew Waters, Auburn University  (mnw0018@auburn.edu)