Algal community responses to shallow lake dystrophication

This research details changes in lake algal community structure that occurred during dystrophication. We conducted a paleolimnological investigation of Pungo Lake, a shallow, dystrophic system near the coast of North Carolina, USA. Multiple chemical and biological proxies were measured on a sediment core, including sedimentary photosynthetic pigments, lignin-phenols, nutrients, and delta C-13. Data analysis identified three zones of algal community structure corresponding to three regimes of organic matter inputs. Predystrophic conditions represented a period of low organic inputs but substantial algal abundance (diatoms and other algal types). The period of dystrophication preceded European settlement (1850) and showed an increase in organic matter deposition, lignin, and a change in lignin type. Lignin-phenols and delta C-13 signatures of organic matter indicated that terrestrial organic matter inputs increased during this period, possibly as a result of wetland expansion. Dystrophication also corresponded to an increase in algal groups that favor low light environments (cyanobacteria and cryptophytes).