4700-Year History of Cyanobacteria Toxin Production in a Shallow Subtropical Lake

Cyanobacterial toxins or cyanotoxins are secondary metabolites produced by cyanobacteria and are found in water bodies around the world causing negative effects on aquatic ecosystems and human health. There are numerous environmental and biological triggers for toxin production, and the ecological role of most toxins is still being determined. Whereas cyanobacterial toxin occurrence appears to be expanding and monitoring efforts have increased in recent years, the history of toxin existence in lakes is poorly understood. Here, I report the history of the cyanotoxin, cylindrospermopsin (CYN), in sediments of hypereutrophic Lake Griffin, Florida, USA, from approximately 4700 years ago to present. The record includes three periods of toxin abundance: one associated with recent, European settlement in the watershed, and the other two during the middle to late Holocene, prior to human impacts on the lake. Each period corresponds to changes in different paleolimnological measurements suggesting drivers of CYN production have varied through time. This CYN record demonstrates the use of sediment toxin concentrations as a tool to reconstruct historic cyanobacterial toxin occurrence and shows that toxin production can occur independent of anthropogenic stressors.