oa Evaluating Sedimentary Proxies to Recconstruct the Occurrence and Extent of Harmful Algal Blooms (HABs)

Harmful algal blooms (HABs) have increased in the Finger Lakes region of upstate New York, threatening water quality and local ecosystems. However, the lack of long-term monitoring data makes it difficult to assess how recent bloom patterns differ from those in the past. This study evaluates sedimentary proxies as tools to reconstruct historical HAB activity in two lakes—Owasco and Skaneateles—that differ in nutrient status and bloom history. In spring 2024, sediment cores were collected from both lakes. Initial analyses include total organic carbon, C/N ratios, and bulk δ¹³C, along with lipid biomarkers to estimate the relative abundance of cyanobacteria and eukaryotic algae. These data offer insights into past phytoplankton composition and bloom conditions. Future work will incorporate compound-specific hydrogen isotope measurements and sedimentary DNA (sedDNA) metabarcoding to identify bloom-forming species and trace ecological changes more precisely. By comparing proxy signals across periods of known bloom activity and absence, we assess the reliability of these tools for reconstructing past HABs. Our findings will improve understanding of long-term bloom dynamics and help predict future risks under changing environmental conditions.