Harmful algal blooms in Sodus Bay, Lake Ontario: A comparison of nutrients, marina presence, and cyanobacterial toxins

Cyanobacteria, or blue-green algae, are prominent in freshwater systems around the world. Blooms of these organisms can be problematic as they can produce powerful toxins, lead to taste and odor events, and may contribute to hypoxia upon senescence. Sodus Bay, Lake Ontario, has experienced multiple blooms of cyanobacteria since 2010. These blooms were dominated by members of the toxin-producing genera Microcystis and Dolichospermum (Anabaena). Water samples were collected in 2011 and 2012 at eight locations around Sodus Bay and analyzed for cyanobacterial abundance and the presence of cyanobacterial toxins. Both hepatotoxic microcystin(s) and neurotoxic anatoxin-a were present in Sodus Bay over the course of the two-year study. Maximum microcystin concentrations of 24.9μg/L in 2011 and 17.6μg/L in 2012 were seen in the marina of Katlynn Harbor. To determine if marina location affected bloom events, total nitrogen and phosphorus concentrations were measured on a weekly basis at several marina and non-marina sites on the bay. While the bay-wide summer means of total phosphorus exceeded New York State guidelines of 22μg P/L each year, no differences were observed in nutrient concentrations among the different sites. This suggests the bay is well mixed relative to the sampling period and that the bloom events were likely responsive to the general elevated nutrient concentrations of the bay.