Occurrence and toxicity of the cyanobacterium Gloeotrichia echinulata in low-nutrient lakes in the northeastern United States

To date, most research on cyanobacterial blooms has focused on high-nutrient, not low-nutrient lakes. We investigated reports of the cyanobacterium Gloeotrichia echinulata in lakes with low concentrations of nitrogen and phosphorus across the northeastern United States by surveying selected oligotrophic and mesotrophic lakes during four summers. G. echinulata is a large (1–3 mm diameter) colonial cyanobacterium that may have substantial effects on low-nutrient lakes used for drinking water and recreation because it can produce the toxin microcystin-LR. We found G. echinulata in the water column of 27 out of 37 lakes we sampled in Maine, New Hampshire, New York, and Vermont. G. echinulata densities were typically low (<5 colonies L−1), but occasionally at surface scum-producing levels (up to 250 colonies L−1). G. echinulata colonies from the survey lakes exhibited detectable microcystin-LR concentrations ranging from 58 to 7,148 ng microcystin-LR g−1 dry weight colonies. If G. echinulata densities increase to bloom levels observed in eutrophic systems, our data suggest that the microcystin-LR concentrations attributable to G. echinulata may reach levels known to influence aquatic organisms and pose human health risks.