Multi-year effort assessing cyanoHAB growth and toxicity in lower Green Bay, Lake Michigan

Session: Beyond the Edge of the Field: Mitigating the Impacts of Nutrient Pollution on HABs (3)

Sarah Bartlett, NEW Water Green Bay Metropolitan Sewerage District , [email protected]
Erin Houghton, NEW Water Green Bay Metropolitan Sewerage District, [email protected]
Donalea Dinsmore, Wisconsin Department of Natural Resources, [email protected]
Gina LaLiberte, Wisconsin Department of Natural Resources, [email protected]

Abstract

Cyanobacterial harmful algal blooms (cyanoHABs) are a growing problem in freshwater systems worldwide. Toxin-producing blooms are well documented in the Laurentian Great Lakes but little is known about the environmental drivers of cyanoHAB growth and toxicity in Green Bay, Lake Michigan, despite the Bay’s long history of eutrophication and water quality issues. Depth discrete samples were collected 2016-2018 from six sites in lower Green Bay, including four sites in a transect moving through the designated Area of Concern, and two eastern shorelines sites - Bay Beach and Joliet Park. In addition to assessing the diversity of twenty different cyanobacterial toxins, other measured variables include pigments and nutrients. Microcystin-LR and microcystin-RR were co-dominant toxins. Peak cyanotoxin concentrations were often measured when pigment fluorescent was minimal. A toxin gradient was observed with the highest microcystin concentrations measured along the eastern shore and at the mouth of the Fox River. Similarly, pigment fluorescence and several nutrient analytes followed the toxin gradient. Efforts are ongoing to reduce nutrient pollution into the Bay and while average total phosphorus concentrations are meeting water quality standards (0.1 mg/L) in lower Green Bay, the average chlorophyll concentration in 2018 was double than that of 2016 and 2017.

Twitter handle of presenter
@slbartlett8