Across the US, lakes have had to limit recreational use due to increases in outbreaks of Harmful Algal Blooms (HABs).  Many of these outbreaks occur in ‘murky’ lakes that have both high concentrations of nutrients and dissolved organic matter (DOM). While nutrients are known to promote HABs, DOM, which is comprised of both nutrients and carbon, may play a key role not only by adding nutrients, but also decreasing light availability through shading.

With funding from the Ohio Department of Higher Education’s (ODHE) Harmful Algal Bloom Research Initiative (HABRI), the Williamson lab, led by PhD student Lauren Knose, conducted microcosm and mesocosm experiments to better understand the role of DOM in toxin production in cyanobacteria. Different types of DOM, including SuperHume as well as leachate from crops, wetlands, and manure, were added to water from three different sites known to support HABs (Lake Erie: Maumee Bay and Sandusky Bay, Grand Lake St Marys). Nutrient ratios and inorganic vs organic nitrogen sources were also manipulated.