Herbicide Degradation Across Thermal Gradients and its Role in Shaping Harmful Algal Blooms

Harmful algal blooms in Lake Erie have intensified despite reductions in fertilizer use, suggesting that additional agricultural applied chemicals may be influencing these dynamics. Atrazine, a widely used herbicide that disrupts photosynthesis, and glyphosate, an herbicide that inhibits amino acid synthesis, are two of the most commonly detected contaminants in midwestern agricultural runoff. Both of these compounds can enter aquatic systems where they alter microbial communities, nutrient cycling, and the competitive balance between cyanobacteria and other phytoplankton. Our research investigates how these chemicals behave under environmentally relevant conditions and how their degradation patterns may contribute to bloom severity and toxicity. By measuring atrazine and glyphosate concentrations across controlled temperature gradients, we are identifying the thermal conditions under which these compounds persist longest and the microbial communities most capable of metabolizing them. Our data helps to clarify whether seasonal temperature shifts influence herbicide breakdown rates and, in turn, the availability of chemical byproducts that may stimulate cyanobacterial growth. This work provides insight into how agricultural management practices, chemical selection, and climate related temperature changes may interact to shape bloom formation in Lake Erie and similar freshwater ecosystems. 

• Growth of atrazine and glyphosate degrading bacteria was analyzed under controlled laboratory conditions to assess how temperature influences biomass accumulation. For each herbicide, samples were prepared in triplicate by adding 2 µL of either atrazine or glyphosate to 3 mL of growth media.

• Prepared samples were incubated across a range of temperature conditions to stimulate environmentally relevant seasonal variation. Changes in herbicide concentration were monitored over time using a spectrophotometer. Absorbance measurements were collected at regular intervals to track changes

• All measurements were performed in triplicate to ensure reliability and reproducibility of results. This approach allowed us to compare how temperature influences the persistence of atrazine and glyphosate

Future research will help us examine microbial growth and degradation across a range of temperatures. We will also test to see whether these bacteria can metabolize other carbon and nitrogen sources. Finally, we plan to investigate how these microbes interact with HAB cyanobacteria by assessing their ability to process atrazine and glyphosate in bloom conditions.