Laboratory-scale evaluation of microcystin persistence following treatment of five USEPA-registered algaecides at different temperatures
Start Date
23-5-2022 5:45 PM
End Date
23-5-2022 7:00 PM
Abstract
An increasingly warmer climate and unsustainable land-use practices have exacerbated harmful algal blooms in many water resources. Algaecides are a proven treatment to mitigate blooms, but different species and limnological variables can impact efficacy. Water temperature is a variable that affects algaecide efficacy and toxin persistence. In this experiment, microcystin-producing Planktothrix was collected from Grand Lake St. Mary’s in March 2021. Samples were exposed to five different copper and peroxide-based USEPA-registered algaecides at varying concentrations within label rate and incubated at 10°C, 15°C, and 20°C. Total and extracellular microcystins were measured 96 hours after treatment. At 10°C and lowest dosage, PAK 27® reduced total microcystins by 75% compared to the control, followed by GreenClean®Liquid (66%), Cutrine® (63%), SeClear® (55%), and Aligimycin® (40%). In most trials, the amount of total microcystins reduced decreased as temperature increased. However, GreenClean® resulted in a shift to nearly 100% extracellular microcystin at all temperatures, while PAK 27® resulted in 20% extracellular microcystins at 10° and less at higher temperatures. The other three algaecides also shifted microcystins to extracellular. In general, temperature had a greater impact on total microcystin reduction than dosage. This study provides important baseline data for the development of temperature-specific management decisions.
Laboratory-scale evaluation of microcystin persistence following treatment of five USEPA-registered algaecides at different temperatures
An increasingly warmer climate and unsustainable land-use practices have exacerbated harmful algal blooms in many water resources. Algaecides are a proven treatment to mitigate blooms, but different species and limnological variables can impact efficacy. Water temperature is a variable that affects algaecide efficacy and toxin persistence. In this experiment, microcystin-producing Planktothrix was collected from Grand Lake St. Mary’s in March 2021. Samples were exposed to five different copper and peroxide-based USEPA-registered algaecides at varying concentrations within label rate and incubated at 10°C, 15°C, and 20°C. Total and extracellular microcystins were measured 96 hours after treatment. At 10°C and lowest dosage, PAK 27® reduced total microcystins by 75% compared to the control, followed by GreenClean®Liquid (66%), Cutrine® (63%), SeClear® (55%), and Aligimycin® (40%). In most trials, the amount of total microcystins reduced decreased as temperature increased. However, GreenClean® resulted in a shift to nearly 100% extracellular microcystin at all temperatures, while PAK 27® resulted in 20% extracellular microcystins at 10° and less at higher temperatures. The other three algaecides also shifted microcystins to extracellular. In general, temperature had a greater impact on total microcystin reduction than dosage. This study provides important baseline data for the development of temperature-specific management decisions.