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The Influence of Turbidity, Light Intensity, and Temperature Stress on Microcystin-Production by Toxic Cyanobacteria in Batch Experiments and Oligotrophic Systems
Citation:
Keeton, K., T. Jicha, A. Banerji, A. Peterson, M. Lambert, AND K. Benesh. The Influence of Turbidity, Light Intensity, and Temperature Stress on Microcystin-Production by Toxic Cyanobacteria in Batch Experiments and Oligotrophic Systems. St Louis River Estuary, Duluth, MN, March 08 - 10, 2023. https://doi.org/10.23645/epacomptox.24602091
Impact/Purpose:
Harmful cyanobacterial blooms are becoming more prevalent and more toxic in Lake Superior. This project aims to protect public health by studying the effects of environmental triggers on toxin production by cyanobacteria in Lake Superior using cultures collected from a toxic bloom and subjecting them to stresses in light and temperature over varying turbidities and comparing them to observations in the field. This project will help inform predictive models for toxin-producing blooms in Barker's Island Beach, a popular swimming and recreational destination.
Description:
Cyanobacterial harmful algal blooms (CHABs) are a common occurrence in shallow eutrophic lakes, but their recent appearance in deep oligotrophic Lake Superior is a phenomenon. A toxic bloom was reported in September 2021 in Barker’s Island Beach (BIB), sparking interest in the mechanisms of toxin production in oligotrophic systems. From May – October 2022, water quality characteristics were measured on a weekly basis from 5 locations in the St. Louis River Estuary. Mean air temperatures were highest in July and lowest in June and September. Water temperatures steadily increased over the sampling period with a maximum temperature of 29.6°C in BIB. Mean chlorophyll-a (Chl a) and phycocyanin (PCY) concentrations were 14.4 µg/L and 1.02 µg/L, respectively, with the highest concentrations occurring days after precipitation events > 0.5 inches. In September 2022, a toxic CHAB occurred on the shore of BIB. Within the bloom, Chl a and PCY concentrations spiked to 126 µg/L and 28.3 µg/L, and microcystin (MC) concentration was 3.96 µg/L, whereas two meters outside of the bloom, Chl a and PCY concentrations were 45.8 µg/L and 8.67 µg/L, respectively, with no detectable levels of MC. Additionally, water temperature was nearly twice as low as the preceding week, when a sudden drop in air temperature and overcast conditions caused water temperatures to steeply decline. Given these antecedent conditions, we will subject cultures of the bloom to a gradient of light and temperature stresses over a range of varying turbidities to determine the relationships between light intensity, temperature, and toxin production. Varying turbidities will be used to mimic post-precipitation events and to decipher if any other unknown factors, in addition to light and temperature, may contribute to toxin production.
URLs/Downloads:
DOI: The Influence of Turbidity, Light Intensity, and Temperature Stress on Microcystin-Production by Toxic Cyanobacteria in Batch Experiments and Oligotrophic Systems
PRESENTATION.PDF (PDF, NA pp, 3633.922 KB, about PDF)