Innovative method to measure response of cyanobacteria to copper exposure: implications for harmful algal research and management

Alterations to ecosystems due to human activity have altered species diversity and abundance, leading to harmful cyanobacterial blooms. As the Anthropocene progresses, pressures are expected to increase rather than decrease, underscoring the need to characterize how stressors influence cyanobacteria. Algal testing in flasks may be too slow to effectively characterize hazards, and miniaturization using microplates has been proposed as a high-throughput alternative. However, cyanobacteria have variable optimal growing conditions, and transitioning to microplate testing may inadvertently influence the interpretation of ecotoxicity. The present study compared Microcystis aeruginosa cultivated in flasks and microplates. Microcystis aeruginosa cultured in flasks and microplates was exposed to copper (Cu) to investigate whether the test chamber influenced the interpretation of ecotoxicological responses. Microcystis aeruginosa abundance and quality were characterized using flow cytometry and a microplate reader to measure chlorophyll and phycocyanin. Cyanobacteria grown in flasks and microplates exhibited comparable growth rates, and exposure to Cu showed that cell density and viability were also comparable; however, differences were observed in chlorophyll and phycocyanin concentrations. The results suggest that microplates can be used with M. aeruginosa, and that flow cytometry is useful for interpreting the effects of Cu on cell morphology and viability.