Development and application of a microplate assay for toxicity testing on aquatic cyanobacteria

Development and application of a microplate assay for toxicity testing on aquatic cyanobacteria:

Abstract

Regulatory environmental risk assessment (ERA), applied to establish a protection limit for all bacterial diversity in surface waters, relies on a growth inhibition test performed upon a single species of cyanobacteria and the activated sludge respiration inhibition test (ASRIT). Recently, the ability of this approach to protect adequately for bacteria that provide important ecosystem services has been questioned and empirical data for additional species to further investigate the effectiveness of the ERA is urgently required. Here, we present the development and validation of a cost effective and time efficient microplate assay for measurement of chemicals exposure on cyanobacteria growth rate that is comparable to the traditional shake flask test. The assay has been optimised to ensure comparisons of cyanobacteria sensitivity under exponential growth are assessed across equivalent experimental conditions using phycocyanin fluorescence as a surrogate for cell density. The test system is validated using potassium dichromate and the results compared to those obtained in an OECD 201 shake flask test system. This assay is suitable for the screening of new and legacy chemicals, including antibiotics, lacking ecotoxicology data across a wide range of cyanobacteria for more comprehensive ERA.

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