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Generating ecotoxicity information on microcystins and prymnesins: A different approach (2020 SETAC)
Citation:
Lazorchak, Jim, H. Haring, W. Thoeny, Mohamed Ghorab, J. Jones, N. Dugan, Joel Allen, T. Sanan, C. Nietch, AND Dan Tettenhorst. Generating ecotoxicity information on microcystins and prymnesins: A different approach (2020 SETAC). 2020 SETAC North America Annual Meeting, Virtual, November 15 - 19, 2020.
Impact/Purpose:
Present results of algal toxin testing
Description:
There is a lack of information to estimate safe levels for aquatic life concerning the toxicity of natural toxins produced by cyanobacteria and the freshwater invasive microalgae Prymnesium parvum. Given the uncertainty of standards for toxins, the cost of using them to conduct acute and chronic toxicity tests and their potential impurities, a new approach is proposed using cultures and ambient samples. In this study we have used laboratory cultures of a toxin producing unicellular Microcystis aeruginosa and P parvum and non-toxin producing filamentous Anabaena flos-aquae. Each culture was centrifuged to remove each species from its culture media, then resuspended in moderately hard water. The M aeruginosa culture was then frozen/thawed three times at -20 C following procedures used for ELISA analyses. A similar lysing procedure was also used on lake water samples. Acute 48-hr tests and 7-day short term chronic tests were conducted with a cell density of 3.7325 X106 (2017), 4.4167 X106 (2018), 4.1610 X 106 (2019) and 1.7464 X 106 (2020) cell/ml (average microcystin concentrations 73, 52, 37, and 855 ug/L) with Ceriodaphnia dubia, Neocloeon triangulifer, Hyalella azteca and larval Pimephales promelas. A stock concentration of 1746 ug/L was prepared for 100% exposure. For all studies, exposures were conducted at 0, 6.25, 12.5, 25, 50 and 100% of the stock concentration. Microcystin concentrations in the lysed samples as high as 74 ug/L did not cause any acute toxicity greater than the lab water controls to any of the 4-test species. A flos-aquae caused mortality greater than the controls to N triangulifer. For chronic tests, 80 L of the culture M aeruginosa were used. No treatment levels exhibited any adverse survival effects in C. dubia, P. promelas or H. azteca tests. The only adverse effects noted in these tests were the sub-lethal point estimate endpoints for reproduction inhibition (IC25=30.96% [1.37X106 cells/ml]) in the C. dubia bioassay. August 2017 Lake Harsha sample (total # of cells 300,000 cells/ml) was not acutely toxic to any of the 4-test species. For chronic toxicity lake water sample, the long term lethal concentration (LC50)% was 7.81, 15.33, and 7.59 in C. dubia, P. promelas and N triangulifer tests, and IC25 were (1.03, 8.36, and 1.14 %) respectively. For P. parvum LC50s were 493,850 cells/ml for C. dubia and 121,761 cells/ml N. triangulifer.
