Citation:

Lazorchak, J., A. Kascak, S. Goodrich, J. Fischer, S. Decelles, T. Sanan, H. Mash, J. Lu, AND I. Struewing. Acute and chronic toxicity of microcystin to four standard toxicity test organisms using lysates from large cultures of Microcystis aeruginosa. 2023 SETAC NA Annual Meeting, Louisville, KY, November 12 - 16, 2023.

Impact/Purpose:

This presentation will present our current findings for generating ecotoxicity for Microcystin. 

Description:

There is a lack of information to estimate safe exposure levels to toxins produced by cyanobacteria for freshwater aquatic life. The uncertainty in concentrations and purity of standards for cyanotoxins, and potentially their cost, challenge their use for conducting acute and chronic toxicity tests. A large batch culture method using BG-11 media has been developed to generate lysate concentrates of cyanotoxins for conducting toxicity assessments. Microcystin- producing Microcystis aeruginosa and saxitoxin-producing Dolichospermun circinale CS-337/01 with confirmed mcy genes by qPCR and RT-qPCR was used in these cultures. The M. aeruginosa culture method starts with 250 ml cultures that are used to start 1L cultures tests which in turn are used to start 20L carboy cultures. BG-11 is added weekly. For the microcystin method, after 28-days and a M aeruginosa cell density of 9.5 x106 cells/mL, the cultures were centrifuged to isolate the cyanobacteria, then resuspended in test water and freeze and thawed three times. The resultant lysate was centrifuged again to remove particulate cell material. This procedure was repeated three times and resulted in a solutions containing microcystin concentrations of 7200, 9400, and 7500 µg/L (2.5 & 2.3 x 107 cells/ml in 21 days). Large batch culture acute toxicity tests resulted in 48-hr LC50s for C. dubia and D. magna ranging from 563-687 μg/L and 560-1265 μg/L, respectively. Microcystin 48-hr LC50s for N. triangulifer was 1850 μg/L and for 72 & 96-hr LC50s ranged from 296-1456 μg/L and 586-791 μg/L, respectively. Microcystin IC25s for C. dubia, N. triangulifer, and P. promelas ranged from 4.8-57 μg/L, 134-217 134 μg/L, and 74-683 μg/L, respectively.The lysates used for testing were analyzed for congener combinations to see if there were any differences in speciation over the course of the study. Results of continued testing of the new culture methods will be presented.

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