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Generating ecotoxicity information on microcystins and prymnesins: A different approach (SETAC 2018)
Citation:
Lazorchak, Jim, H. Herman, N. Dugan, Joel Allen, T. Sanan, AND C. Nietch. Generating ecotoxicity information on microcystins and prymnesins: A different approach (SETAC 2018). 2018 SETAC Europe, Rome, ITALY, May 13 - 17, 2018.
Impact/Purpose:
This presentation will present the latest progress on generating toxicity information for algal toxins using standard test species plus a new test species, the mayfly N. triangulifer. It is also looking at the issue in addition to toxin effects also shape effects on feeding.
Description:
There is a lack of information for estimating safe levels for aquatic life concerning the toxicity of natural toxins produced by cyanobacteria and algae. Current literature indicates the LC50s for Microcystin LR range from 1 – 21 mg/L. There is even less ecotoxicity information available for prymnesin which is produced from the estuarine golden algae Prymnesium parvum that has invaded freshwater systems in the U.S., even though there have been numerous fish kills recorded in inland Texas lakes and blooms in freshwater systems in 10 other states. Given the uncertainty and impurities of existing standards for bacteria and algal toxins and their cost of using them to conduct acute and chronic toxicity a new approach is proposed using pure cultures and ambient bloom samples. Herrera, Echeverri and Ferrao-Filho (2015) conducted acute and chronic toxicity tests on several different cladoceran species using lyophilized phytoplankton samples collected from hyrdroelectric/drinking water reservoirs in Brazil. They found that reservoir samples with higher microcystin contents were the most toxic ones and that different cladocerans had different sensitivities to microcystin. In this study we have taken a similar approach but we used laboratory cultures of a toxic unicellular Microcystis aeruginosa, non-toxin producing filamentous Anabaena flos-aquae and P parvum. Each culture was centrifuged to remove each species from its culture media, then resuspended in moderately hard water. The toxin culture, M aeruginosa was then frozen/thawed 3 times at -80 C. The non-toxin strain was not lysed. Forty-eight hour acute tests were conducted with Ceriodaphnia dubia, Daphnia magna, Hyalella azteca and larval Pimephales promelas on both strains. A similar procedure was also used on lake water samples collected during peak bloom condition. Current results show microcystin concentrations as high as 74 ug/L did not cause any significant acute toxicity to any of the four test species. Filamentous non-toxin producer A flos-aguae caused significant mortality to N triangulifer and H azteca (only when tested in MHRW but not in RMHRW) which are both grazer feeders. Mechanism of effect is undetermined at this time. August 2017 Lake Harsha bloom sample (300,000 cells/ml > WHO high risk probability value) was not acutely toxic to any of the 4 test species. Additional P parvum acute results and microcystis chronic results will also be presented.
