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Marine Ecology Progress Series

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MEPS 426:213-224 (2011)  -  DOI:

Ichthyotoxicity of gymnodinioid dinoflagellates: PUFA and superoxide effects in sheepshead minnow larvae and rainbow trout gill cells

Ben D. Mooney1,*, Juan José Dorantes-Aranda1, Allen R. Place2, Gustaaf M. Hallegraeff1

1University of Tasmania, Institute for Marine and Antarctic Studies, Private Bag 55, Hobart, Tasmania 7001, Australia
2Institute of Marine and Environmental Technology, University of Maryland Center for Environmental Sciences, Baltimore, Maryland 21202, USA

ABSTRACT: While 24 h exposure of sheepshead minnow fish larvae to purified monogalactosyl diglyceride (MGDG) lipids, containing octadecapentaenoic acid (OPA) exclusively or as a mixture of octadecatetraenoic acid, eicosapentaenoic acid, and OPA (OTA-EPA-OPA), caused sluggish swimming and gulping, it produced no mortalities even at concentrations up to 120 mg l–1. In contrast, comparable concentrations and exposure times caused significant reductions in viability of rainbow trout gill cells. Pure EPA was the most harmful to gill cells (up to 98.5% viability loss in 60 h) followed by OPA-rich MGDG (45% loss), with OTA-rich MGDG (37% loss) the least toxic. OPA-pure MGDG was non-toxic to rainbow trout gill cells; however, surprisingly, pure palmitic acid was harmful (40% viability loss), and we conclude that gill cell line toxicity of the OPA-rich MGDG fraction was caused by admixture with palmitic acid. Screening of 15 Kareniaceae dinoflagellate species demonstrated that these species are low (on average 10 times less) producers of superoxide compared to the ichthyotoxic raphidophyte Chattonella marina. No mortality of sheepshead minnow fish larvae occurred when exposed to superoxide alone or superoxide combined with either OPA-rich MGDG or OTA-rich MGDG. Superoxide showed a slight impact on viability of rainbow trout gill cells. In conclusion, synergistic interactions between free fatty acids and reactive oxygen species as previously claimed for raphidophytes could not be confirmed. Gill damaging effects from EPA were conclusively demonstrated, however; when these co-occurred with OTA, a higher loss of viability was observed (up to 37%), suggesting a magnified toxic effect. Contradictory literature claims as to the ichthyotoxicity of OPA (nontoxic in our work) may relate to the presence of chemical impurities.

KEY WORDS: Kareniaceae · Ichthyotoxicity · Octadecapentaenoic acid · OPA · Polyunsaturated fatty acid · PUFA· Superoxide

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Cite this article as: Mooney BD, Dorantes-Aranda JJ, Place AR, Hallegraeff GM (2011) Ichthyotoxicity of gymnodinioid dinoflagellates: PUFA and superoxide effects in sheepshead minnow larvae and rainbow trout gill cells. Mar Ecol Prog Ser 426:213-224.

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