Freshwater Algal Toxins: Risks to Aquatic Organisms
IAAAM Archive
Margaret Cummings; Lester H. Khoo; Irina Rudik Miksa; Daljit Vudathala; Lisa A. Murphy
University of Pennsylvania School of Veterinary Medicine
Kennett Square, PA, USA


Cyanobacteria, also known as blue-green algae, are freshwater bacteria that may accumulate in surface water as "blooms" and concentrate as "scum". Occurrences of these blooms rely on many factors, but may be related to excess nutrients that enter water due to runoff from agricultural fertilizers or sewage.

Cyanobacterial toxins are known to affect either the liver (microcystins and nodularins) or the nervous system (anatoxins). Microcystins and nodularins inhibit protein phosphatases, leading to liver dysfunction and death in mammals, birds, and fish. Anatoxins cause death within minutes secondary to respiratory paralysis. The risk to domestic and wild terrestrial and aquatic species may be significant due to the dire consequences of exposure and the lack of a specific antidote for cyanobacterial toxins. Potassium permanganate has been suggested as a possible treatment for affected ponds by oxidizing the toxins, but may also kill the algae, resulting in the release of even more toxins. Accurate detection and quantitation of the cyanobacterial toxins through monitoring and surveillance can provide the ability to limit animal exposures and losses.

Experimental sublethal intraperitoneal injections of microcystins cause distinctive microscopic liver lesions in channel catfish, Ictalurus punctatus, but have been much more difficult to appreciate and document in clinical cases. This indicates that other confirmatory methods are needed for the detection and documentation of microcystins and other cyanobacterial toxins since histopathologic lesions alone are not adequate. Economically competitive methods for determination of the cyanobacterial toxins have been applied to a variety of water samples and include an enzyme-linked immunosorbent assay (ELISA) and protein phosphatase and mouse bioassays. These methods offer detection of the toxins with limited sample preparation, however they are limited by high incidences of false positive and/or false negative results. Our laboratory has been developing and validating multiresidue LC/MS detection methods for simultaneous screening for microcystins, nodularins, and anatoxins in water and animal tissues. The final stage of our study will involve surveillance of farm ponds with collection and analysis of water and sentinel fish placed in cages in these ponds.

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Margaret Cummings

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