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A Brief Overview of Freshwater Harmful Algal Blooms Paul Zimba United States Department of Agriculture Agricultural Research Service Catfish Genetics Research Unit Stoneville, MS

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Types of Harmful Algal Blooms uProduce dense blooms leading to oxygen stress. Dinoflagellates, diatoms, raphidophytes, prymnesiophytes Cyanobacteria (prokaryotic microbes) uProduce potent toxinsillness and death via food chain or biomass accumulation. Paralytic shellfish poisoning (PSP) Diarrheal shellfish poisoning (DSP) Neurotoxic shellfish poisoning (NSP) Ciguatera fishfood poisoning (CFP) Estuary-associated syndrome (EAS) Amnesic shellfish poisoning (ASP) Dinoflagellate Diatom Cyanobacterial Toxin Poisoning (CTP)

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25% 5% 23% 43% 2% Agricultural Impacts Bacteria Chemicals Paramecium/Protozoa Viruses Algae Etiologic agents associated with drinking water outbreaks, in surface water United States, 1989-2000 (n = 175)

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Freshwater Toxins 1)Hepatotoxins microcystin, cylindrospermopsin, nodularins(?) 2)Neurotoxins anatoxin-a, prymnesin, anatoxin-a(s), saxitoxin, BMAAs?? 3)Bioactive peptides (ex. anabaenopeptins, anabaenopeptilides) 4) Dermal irritants(?)

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Microcystins: polypeptide that has >70 structural variants that alter potential toxicity by 20-fold. Principal damage to liver with inhibition of protein phosphatase 2a enzyme. Identification by enzyme inhibition, antibody binding, or HPLC/MS. Most common substitution sites Impact: Direct Toxic to zooplankton, fish, mammals, plants Indirect Altered food webs Mass: 950-1185 AMU

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Microcystin in Aquaculture Systems Microcystin can kill fish at 60-70 ng/mL Two clonal populations one strain blooms in winter, whereas the other strain blooms in summer Around 50% of all ponds have measurable microcystin levels based on survey of 485 ponds during July-August (3% of total). 1% of ponds have blooms that exceed WHO guidelines Recently shrimp kill in Texas at

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Anatoxin-a Neurotoxin that disrupts nerve conductance by irreversibly binding to Na + channels. Affected organisms include mammals, birds, and fish. Commonly produced by Anabaena, Planktothrix spp. Mass: 164 AMU, requires precolumn derivatization for HPLC identification Direct effect: paralysis, or death.

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ANATOXIN-a in Aquaculture systems Producers are from Planktothrix aghardii complex Production is limited to temperatures below 16 C Toxin detected in gut contents and water, no extraction method optimized for tissue analyses

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Prymnesin toxin Produced by Prymnesium parvum (brackish water flagellate species-grows in