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)
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