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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. Types of Harmful Algal Blooms. Diatom. Produce dense blooms leading to oxygen stress.
United States Department of Agriculture
Agricultural Research Service
Catfish Genetics Research Unit
Etiologic agents associated with drinking water outbreaks, in surface water– United States, 1989-2000 (n = 175)
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.
Mass: 950-1185 AMU
Impact: Direct Toxic to zooplankton, fish, mammals, plants
IndirectAltered food webs
Microcystin can kill fish at 60-70 ng/mL
Two clonal populations – one strain blooms
in winter, whereas the other strain blooms
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
Recently shrimp kill in Texas at <20 ng/mL!
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.
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
Produced by Prymnesium parvum (brackish water
flagellate species-grows in <2 ppt water)
Toxin structure not known, no standards available
Toxic to striped bass, channel catfish
Confirmed cases in NC, LA, and TX (USA), common
in Europe, Asia
Forms resting stages-drop salinity <1.5 ppt for control
Direct effect: toxicity?, lowered dissolved oxygen/fish kills
Indirect effect: food chain alterations
Neurological toxin affecting fish equilibria
Structure not fully resolved
Toxic to: tilapia, striped bass, catfish, killifish,
mammalian tissue culture cell line(s)
Cells densities between 800-1,500/mL in surface algal
scum during fish mortality events
Fish mortalities confirmed using clonal cultures
Confirmed mortality events in TX, AR, NC, and MS (USA)
Direct effect: fish mortalities
production is from a microbial
community, so understanding role of
bacteria, and cyanobacteria is critical.
In other consortia, bacteria can
stimulate toxin production by four-fold!
Cylindrospermopsin: documented from FL, WI (USA), common in
Europe, Australia, Africa
Producers: Cylindrospermopsis raciborski, Uzbecka spp.
Saxitoxin: documented from AL water reservoirs, common in Europe
Producers: benthic Lyngbya, Anabaena species
Bioactive peptides: serine/threonine inhibitors, neurotoxins/cytotoxins
Producers: Microcystis, Oscillatoria, Nostoc
and recognition of a
bloom often occurs
late, even after the
sensor on a Piper
by CALMIT, Univ.
Cost : 10K
Hand held sensors:
if dual-head – no worries of atmospheric
correction- can be used in most weather!
cost - $7 – 90K
quick – 18 ponds in 1 hr!
features from catfish
705nm suspended solids MAX
676nm chl a trough
624nm phycocyanin trough
a necessary step for Case 2 waters, it is
possible to improve model performance.
questions. For instance, counting
potentially toxic algae does
not tell you if toxins are present,
and measuring toxins does not
tell which species are involved.