A Brief Overview of Freshwater Harmful Algal Blooms

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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

• Produce dense blooms leading to oxygen stress.
• Dinoflagellates, diatoms, raphidophytes,
  prymnesiophytes
• Cyanobacteria (prokaryotic microbes)
• Produce 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)

Dinoflagellate

• Amnesic shellfish poisoning (ASP)

?

• Cyanobacterial Toxin Poisoning (CTP)

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Etiologic agents associated with drinking water
outbreaks, in surface water United States,
1989-2000 (n 175)
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25
23
2
2
43
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• Freshwater Toxins
• Hepatotoxins microcystin, cylindrospermopsin,
  nodularins(?)
• Neurotoxins anatoxin-a, prymnesin,
  anatoxin-a(s), saxitoxin, BMAAs??
• Bioactive peptides (ex. anabaenopeptins,
  anabaenopeptilides)
• 4) Dermal irritants(?)

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Microcystins polypeptide that has gt70
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.
Mass 950-1185 AMU
Most common substitution sites
Impact Direct? Toxic to zooplankton, fish,
mammals, plants Indirect?Altered food webs
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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 lt20 ng/mL!
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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 lt2
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 lt1.5 ppt for control Direct
effect toxicity?, lowered dissolved oxygen/fish
kills Indirect effect food chain alterations
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Euglenophycin produced by E. sanguinea Neurolog
ical 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) and
Argentina Direct effect fish mortalities
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It is important to appreciate that toxin
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!
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Other toxins 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
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Blooms differ (benthic, sub-surface, surface)
and recognition of a bloom often occurs late,
even after the event!
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• Harmful Algal Blooms include non-toxin producing
• situations
• Blooms that increase biomass above baseline
  levels-
• in Florida Bay, algal blooms of 10 µg/L exceed
  the normal
• chlorophyll concentration by 5-fold.
• Shading by planktonic algae can shade benthic
• diatom mats, resulting in replacement by
  cyanobacteria
• Dinoflagellate blooms in estuaries result in
  higher
• BOD requirements and reduce dissolved oxygen,
  resulting
• in rough fish replacing desirable species

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SPOTTER/ ALIGNMENT
MOTOR
PLATFORM
SENSOR SYSTEM
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Basic Remote Sensing principles
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Overflight using AISA push-broom sensor on a
Piper Saratoga operated by CALMIT, Univ. of
Nebraska Cost 10K
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Alternatives Hand held sensors
convenient light-weight if dual-head no
worries of atmospheric correction- can be
used in most weather! cost - 7 90K quick
18 ponds in 1 hr!
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Note three pronounced features from catfish
ponds 705nm suspended solids MAX 676nm chl a
trough 624nm phycocyanin trough
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By optimizing model fit for the water body, a
necessary step for Case 2 waters, it is possible
to improve model performance.
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It is critical to realize that one technique does
not answer all 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.
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