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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.

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slide1

A Brief Overview of Freshwater Harmful Algal Blooms

Paul Zimba

United States Department of Agriculture

Agricultural Research Service

Catfish Genetics Research Unit

Stoneville, MS

slide2

Types of Harmful Algal Blooms

Diatom

  • Produce dense blooms leading to oxygen stress.
    • Dinoflagellates, diatoms, raphidophytes, prymnesiophytes
    • Cyanobacteria (prokaryotic microbes)
  • Produce potent toxins—illness 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)
slide3

Agricultural Impacts

Bacteria

Chemicals

Paramecium/Protozoa

Viruses

Algae

Etiologic agents associated with drinking water outbreaks, in surface water– United States, 1989-2000 (n = 175)

5%

25%

23%

2%

2%

43%

slide4

Freshwater Toxins

  • Hepatotoxins – microcystin, cylindrospermopsin, nodularins(?)
  • Neurotoxins – anatoxin-a, prymnesin, anatoxin-a(s), saxitoxin, BMAAs??
  • Bioactive peptides (ex. anabaenopeptins, anabaenopeptilides)
  • 4)Dermal irritants(?)
slide5

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.

Mass: 950-1185 AMU

Most common

substitution sites

Impact: Direct Toxic to zooplankton, fish, mammals, plants

IndirectAltered food webs

slide6

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 <20 ng/mL!

slide7

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.

slide8

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

slide9

Prymnesin toxin

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

slide10

“Euglenophycin” produced by E. sanguinea

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)

and Argentina

Direct effect: fish mortalities

slide11

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!

slide12

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

slide13

Blooms differ (benthic,

sub-surface, surface)

and recognition of a

bloom often occurs

late, even after the

event!

slide14

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
slide15

SPOTTER/

ALIGNMENT

MOTOR

PLATFORM

SENSOR SYSTEM

slide17

Overflight using

AISA push-broom

sensor on a Piper

Saratoga operated

by CALMIT, Univ.

of Nebraska

Cost : 10K

slide18

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!

slide19

Note three pronounced

features from catfish

ponds:

705nm suspended solids MAX

676nm chl a trough

624nm phycocyanin trough

slide22

By optimizing model fit for the water body,

a necessary step for Case 2 waters, it is

possible to improve model performance.

slide24

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.