# Project Summclry 

# _EPA United States Environmental Protection Agency Research and Development Environmental Monitoring Systems Laboratory Cincinnati, OH 45268 EPAl600/SR-921079 September 1992



# A Status 

# Report on 

# Planktonic Cyanobacteria (Blue-Green Algae) and their Toxins

W.W. Carmichael

While several groups of algae can cause dense waterblooms, blue-green algae are the most common offenders. Blue-green algae

- also called cyanobacteria - are minute, singlecelled microorganisms that lack a distinct, membrane-bound nucleus but, because they contain chlorophyll, can photosynthesize.

Surface blooms or scums of cyanobacteria commonly occur during the warm, windless days of late summer and fall when water can stagnate and when there are sufficient concentrations of such nutrients as nitrogen and phosphorus. Nutrient levels that contribute to water-bloom formation
can result from runoff of fertilizers or livestock or human wastes.

While cyanobacterial blooms can affect the water's taste, odor, and appearance, they also pose a more serious problem. Most, if not all, of the
common bloom-forming cyanobacteria
can produce potent biotoxins. These toxins, formed at all stages of the organisms' growth, generally remain inside the cell until age or stress causes their release into the surrounding water. The main toxic genera include fila-

. mentous 

### Anabaena, Aphanizomenon,
, Nodularia, Nostoc, Oscil/atoria, and unicellular 

### Microcystis. More than one species within these genera can be toxic, and all toxic species can form waterblooms.

Toxic waterblooms can take place in many eutrophic (nutrient rich) to hypereutrophic lakes and ponds at temperate latitudes worldwide. They are responsible for sporadic but recurrent episodes of illness and death among wild and domestic animals. Algal toxins have also been implicated in human poisonings from certain municipal and recreational ·water supplies. This implication is important for public health officials and water management personnel who need to be aware of the significance ofthe threat to health from these water-based toxins. The fuJI report provides a comprehensive assessment of toxins from cyanobacteria and
a directory to the literature published on this subject.

. 

### This ProjectSummarywas developed by EPA's Environmental Monitoring Systems Laboratory, Cincinnati, OH, 

### to announce key findings ofthe research project that is fully documented in 

### a separate report of the same title (see Project Report ordering information 

### at**back~** 

### .- 

### Introduction

Toxic waterblooms of cyanobacteria can be found in many eutrophic to hypereutrophic lakes, ponds and riversthroughout the world (Table 1). The primary toxicoses that result from ingesting toxic cyanobacteria or their toxins include acute liver toxicosis, rapid neurotoxicosis, and gastrointestinal disturbances. Mostcases, known from wild and domestic animal poisonings, involve the first two types.They result from ingesting lethal or sublethal numbers of toxic cells from a toxic waterbloom. Most cyanobacterial poisonings result in hepatotoxicosis. The algal hepatotoxins are a related family of low-molecular-weight cyclic hepta- and pentapeptides called 

# @ Printedon RecycledPaper

### r.bhl1. Known OccurrrmcBs ofToxic Cyanobacteria in Fresh orMarine Water



### U.S.A. Califomia Colorado Florida Hawaii (marineonly) Idaho Illinois Indiana Iowa

-**,,-~** ..

_..

_..**~~.** MichiganMinnesota Mississippi Montana Nebraska Nevada New Hampshire New Mexico NewYork North Dakota Ohio Oklahoma Oregon Pennsylvania South Dakota Texas Washington Wisconsin Wyoming



### two known anatoxins: anatoxin-aand anatoxin-a(s). Anatoxin-a is a bicyclic secondary amine that blocks the postsynaptictransmission of nerve impulses by depolarizing (stimulating) the neurons that receive the signal. The mechanism is similar to what the natural chemical transmitter, acetylcholine, does in stimUlatingmuscle contraction. However, unlike acetylcholine, anatoxin-a is not physiologicallyregulated and causes continuous depolarization that leads to muscle fatigue andparalysis. Anatoxin-a(s), is an organophosphate (OP) cholinesterase inhibitor that acts like an OP pesticide overdose.Here, the toxin inhibits' the natural enzyme, acetylcholinesterase, from recycling the transmitter, acetylcholine. Both toxins produce symptoms that include muscletwitching and contraction, reduced movement, gasping respiration, cyanosis (bluish color from poorly oxygenated blood), convulsions, and death. Neuromuscularblockage of the muscles used in breathing is the most likely cause of death. Argentina Austrialia Chilo 

### Bangladesh B'lnnuda 

### Bmil

Canada Alberta 

### British Columbia Manitoba. Ontario Saskatchowan 

### Europg CzGChoslovakia Denmark Finland France 

### Germany GrGQC8 HungalY Italy Netherlands Norway Poland Portugal Russia 

### SWllden Ukraine United Kingdom



### mlcrocystlns and nodularins (Table 2). Of the peptide-toxin producing genera, Microcystls 

### Is the main offender worldwide. Animals affected by these hepatotoxlns may display weakness, anorexia, and pallor 

### ofthe extremities and mucous membranes. Since all animals in a herd or flock usually drink from the samewater supply, most members will be affected within the same time. Death occurs after liver cell architecture loss, which leads to destruction of the parenchymal cells and slnusolds of the liver. This causes lethal intrahepatic hemorrhagewithin minutes to hours or hepatic insufficiency within several hours to a few days.

Cyanobacterial neurotoxicosis results from Ingestion of toxic Anabaena, Aphanlzomenon 

### or Oscillatoria. 

### While these genera can produce peptide hepatotoxlns as well as neurotoxins, theneurotoxins act more rapidly and dominate the field and clinical syndrome. Theneurotoxins comprise two groups: anatoxins and saxitoxlns (Table 2). There are India Israel Japan New Zealand Okinawa (marineonly) PeoplesRepublic of China South Africa Thailand 

### Althoughboth toxins are respiratory neurotoxins, anatoxin-a produces a rigid neckcontracture in birds as a result of its depolarizing activity, while anatoxin-a(s) causesintense salivation and mucous nasal discharge as a result of its anticholinesterase activity. Investigatorscan use these two very different signs of poisoning inavian species to differentiate the two toxins, either in field poisonings or in laboratory assays.

Aphanizomenon 

### has been shown in some cases to produce the potent sodium channel neuromuscular blocking agents, saxitoxin and neosaxitoxin. These two neurotoxins are better known from being produced by marine dinoflagellate algae responsible for the red tide poisoning phe-**-_··,··~·_·"--·~··nomenon,** 

### paralytic shellfish -poisoning (PSP). 

### Potential for Human Poisoning

All cyanotoxins could cause death or illnesses in humans as well as in wild anddomestic animals. Yet many officials remain unconvinced of the need to monitor or regulate these toxins in municipal orrecreational water supplies. The skepticism seems to arise from the fact that, despite the presence of cyanobacteria inmany bodies of water there are no confirmed cases of human death or illness from their toxins. Several factors, which probably act incombination, may explain the lack of reported human toxicity:

• Mollusks that concentrate toxins the

way shellfish concentrate marine PSP toxins are uncommon in freshwater. Where they do exist, as in Europe, people tend not to eat freshwater shellfish, except locally. • Cyanotoxins induce lethal toxicity at

a very low concentration, but they _bave._a_.sil3el'c1Q§e

__re§pol1se Cwye.,

__., ... In other words, animals must swallow a lethal or nearly lethal dose before signs of poisoning are observable.Such high concentrations of toxin occur only when waterblooms accumulate on the water's surface, especially on the downwind shore. While this iscertainly the most dangerous for watering animals, humans often find thewaterblooms' sight and smell repulsive. • Most water supplies in North America

and Europe don't support high concentrationsof toxiccyanobacteriayearround, largely because of better water quality management and colder winters. While toxic waterblooms dooccur in some drinking water supplies, filtration and dilution reduce lev

### 2Table 2. Comparison ofToxicities of Some Biological Toxins



### Saxitoxin Aphanizomenon flos-aquae

.,.". ,." ."
, .... " .•**,"~** .,**"i''''.~';** .•**,~,,=,.&** Alexandrium sp. Toxin



### Botulinum Toxin

Tetanus Toxin

Ricin
Diphtheria Toxin

Kokoi Toxin

Tetrodotoxin

Cobra Toxin
Anatoxin-a(s)

Nodularin
Microcystin

Anatoxin-a

Amatoxin

Curare

Strychnine

Muscarin

Phallotoxin

Sodium Cyanide Source

Clostridium botulinum

Clostridium tetani

Ricinus communis
Corynebacterium diphtheriee
Phy/lobates bicolor

Arothron me/sagris

Naja naja

Anabaena flos-aquae
Nodularia spumigena
Microcystis, Anabaena, Oscil/atoria, Nostoc

Anabaena flos-aquae

Amanita sp.

Chrondodendron tomentosum

Strychnos nox-vomlce

Amanita muscaria

Amanita sp. Common Name



### (Bactlarium)
(Bacterium)


### (Castor Bean Plant)**(Bac~terium)** (Poison 

### Arrow Frog)
(PuffElr fish)
(Cyanobacteria) (Dinclflagellate)
(Cobra Snake)
(Cyanobacteria)
(Cyanobacteria)
(Cyanobacteria)

(Cyanobacteria)
(Fungus)
(Brazilian Poison Arrow 

### Plant)
(Plant)


### (Fungus)
(Fungus) LethalDose' 

### (LDso )



### 0.00003

0.0001

0.02

0.3



### 2.7

8

9



### 20

20

50

50-500

200

200-500

500

500

1100

1500-2000

10000

*The acute LDso 

### in f.lg per kg bodyweight: intra-peritoneal injection; some with mice, some with rats.

els in the finished water below those that cause acute toxicosis. Further, without sensitive detection methods it's difficult to determine how much is in the finished drinking water, and without a clear understanding of thetoxins' mechanisms of action it's difficult to determine whether they are causing subacute or chronic toxicosis in humans. 

### Effects of Low-Level Exposure The most likely threat to human health from cyanobacterial toxins is subacute and chronic toxicity. We know from research over the past 20 years what the most likely mode of death will be from a lethaldose. What we don't know is the mechanism of action for a nonlethal dose, whether from a single exposure or from chronic exposure to a drinking water sup3 ply containing a persistent toxic waterbloom. There is indirect evidence that low-level concentrations of peptide hepatotoxins in drinking water affect the liver and intestine. Recent researchshowsthat the peptide toxins are potent inhibitors of protein phosphatases type 1 and2A. This means that they are tumor promoters similar in action to okadaic acid, the causative agent of diarrhetic shellfish

·U.S.Government Printing Office: 1992 - 648·080/60109

### poisoning. Research currently underway at the National Cancer Research Institute In Tokyo shows these peptide toxins can produce liver tumors In laboratory rodents. Thus, the continuous low-dose exposure that would occur during a summertime waterbloom could possibly promote liver tumor formation in humans. 

## Recommendations for Research and Development

A. Continue efforts to develop predictive models to quantify the formation of cyanobacterial blooms. Thesa models should be developed with thought toward their use fordevisingmanagementplansfor various water bodies.B. Further research to develop measures to control eutrophication and minimize development of cyanobacteria waterblooms and scums. C. Support development of sensitive, G. Support studies on the taxonomy rapid and accurate methods for the and classification of cyanobacteria. detection of cyanotoxins. This information is critical to effecD. Support efforts to adopt standard tive communication about toxic procedures for characterization of cyanobacteria and their toxins. the cyanotoxins that would in turn H. Develop USEPA support to carry support efforts to make toxin stan- out several aspects of the work on dards available for research. cyanobacterial toxins. These inE. Support research leading to an un- elude: derstanding of the transport, fate, 1. Educate and advise Federal, State and ecological role of cyanotoxins and local public health workers and in aquatic environments. the general public on toxic cyanoF. Support studies of the physiologi- bacteria. cal and genetic mechanisms in- 2. 

### Link work on cyanotoxins with apvolved in toxin production. propriate authorities in other parts Cyanobacteria can be genetically of the world so that informationcan manipulated and studied with many be exchanged and collaborative re- 

### .ot the-same techniques

.. availabJe_.

__**~-,** 

### __ ,

__**s_E;l_aLcb_Rr.Qj~cJl;L c_~m_b~.cl§)feJoREl,q**  

### __ ._. to study molecular and cellular ge- and supported. netics of other prokaryotes.

Wayne Carmichaelis with the Wright State University, Dayton, OH 45435. RobertS. Safferman 

### is the EPA Project Officer (see below). The complete report,**entitled'~** Status Reporton Planktonic Cyanobacteria (BlueGreen Algae) and Their Toxins," (Order No. PB92- 206 259/AS; Cost: $25.00; subject to change) will be available only from: National Technical Information SeNice 5285Port RoyalRoad Springfield, VA 22161 Telephone: 703-487-4650 The EPA Project Officercan be contactedat: EnvironmentalMonitoring Systems Laboratory U.S. EnvironmentalProtection Agency Cincinnati, OH 45268



### United States Environmental Protection Agency Centerfor Environmental Research Information Cincinnati, OH 45268

Official Business PenaltyfQrPrivate Use 

### $300

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### FEES PAID EPA PERMIT No. G-35