Harmful algal blooms

What are HABs?

Algae that produce toxinsDinoflagellatesDiatomsCyanobacteria (fresh water)

Very potent toxins (few cells per liter can produce toxic effects)

Adversely affect overall environmental quality

Environmental impacts

Toxic effects on organismsPhysical impairment of fishNuisance conditions from odors or

discoloration of water or habitats

History of HABs

HABs are not a new phenomenon!Documentation of HABs goes back to

ancient timesApparent increase of the HAB occurrence

in modern times – real or imaginary?

“Red” Tide

World-wide occurrence

Algae:DinoflagellatesDiatoms

“Brown” TideWorld-wide occurrenceAlgae

Chrysophyta (“golden-brown algae”)AureococcusAureoumbra

Toxic dinoflagellate blooms Ciguatera Fish Poisoning Diarrhetic Shellfish Poisoning Neurotoxic Shellfish Poisoning Paralytic Shellfish Poisoning

Toxic diatom blooms Amnesic Shellfish Poisoning

Harmful blooms (non-toxic or toxicity not confirmed) Fish kills

Pfiesteria, Chaetoceros, Heterosigma Brown tides

Aureococcus, Aureoumbra

Algae associated with HABs

Ciguatera Fish Poisoning

Gambierdiscus toxicus (a dinoflagellate)

Associated with weeds and coral reefs

Optimum conditions: shallow waters, 25-34°C, 25-40 ppt

Ciguatoxin and maitotoxin

Ciguatera Fish Poisoning

Ciguatoxin

Ciguatera Fish Poisoning

Common cause of food-borne poisoning~ 50% of US seafood poisoning

90% - Florida and HawaiiSpring/Summer

Ciguatera Fish Poisoning: Vectors

Usually large fish, bottom dwellers and reef fishRed snapper, Grouper, Amber Jack, Sturgeon

ToxinsBioaccumulateStable and heat resistantLipid solubleHighly potent (clinical effects from <1 mg)

Ciguatera Distribution

Lag time <12 hAcute onsetEarly symptoms (24-48 h): Gastrointestinal

Pain, cramping, diarrhea, vomitingLate symptoms

NeurologicalHeadache, toothacheTemperature disturbance (hot-cold sensation reversal)Respiratory paralysis and seizure in severe cases

CardiovascularHeart rate abnormalities (rare), usually bradycardia

Ciguatera Fish Poisoning: Symptoms in humans

Ciguatera Fish Poisoning: Treatment and prevention

DiagnosisBiomarkers of exposure not available

TherapyNot available

PreventionComplicated

Wide range of susceptible speciesOdorless, colorless, tasteless

AvoidanceLarge reef fishAvoiding roe, head, viscera

Diarrhetic Shellfish Poisoning

DinoflagellatesDinophysis acuminata,

Dinophysis fortii, Prorocentrum lima

Species reported in the US but associated illnesses not reported

Okadaic acids and dinophysistoxins

Diarrhetic Shellfish Poisoning: Human Symptoms

Generally mild gastrointestinal illnessDiarrhea, nausea, vomitingRapid onset, rapid resolutionNo neurotoxic effects Long-term effects? (Possibly tumorigenic)

FDA level in shellfish – 0.2 ppm okadaic acid plus 35-methyl-okadaic acid

Neurotoxic Shellfish Poisoning

Karenia brevis (previously Gymnodinium breve)

Florida, Gulf of Mexico

Brevetoxins

Neurotoxic Shellfish Poisoning: Human Symptoms

Similar to ciguatera poisoningEarly symptoms: Gastrointestinal

Nausea, diarrhea, vomitingLate symptoms

NeurologicalTinglingNumbnessLoss of motor controlUsually not associated with human mortality

FDA level in fish – 0.8 ppm brevitoxin-2 equivalent

Brevetoxins: Ecological Impacts

Massive fish killsHarmful to birds

(pelican, seagulls, cormorants) and manatees

Brevetoxins: Economical Impacts

Human health-associated impactsClosure of shellfish bedsSkin and respiratory irritation to humans at

the seashoreLosses in commercial catch and tourism

Paralytic Shellfish Poisoning

DinoflagellatesAlexandrium spp.Gymnodinium spp.Pyrodinium spp.

Northern Atlantic and Pacific coasts

Temperate and tropicalSaxitoxins

Paralytic Shellfish Poisoning: Human SymptomsRapid onset (~30 min)Absence of gastrointestinal symptomsNeurological symptoms

NumbnessHeadacheAtaxiaWeaknessCranial nerve dysfunctionDiaphragmatic paralysisDeath by asphyxiation

Weakness can persist for weeks

Paralytic Shellfish Poisoning: Therapy and Prevention

TherapyNot available (supportive only)

FDA limit in fish 0.8 ppm

Saxitoxins: Ecological Impacts

Mass bivalve mortality (1980- 5,000,000 mussels, 1980; 1997- 50,000, Eland Bay, South Africa)

Lobster mortality (Eland Bay, South Africa)

Humpback whales (Cape Cod, MA)1997 South Africa

Amnesic Shellfish Poisoning

Pseudo-nitzschia spp. (diatoms)

Discovered in 1987 (Price Edward Isl., Canada)

Domoic acid

Amnesic Shellfish Poisoning: Human SymptomsEarly symptoms: Gastrointestinal

Nausea, vomiting, diarrheaCNS symptoms

DizzinessCognitive effectsDisorientationMemory lossDeliriumSeizuresAgitation

Highly variable course10% with permanent neurological damage

Domoic acid: Ecological Effects

1991 Monterey Bay CA - >100 pelicans and cormorants were found dead or suffering from unusual neurological symptoms

Pseudo-nitzschia australisVector: Northern Anchovie

Pfiesteria piscicida: fish kills

Unknown substances secreted by finfish and shellfish stimulate Pfiesteria to transform from benthic cysts or amoebae or non-toxic flagellated cells, to toxic zoospores

Pfiesteria in humans

RareNarcosisSoresNausea/vomitingAcute short-term memory lossSevere cognitive impairment

Recovery in 6-8 weeks, but may re-occurMost cases – Chesapeake fishermen and

algal researchers (aerosol!)

HABs: Distribution in the US

HABs: What can we do about it?

PreventionComplicatedPublic awareness (=negative publicity for fish

and shellfish industry)

PredictionSatellite tracking of red and brown tidesMathematical models predicting blooms

Satellite images: Karenia brevis in NC, 1987

Staellite images: Red tide in FL, 1978

Freshwater HABITATS:A new “Silent Spring”?

Over 100 bald eagles found dead around man-made lakes in South Carolina, North Carolina, Texas, Arkansas and Georgia since 1995

Due to fast decay and scavengers, this may be only 10-15% of the total bald eagle deaths – therefore, estimated death toll may be as high as 1000 birds since 1995

The cause of the deaths was unknown until recently.Disease:

Avian vacuolar myelinopathy (AVM)

Hydrilla verticillata

Native to Africa, Australia, and the warmer parts of Asia. Brought to Florida in 1959 to sell as a plant for aquariums.

Hydrilla verticillata

This abundant source of biomas is a known hyperaccumulator of Mercury, Cadmium, Chromium and Lead, and as such can be used in phytoremediation

Good or bad

Recorded cases of AVM in south-eastern United States

Avian Vacuolar Myelinopathy (AVM)

Normal brain AVM

Why Hydrilla?

Hydrilla verticillata

Hydrilla verticillata and an associated epiphytic cyanobacterial species are cause of AVM.

Cyanobacteria produce the neurotoxic amino acid BMAA,

Biomagnification of BMAA occurs in wetland ecosystems

The consumption of fish and waterfowl (e.g. Canada geese and mallards) from AVM-confirmed reservoirs in Arkansas, Texas, Georgia, North Carolina and South Carolina could represent a significant human health risk.

Hapalosiphon fontinalis

Indole alkaloids

d-tubocurarin

vinblastine