harmful algal blooms
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Harmful algal blooms. What are HABs?. Algae that produce toxins Dinoflagellates Diatoms Cyanobacteria (fresh water) Very potent toxins (few cells per liter can produce toxic effects) Adversely affect overall environmental quality. Environmental impacts. Toxic effects on organisms - PowerPoint PPT PresentationTRANSCRIPT
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