Harmful algal blooms

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Harmful algal blooms
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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

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Environmental impacts

• Toxic effects on organisms
• Physical impairment of fish
• Nuisance conditions from odors or discoloration
  of water or habitats

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History of HABs

• HABs are not a new phenomenon!
• Documentation of HABs goes back to ancient times
• Apparent increase of the HAB occurrence in modern
  times real or imaginary?

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Red Tide

• World-wide occurrence
• Algae
• Dinoflagellates
• Diatoms

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Brown Tide

• World-wide occurrence
• Algae
• Chrysophyta (golden-brown algae)
• Aureococcus
• Aureoumbra

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Algae associated with HABs

• 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

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Ciguatera Fish Poisoning

• Gambierdiscus toxicus (a dinoflagellate)
• Associated with weeds and coral reefs
• Optimum conditions shallow waters, 25-34C,
  25-40 ppt
• Ciguatoxin and maitotoxin

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Ciguatera Fish Poisoning

• Ciguatoxin

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Ciguatera Fish Poisoning

• Common cause of food-borne poisoning
• 50 of US seafood poisoning
• 90 - Florida and Hawaii
• Spring/Summer

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Ciguatera Fish Poisoning Vectors

• Usually large fish, bottom dwellers and reef fish
• Red snapper, Grouper, Amber Jack, Sturgeon
• Toxins
• Bioaccumulate
• Stable and heat resistant
• Lipid soluble
• Highly potent (clinical effects from lt1 mg)

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Ciguatera Distribution
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Ciguatera Fish Poisoning Symptoms in humans

• Lag time lt12 h
• Acute onset
• Early symptoms (24-48 h) Gastrointestinal
• Pain, cramping, diarrhea, vomiting
• Late symptoms
• Neurological
• Headache, toothache
• Temperature disturbance (hot-cold sensation
  reversal)
• Respiratory paralysis and seizure in severe cases
• Cardiovascular
• Heart rate abnormalities (rare), usually
  bradycardia

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Ciguatera Fish Poisoning Treatment and prevention

• Diagnosis
• Biomarkers of exposure not available
• Therapy
• Not available
• Prevention
• Complicated
• Wide range of susceptible species
• Odorless, colorless, tasteless
• Avoidance
• Large reef fish
• Avoiding roe, head, viscera

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Diarrhetic Shellfish Poisoning

• Dinoflagellates
• Dinophysis acuminata, Dinophysis fortii,
  Prorocentrum lima
• Species reported in the US but associated
  illnesses not reported
• Okadaic acids and dinophysistoxins

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Diarrhetic Shellfish Poisoning Human Symptoms

• Generally mild gastrointestinal illness
• Diarrhea, nausea, vomiting
• Rapid onset, rapid resolution
• No neurotoxic effects
• Long-term effects? (Possibly tumorigenic)
• FDA level in shellfish 0.2 ppm okadaic acid
  plus 35-methyl-okadaic acid

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Neurotoxic Shellfish Poisoning

• Karenia brevis (previously Gymnodinium breve)
• Florida, Gulf of Mexico
• Brevetoxins

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Neurotoxic Shellfish Poisoning Human Symptoms

• Similar to ciguatera poisoning
• Early symptoms Gastrointestinal
• Nausea, diarrhea, vomiting
• Late symptoms
• Neurological
• Tingling
• Numbness
• Loss of motor control
• Usually not associated with human mortality
• FDA level in fish 0.8 ppm brevitoxin-2
  equivalent

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Brevetoxins Ecological Impacts

• Massive fish kills
• Harmful to birds (pelican, seagulls, cormorants)
  and manatees

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Brevetoxins Economical Impacts

• Human health-associated impacts
• Closure of shellfish beds
• Skin and respiratory irritation to humans at the
  seashore
• Losses in commercial catch and tourism

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Paralytic Shellfish Poisoning

• Dinoflagellates
• Alexandrium spp.
• Gymnodinium spp.
• Pyrodinium spp.
• Northern Atlantic and Pacific coasts
• Temperate and tropical
• Saxitoxins

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Paralytic Shellfish Poisoning Human Symptoms

• Rapid onset (30 min)
• Absence of gastrointestinal symptoms
• Neurological symptoms
• Numbness
• Headache
• Ataxia
• Weakness
• Cranial nerve dysfunction
• Diaphragmatic paralysis
• Death by asphyxiation
• Weakness can persist for weeks

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Paralytic Shellfish Poisoning Therapy and
Prevention

• Therapy
• Not available (supportive only)
• FDA limit in fish 0.8 ppm

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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
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Amnesic Shellfish Poisoning

• Pseudo-nitzschia spp. (diatoms)
• Discovered in 1987 (Price Edward Isl., Canada)
• Domoic acid

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Amnesic Shellfish Poisoning Human Symptoms

• Early symptoms Gastrointestinal
• Nausea, vomiting, diarrhea
• CNS symptoms
• Dizziness
• Cognitive effects
• Disorientation
• Memory loss
• Delirium
• Seizures
• Agitation
• Highly variable course
• 10 with permanent neurological damage

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Domoic acid Ecological Effects

• 1991 Monterey Bay CA - gt100 pelicans and
  cormorants were found dead or suffering from
  unusual neurological symptoms
• Pseudo-nitzschia australis
• Vector Northern Anchovie

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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

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Pfiesteria in humans

• Rare
• Narcosis
• Sores
• Nausea/vomiting
• Acute short-term memory loss
• Severe cognitive impairment
• Recovery in 6-8 weeks, but may re-occur
• Most cases Chesapeake fishermen and algal
  researchers (aerosol!)

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HABs Distribution in the US
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HABs What can we do about it?

• Prevention
• Complicated
• Public awareness (negative publicity for fish
  and shellfish industry)
• Prediction
• Satellite tracking of red and brown tides
• Mathematical models predicting blooms

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Satellite images Karenia brevis in NC, 1987
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Staellite images Red tide in FL, 1978
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Freshwater HABITATSA 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)
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Hydrilla verticillata
Native to Africa, Australia, and the warmer parts
of Asia. Brought to Florida in 1959 to sell as a
plant for aquariums.
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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

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Recorded cases of AVM in south-eastern United
States
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Avian Vacuolar Myelinopathy (AVM)
Normal brain
AVM
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Why Hydrilla?
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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.

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Hapalosiphon fontinalis
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Indole alkaloids
vinblastine
d-tubocurarin