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Harmful algal blooms

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

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Harmful algal blooms

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  1. Harmful algal blooms

  2. 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

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

  4. 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?

  5. “Red” Tide • World-wide occurrence • Algae: • Dinoflagellates • Diatoms

  6. “Brown” Tide • World-wide occurrence • Algae • Chrysophyta (“golden-brown algae”) • Aureococcus • Aureoumbra

  7. 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

  8. 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

  9. Ciguatera Fish Poisoning • Ciguatoxin

  10. Ciguatera Fish Poisoning • Common cause of food-borne poisoning • ~ 50% of US seafood poisoning • 90% - Florida and Hawaii • Spring/Summer

  11. 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 <1 mg)

  12. Ciguatera Distribution

  13. Ciguatera Fish Poisoning: Symptoms in humans • Lag time <12 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

  14. 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

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

  16. 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

  17. Neurotoxic Shellfish Poisoning • Karenia brevis (previously Gymnodinium breve) • Florida, Gulf of Mexico • Brevetoxins

  18. 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

  19. Brevetoxins: Ecological Impacts • Massive fish kills • Harmful to birds (pelican, seagulls, cormorants) and manatees

  20. 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

  21. Paralytic Shellfish Poisoning • Dinoflagellates • Alexandrium spp. • Gymnodinium spp. • Pyrodinium spp. • Northern Atlantic and Pacific coasts • Temperate and tropical • Saxitoxins

  22. 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

  23. Paralytic Shellfish Poisoning: Therapy and Prevention • Therapy • Not available (supportive only) • FDA limit in fish 0.8 ppm

  24. 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

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

  26. 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

  27. Domoic acid: Ecological Effects • 1991 Monterey Bay CA - >100 pelicans and cormorants were found dead or suffering from unusual neurological symptoms • Pseudo-nitzschia australis • Vector: Northern Anchovie

  28. 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

  29. 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!)

  30. HABs: Distribution in the US

  31. 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

  32. Satellite images: Karenia brevis in NC, 1987

  33. Staellite images: Red tide in FL, 1978

  34. 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)

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

  36. 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

  37. Recorded cases of AVM in south-eastern United States

  38. Avian Vacuolar Myelinopathy (AVM) Normal brain AVM

  39. Why Hydrilla?

  40. 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.

  41. Hapalosiphon fontinalis

  42. Indole alkaloids vinblastine d-tubocurarin

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