Harmful algal blooms

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

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

5. 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?

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

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

8. 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

9. 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

10. Ciguatera Fish Poisoning • Ciguatoxin

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

12. 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)

13. Ciguatera Distribution

14. 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

15. 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

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

17. 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

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

19. 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

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

21. 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

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

23. 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

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

25. 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

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

27. 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

28. 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

29. 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

30. 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!)

31. HABs: Distribution in the US

32. 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

33. Satellite images: Karenia brevis in NC, 1987

34. Staellite images: Red tide in FL, 1978

35. 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)

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

37. 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

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

39. Avian Vacuolar Myelinopathy (AVM) Normal brain AVM

40. Why Hydrilla?

41. 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.

42. Hapalosiphon fontinalis

43. Indole alkaloids vinblastine d-tubocurarin