Special topic:

RED TIDES, BROWN TIDES, OTHER FISH KILLERS AND CIGUATERA

Not much in TB (one “box”), therefore more detailed notes. One of Max’s main research specialties.

Collectively known as Harmful Algal Blooms (HABs).Global in occurrence.

-Named for the appearance of the water when “blooms” of certain species of phytoplankton are present (millions of per litre), especially dinoflagellates, but HABs also include some benthic blooms (Ciguatera). Marine and freshwater.

-Known for harmful effects but harm does not always happen when water is red e.g. Noctiluca in B.C.

-Two basic types of harmful effects:

-A) Harm to humans eating shellfish, or fish in the tropics, contaminated with toxins made by the HAB organism OR

-B) Harm to marine life, such as farmed salmon and shellfish

A)Paralytic Shellfish Poisoning (PSP, “red tide” in B.C. every year)

-Potentially fatal illness from eating filter-feeding shellfish, such as mussels, clams, scallops, oysters, geoducks etc. contaminated by a nerve poison.

-Symptoms: numbness, tingling of mouth, fingers and toes, vomiting, weakness, respiratory paralysis, death (crew of Captain Vancouver, 1793)

-Nerve poison, saxitoxin, blocks sodium channels. Thousands of times more powerful as a poison than cyanide (v. similar to tetrodotoxin: pufferfish poison). No antidote but victims can be saved by artificial respiration

-Produced by dinoflagellates of the genus Alexandrium (in the tropics Pyrodinium, e.g. Philippines). Why do they make it? Cysts in sediment.

-Shellfish nerves not harmed by it. Why not?

-Shellfish concentrate it. Why keep it in high concentrations?

-Toxicity depends on how many cells they eat (bloom conc., length of exposure).

-Blooms mostly in summer (May to October or November). 5-7 year cycle.

-Shellfish lose toxin (depurate) within months (clams can hold it for one year).

Other shellfish poisoning: Amnesic shellfish poisoning (ASP), toxin from a diatom, named because of permanent short-term memory loss (PEI, 1987). More types of shellfish poisoning known, including potential cancer- causing toxins.

Ciguatera fish poisoning (CFP), tropical, coral reef areas in all oceans, e.g. Hawaii, the Caribbean, Florida. Many species of fish such as barracuda, grouper, moray eels, usually safe to eat but dangerous in some places at certain periods. All are predators (carnivores) on smaller fish that eat seaweed (herbivores). Can be big problem for tourism.

-Long illness, can be fatal but rarely. Numbness, vomiting, joint pains, respiratory paralysis.

Ciguatoxin from a dino, Gambierdiscus, that lives on the seaweed. Toxin moves up the food chain, becoming more toxic in each trophic level (“food chain amplification” – like DDT)

One year ecological study (CIDA) by Max in the eastern Caribbean, based at the Bellairs marine lab in Barbados: found it must live on seaweed, needs sunshine, shelter, hates land run-off. Also work in Hawaii, Marshall Islands.

B)Fish and shellfish killers(“Brown tides”, “Ambush predators”, others)

Fish or shellfish killed by blooms of other species. Can cause major economic losses. Two basic types:

-loss of oxygen when the bloom dies and decays (bacterial respiration while feeding on the dead matter uses up oxygen – B.O.D. = biological oxygen demand) – usually indiscriminate Marine fauna mortality (MFM)

OR

-toxins made by HAB organisms released into the water.

Natural fish kills nearly every year of Florida west coast caused by a dino’ toxin (Karenia). Mostly menhaden. Aerosol irritating to humans. Oysters may get toxic to eat.

Death of fish in shallow east coast estuaries caused by the dino Pfiesteria. Heavy media hype! “And the waters turned to blood” book, “Cell from Hell”, etc .

-Comes out of sediments when fish present. Fish often have lesions (sores).

-After the fish are killed it supposedly turns into an amoeba stage and feeds on the skin of the fish. Toxicity seems to need contact with fish.

-The toxin(s) produced also supposed to affect humans breathing the aerosol.

Human symptoms include mental confusion, irrational anger, temporary memory loss.

In BC:

Death of salmon in farms caused by members of another group of phytoplankton: Heterosigma (since the 1980s in B.C.) and, for the first time in 2002, Chattonella, blooms. Long known to be a problem in Japan’s Inland Sea. High economic costs. Combat by towing (but where to?), not feeding, enclosing netpens.

Death of oyster seed in BC seems to accompany some dino blooms (new research by Max and David Cassis).

No link to pollution in either case (may be a problem in shallow bays in Sweden and Scotland).