Facts about Pfiesteria piscicida:

  • Pfiesteria piscicida (fee-STEER-ee-uh pis-kuh-SEED-uh), first discovered in 1988, occurs naturally in the environment.
  • Laboratory research indicates pfiesteria can exist in up to 24 life stages, four of which may be toxic.
  • Pfiesteria is a type of phytoplankton known as a dinoflagellate, which means they have a whip-like tail called a flagella which allows them to propel themselves, unlike some other types of algae which can only float. Pfiesteria, though, do not perform photosynthesis and instead survive by eating other organisms, usually algae.
  • Under specific conditions, such as high nutrient levels and the presence of large schools of fish, pfiesteria's population increases. This is referred to as a "bloom." During a bloom, pfiesteria may produce toxins that numb fish, allowing the microbe to feed on them. High concentrations of pfiesteria can cause deep lesions on fish, and may kill them. Blooms exist only for short periods of time, usually a few hours at most.
  • Blooms of pfiesteria may not result in fish kills or lesions. Pfiesteria may spend its entire life feeding harmlessly on bacteria and algae. It is not well understood what environmental factors cause pfiesteria to produce harmful toxins. In the laboratory, toxic pfiesteria blooms are induced by nutrient enrichment and large amounts for fresh fish excrement.
  • Pfiesteria has been the cause of several massive fish kills in nutrient-enriched (elevated levels of phosphorus and nitrogen) estuaries along coastal North Carolina. In most of these fish kills, large schools of menhaden were present in warm, shallow, partially land-locked waters.
  • No cases of seafood poisoning have been reported from eating fish exposed to pfiesteria. Nor has there been evidence of tainted shellfish, oysters or crabs on the market. But research in this area is not extensive. Because of this uncertainty, consumers should take normal precautions and use common sense: Never eat fish that exhibit evidence of sores or disease. Do not eat fish that seem diseased or dying when caught.
  • Well-documented human health effects linked to pfiesteria have occurred in laboratory conditions where researchers were working with the organism in close proximity and in high concentrations. Others, including anglers, a water-skier and those monitoring fish kills, have also complained of skin lesions and other health effects, such as headaches, lightheadedness and short-term memory loss.
  • For information about pfiesteria, there are several good sources on the World Wide Web.
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Among them:

North Carolina State University:

Maryland Sea Grant:

Virginia Institute of Marine Science:

Sources: Maryland Sea Grant College; Maryland Department of Natural Resources