Pfiesteria Piscicida

Definition

Typically found in coastal waters from Delaware and North Carolina, this dinoflagellate (a single-celled alga) has 24 reported forms, a few of which produce toxins. Unlike typical algae, Pfiesteria is an animal and typically eats other organisms. Researchers at North Carolina State University discovered it in 1988 and are continuing research on how it affects fish and humans.

Effect on Ocean Life

According to scientific research, Pfiesteria usually exists in non-toxic forms and becomes toxic only around fish, possibly triggered by their secretions or excrement. It is not a bacterium and so does not infect the fish itself; rather it produces a powerful toxin that damages the fish's skin tissue. Fish who have been hit by the Pfiesteria toxin exhibit various symptoms; some become lethargic, and others develop bleeding sores or lesions that are ultimately fatal to the fish. Pfiesteria has killed millions of fish off of the New River and the Albemarle-Pamlico estuarine systems, including the Neuse and the Tar Rivers.

According to research done by East Carolina University, Pfiesteria does not cause health problems in people and has not been proven to increase tendency toward illness even for fishermen who work in Pfiesteria-infested waters.

Causes of Pfiesteria Outbreaks

Because Pfiesteria is toxic only in the presence of large groups of fish, conditions that increase the amount of nutrients in the water contribute to its growth and toxicity. Pfiesteria feed on algae that absorb nitrogen and phosphorus; and higher levels of these nutrients increase the number of algae, which in turn increases Pfiesteria's growth rate. Before the algae have a chance to die, fish that feed off of them also multiply, increasing Pfiesteria's tendency toward toxicity. Therefore, pollution that carries excess nutrients to the water system, such as sewage, air pollutants and fertilizers, may contribute to toxic outbreaks of Pfiesteria.

Source: US EPA