Pfiesteria Piscicida

Pfiesteria Piscicida
By Connie Wood
Fall 97

The study of Pfiesteria piscicida comes under several aspects of estuary characteristics and processes. It can be found in the substrate of estuaries. Pfiesteria can change under natural influences as well as human influences. Pfiesteria is a one-celled organism called dinoflagellates. It is further identified as dinoflagellate algae. Dinoflagellates are marine protozoans in the class Dinoflagellata. They generally have 2 flagella and a cellulose envelope. Scientists believe that Pfiesteria has existed for thousands, perhaps millions, of years. It has been found in waters as far north as Delaware and as far south s the Gulf of Mexico. It can live in salt water or fresh water.

Dr. Ed Noga and Dr. JoAnn Burkholder identified Pfiesteria piscicida in 1991. It sometimes acts like a plant and sometimes like an animal. Pfiesteria piscicida is considered polymorphic with 24 known forms. In one form it changes from an amoebae to a stealthy round cyst that hides in sediments, to a toxin producing dinoflagellate. The cyst form can change to a microbe with two tails and discharges toxins in the presence of fish. It reproduces while eating. Pfiesteria piscicida can then change into harmless, colorless amoebae or into a cyst that sinks back into the sediments. In another form Pfiesteria piscicida can steal the green coloration from algae and within three minutes increase it size 20 fold. Pfiesteria piscicida appears to proliferate and take on a deadly form when exposed to high levels of nitrogen and phosphorus. These chemicals are found in human and animal wastes. This fact has lead to the speculation that development of such industries as hog farming, dairies, chicken farming, housing development and golf courses upstream from estuaries have contributed to the presence of Pfiesteria piscicida.

The Pfiesteria piscicida produces a toxin that paralyzes fish. After the fish are immobile, the organism opens surface areas and feeds. The Pfiesteria piscicida is suspected to affect humans as well as fish. The toxin produced is water-soluble and lipid-soluble. Pfiesteria piscicida is documented to have sickened five workers in the Pocomoke River in Maryland. Dr. JoAnn Burkholder and her assistant, Howard Glasglow, of North Carolina University have reported illness as the result of contact with the organism. Symptoms include nausea, disorientation and memory loss.

Pfiesteria piscicida was confirmed in the field on May 23, 1991 at the Pamlico-Albermarle Sound in North Carolina after a fish kill counted in the thousands. It has was also confirmed for Pocomoke River in Maryland. The presence of Pfiesteria piscicida was reported at fish kills in June of 1997 at the Indian River in Delaware.

Pfiesteria piscicida seems to be specific to when and where it changes into a toxin producing form resulting in fish kills in estuaries and bays. The time frame for the Neuse and New Rivers fish kills in North Carolina were June through October.

Many questions are unanswered about Pfiesteria piscicida. One of the most common questions is whether the increase animal and human waste in rivers and estuaries has tipped the balance in favor or such toxic organisms. An important point is that the organism has been identified and studies are being done through universities and environmental agencies. Abstracts on studies can be located on the URL:

http://www2.ncsu.edu/unity/lockers/project/new/innews/1997/fact.htm

http://www.mdsg.umd.edu/fish-health/pfiesteria/abstracts.html

Images of Pfiesteria piscicida can be found at the following URL:

http://www2.ncsu.edu/unity/lockers/projects/aquatic-botany/pfiest.html

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