By Staff
may have
killed fish
Karlodiniumis detectedby lab tests
By MIKE VOSS
Contributing Editor
Toxin released by a dinoflagellate called karlodinium may have been a contributing factor in an Aug. 6 fish kill that left more than 3.9 million fish dead in a section of the Pamlico River.
Preliminary laboratory results from the N.C. Division of Water Quality indicated that an unusually high number of karlodinium was present in the water where the fish kill occurred. Karlodinium, a plant-like dinoflagellate, releases a toxin — karlotoxin — that damages the gills of fish and can basically cause them to suffocate, according to a news release from the Pamlico-Tar River Foundation.
Karlodinium is found more often in the Chesapeake Bay than in North Carolina waters, said Heather Jacobs, the riverkeeper for the Pamlico-Tar River, on Tuesday. In North Carolina waters, the last known fish kill caused by karlodinium occurred in the Neuse River in 2006, according to PTRF.
The team has investigated several fish kills this summer, including three in less than a week.
Most dinoflagellates are marine plankton, but they can be found in fresh-water habitats, too.
Also present in the water at the time of the fish kill was a bloom of blue-green algae also known to be toxic at times, according to the preliminary lab results.
Karlodinium and similar organisms thrive in nutrient over-enriched waters.
Nitrogen and phosphorus are among nutrients that karlodinium and similar microbes feed on, according to Paxson and PTRF.
PTRF’s news release indicates it believes that nutrient overloading in the state’s waters is just part of a larger problem in regard to water quality.
Karlodinium is more plant-like than pfiesteria piscicida, which is more animal-like, Jacobs said.
In some previous years, fish kills, which included fish with lesions, in the Pamlico and Neuse rivers, were caused by pfiesteria piscicida, a small organism, according to JoAnn Burkholder and other researchers at N.C. State University. They said pfiesteria piscicida could cause lesions on fish. Other factors such as parasites, bacteria and viruses can cause lesions or sores on fish, according to scientists.
In 2004, the National Oceanic and Atmospheric Administration awarded $53,905 to the N.C. State University Center for Applied Aquatic Ecology to examine the reproductive cycles of a toxic dinoflagellate, specifically karlodinium. Researchers plan to use the research to reduce economically disastrous fish kills.
Paxson said her team, when possible, will collect water samples containing karlodinium so researchers can continue to study the microbe. The more research conducted on karlodinium, the better the chance to understand how it affects the environment, she said.