The fish-killing organism Pfiesteria is already present in Delaware's Inland Bays, red-tide dinoflagellates are also present and "bloomed" over the summer. Now a third harmful algal species, the brown tide, also has been identified in the Inland Bays.
Dr. David Hutchins, assistant professor of oceanography in the University of Delaware Graduate College of Marine Studies, conducted a survey of the Inland Bays in June 1998 to look for the presence of brown-tide organisms. The survey, funded jointly by Delaware Sea Grant and the Center for the Inland Bays, was conducted in conjunction with the regular water sampling done by the Department of Natural Resources and Environmental Control (DNREC). Surface water was collected from 13 sites, including the Indian River, Rehoboth, and Little Assawoman bays.
Hutchins explains that brown tide (Aureococcus anophagefferens) is a kind of microscopic phytoplankton that is a harmful algal bloom species. Algae can "bloom" or reproduce so rapidly that the surface waters take on the color of the species, thus giving rise to names such as red tide or brown tide. Some algal species have devastated shellfish and eelgrass beds by forming a thick mat that is impenetrable by sunlight. The mat shades out underwater life and disrupts the entire estuarine biological community. Brown tide blooms in New York, New Jersey, Rhode Island, and Texas have caused multi-million dollar losses to fisheries and tourism industries.
"Our intention in Delaware is to be proactive by assessing the potential for brown tide blooms before they occur, rather than delaying action until they become a problem," says Dr. Bruce Richards, executive director of the Center for the Inland Bays. "This project is especially urgent because brown tide blooms have happened as close as Barnegat Bay, New Jersey, just a few miles north of Delaware."
"Although Delaware hasn't had a brown tide bloom, the organism is definitely here," Hutchins states. "Eleven samples from Indian River and Rehoboth bays were negative. However, both samples from Little Assawoman Bay showed the presence of the organism."
This winter, university scientists will carry out laboratory studies with cultured brown tide growing in water collected from several sites in the Inland Bays, to try to determine the potential for blooms and the conditions under which they might begin. They also hope to carry out the same type of experiments using culture of the red-tide organism that bloomed in Indian River Bay this summer. Next summer, doctoral student Lexia Valdes will conduct experiments, funded by the Center for the Inland Bays, to determine how changes in nitrogen:phosphorus loading ratios will affect the phytoplankton community, especially brown tide and red tide, in the Inland Bays. Pfiesteria continues to be the subject of extensive monitoring efforts by university scientists and DNREC.
"Using both laboratory and field results, we hope to be able to give managers some idea of the potential for harmful algal blooms in the bays and the conditions under which they are likely to happen," Hutchins says.