toxic zoospore 



and lobose ameoba. 



$ 1 billion, according to the National Oce- 

 anic and Atmospheric Administration's 

 Coastal Ocean Program. 



In North Carolina, the 1987 red tide 

 that closed shellfishing along more than 

 250 miles of shoreline during peak 

 harvest season caused $25 million in 

 losses to the seafood and tourism 

 industries, Doll says. And nationally, the 

 fishing industry alone loses $35 million 

 to $65 million per year to outbreaks of 

 red tide, brown tide, oxygen-depriving 

 algae blooms and toxic algae such as 

 Pfiesteria, says Sen. Olympia Snowe, 



Pfiesteria 



If ever a harmful alga! bloom 

 had aJekyll-and-Hyde personality, 

 it is Pfiesteria piscicida. 



From a harmless cyst that lies 

 in the sediment, this organism can 

 transform itself into a toxic di- 

 noflagellate that kills fish. JoAnn 

 Burkholder, a North Carolina Sea 

 Grant researcher who codiscovered 

 Pfiesteria, says she believes it becomes 

 toxic when it detects something that 

 the fish excrete or secrete, but she 

 has yet to identify the substance. 



"We're working very, very hard 

 to determine what it is in fish excreta 

 or secreta that stimulates Pfiesteria to 

 thisJekyll-and-Hyde transformation," 

 Burkholder says. "We don't know 

 the substance." 



R-Maine, chair of the Senate Commerce 

 subcommittee on science and fisheries. 



"Even more troubling is that 

 science cannot fully explain why this is 

 happening or how to prevent it in the 

 future," Snowe says. 



With losses of this size threatening 

 the country's coastlines, scientists are 

 searching for the causes of the increase 

 and spread of HABs. 



Some evidence points to wide- 

 spread eutrophication, which is caused 

 by excess nutrients such as nitrogen and 

 phosphorus that filter from wastewater 



Benign most of the time, the 

 organism is toxic in four of its 24 life 

 stages. Exposure to active Pfiesteria 

 cultures in the laboratory kills healthy 

 scallops and striped bass in minutes. At 

 chronic, sublethal levels, its toxins create 

 bleeding lesions and destroy the 

 epidermis of finfish and the carapace of 

 blue crabs. It can also depress fishes' 

 white blood cell counts to 20 percent of 

 normal. 



Human health effects — including 

 cognitive impairment, memory loss, 

 nausea and asthmalike distress — have 

 been linked to Pfiesteria exposure in the 

 laboratory. The effects on people who 

 work on waters affected by fish kills are 

 being studied. 



The cellular features of Pfiesteria-Wke 



treatment plants, cropland, livestock 

 facilities and urban runoff. The nutrients 

 stimulate the growth of algae and 

 aquatic plants and may contribute to the 

 proliferation of HABs. 



Climate change may be another 

 culprit, causing shifts in sea surface 

 temperature and elevation that may 

 create more suitable environments for 

 harmful algae. 



Finally, some researchers suspect 

 that heightened awareness and better 

 reporting may be partly responsible for 

 the observed increases in HABs. □ 



Perplexing Fish Killer 



organisms suggest they are among 

 the oldest living dinoflagellate 

 species, Burkholder says. Pfiesteria 

 was first reported in Nature in 1 992, 

 and it has since been linked to 

 major fish kills affecting millions of 

 fish in North Carolina's estuarine 

 waters, according to N.C. Division 

 of Water Quality figures. 



These organisms thrive in 

 poorly flushed estuaries with water 

 degraded by human sewage, animal 

 wastes and other forms of nutrient 

 overenrichment, Burkholder says. 

 But large fish kills can result from a 

 variety of causes — Pfiesteria is one, 

 low dissolved oxygen is another — 

 and they often cannot be attributed 

 to a single cause. □ —J.F.N. 



COASTWATCH 15 



