natural conditions and added inorganic 

 nitrogen and phosphorus. These forms 

 are the most likely types of growth- 

 stimulating nutrients encountered by 

 phytoplankton and Pfiesteria-like 

 dinoflagellates in the Neuse estuary. 



Paerl and Pinckney concluded that 

 reducing phytoplankton growth would 

 translate into broad water quality 

 improvements, including a decline in 

 the frequency and magnitude of algal 

 blooms, oxygen depletion, and fish 

 and shellfish deaths. 



The Neuse River, in particular, 

 would benefit from proposed nutrient- 

 reduction strategies to improve its water 

 quality and reduce fish mortality, Paerl 

 says. 



"By reducing nitrogen loading and 

 reducing the major phytoplankton 

 responses that we saw in bioassays, it's 

 likely to help minimize outbreaks of 

 Pfiesteria as well," he says. 



The results confirmed 10 years of 

 nutrient-addition experiments on the 

 Neuse River, showing the importance of 



nitrogen as a growth-limiting nutrient, 

 Paerl says. 



Exposure to Seafood 



Meanwhile, Duke University 

 scientist Patricia McClellan-Green and 

 NC State University researchers Lee Ann 

 Jaykus and David Green studied the 

 possibility of consumer health risks from 

 eating fish exposed to Pfiesteria. They 

 wanted to know if fish exposed to the 

 dinoflagellate absorb its toxin. 



The fish used in the study were 

 collected live on Sept. 3, 1996, during an 

 active kill on Northeast Creek, a tributary 

 on the upper portions of the New River. 

 The scientists used fillets — edible 

 portions of the fish — for their studies. 



The team reported that only one 

 species of fish sampled from the kill site 

 — Atlantic menhaden — had toxin in its 

 tissues. But because other dinoflagellates 

 were present in the water, the team had 

 no way of knowing whether the toxin 

 was from Pfiesteria. Other fish collected 

 at the same time — spot, striped mullet, 



croaker, Spanish mackerel, silver perch 

 and pinfish — did not appear to contain 

 toxins. 



"The fact that none of the tissues 

 from other fish was positive is very 

 encouraging," McClellan-Green says. 



The researchers are confident that 

 the test they adapted for this research can 

 be used as an early screening method for 

 fishery products and water samples 

 collected at the site of fish kills. They are 

 continuing to refine these techniques and 

 use them with other methods for detecting 

 Pfiesteria toxins in the environment. 



Rather than ending inquiries into the 

 effects of Pfiesteria, these four peer- 

 reviewed research projects help to 

 identify areas that need further explora- 

 tion, says Sea Grant Director Ron Hodson. 

 He emphasizes that the work is just 

 beginning. 



"With the interest of federal 

 agencies and state agencies, I'm very 

 optimistic that funds will be made 

 available to continue that research," 

 Hodson says. □ 



Shellfish 



The price for these outbreaks in 

 terms of lost seafood sales can be 

 steep. In 1988, New York state 

 suffered a $2 million loss from 

 reduced scallop landings caused by 

 brown tide. 



Besides starving shellfish, brown 

 tide damages habitat by darkening 

 the water and diminishing the light 

 needed by bottom-dwelling eelgrass, 

 a nursery and refuge for many fish 

 species. The algae also interrupts the 

 food web at about 500,000 cells per 

 milliliter by decreasing protozoa, a 

 key nutritional link between phy- 

 toplankton and their predators, such 

 as some juvenile fish. With less food 

 available, juvenile fish may grow more 

 slowly or die. □ —J.F.N. 



Br 



Brown Tide - Deadly to 



)rown tide is a destructive 

 algal bloom that can starve shellfish, 

 damage critical nursery habitat and 

 interrupt the marine food web. 



Its blooms are caused by a 

 bacteria-sized algae, Aureococcus 

 cwophagefferens, during the late 

 spring and summer in coastal 

 embayments from Narragansett 

 Bay, R.I., to Barnegat Bay, N.J., says 

 Darcy Lonsdale, a New York Sea 

 Grant researcher. Different brown 

 tide species are found in the Gulf of 

 Mexico. 



"There is no reason to suspect 

 that this alga is directly harmful to 

 humans," Lonsdale says. "But we 

 are concerned because it is appar- 

 ently quite harmful to organisms 



that consume phytoplankton." 



Brown tide can starve shellfish — 

 especially mussels, scallops and hard 

 clams — by reducing their feeding 

 response. Juvenile hard clams tend to 

 grow slower during brown tides, and 

 scallops seem to stop feeding when 

 concentrations reach 250,000 cells per 

 milliliter of seawater (a milliliter equals 

 about 20 drops) — the point at which 

 researchers begin to see negative effects. 

 At times, brown tide blooms reach 

 concentrations of more than 1 million 

 cells per milliliter. 



"When shellfish are out in the bay 

 and they start to experience higher and 

 higher concentrations of brown tide, they 

 stop feeding, close up and starve," 

 Lonsdale says. 



COASTWATCH 19 



