The researchers found that in most 

 cases, the two groups of crabbers and 

 the community controls reported similar 

 levels of illness and injury. However, 

 both groups of crabbers reported higher 

 — and nearly identical — incidences of 

 skin disorders than the community 

 controls. The researchers 

 concluded that skin disorders are 

 a common occupational hazard 

 among crabbers and cannot be 

 attributed to Pfiesteria or similar 

 dinoflagellates. 



Increased exposure to water 

 (as measured by the number of 

 traps the crabbers pull per day) 

 did not result in increased 

 incidence of illness. And there 

 was no statistical difference in 

 levels of illness between those 

 who worked in areas with fish 

 kills and those who worked in 

 areas with few or no kills. The 

 two areas known to have had fish 

 kills — the Neuse River and the 

 Pamlico and Pungo rivers — did 

 have lower well-to-ill ratios than 

 areas less prone to kills. This 

 finding may be some cause for 

 concern about the human-health 

 impacts in these areas as opposed 

 to others, the researchers reported. 



Naming 

 mnairnTent 

 n Kats 



In another study, Duke 

 University scientist Ed Levin found that 

 rats injected with Pfiesteria display a 

 significant learning deficit when called 

 on to attempt new tasks as long as 10 

 weeks later. Levin's work was published 

 in the December issue of Environmental 

 Health Perspectives, the journal of the 

 National Institute of Environmental 

 Health Sciences. 



"It seemed to be relatively specific 

 in that the rats seemed to be otherwise 

 healthy and their appearance seemed 

 normal," Levin says. 



In addition to appearing physically 

 well, the rats showed no Pfiesteria- 



induced effects in blood count or in a 

 standard pathological screening of brain, 

 liver, lungs, kidneys and spleen. 



Water samples were taken from 

 aquariums in which Pfiesteria were 

 killing fish. The samples were frozen, 

 thawed and injected into rats. The 



Griffith estimated each crabber's exposure to the water 

 by the number of pots he or she worked. 



significant learning impairments were 

 documented in rats required to learn a 

 new task after they received recently 

 frozen injections of Pfiesteria. However, 

 no effect was seen in the recall of previ- 

 ously learned tasks. These tests were not 

 carried out beyond 10 weeks. 



The persistent learning impairment 

 in rats might be comparable to the 

 cognitive deficits humans have shown 

 after exposure to Pfiesteria in the lab, 

 the researchers concluded. The findings 

 were replicated in several studies, but 

 more are needed to determine which 

 chemical causes the effects, Levin says. 



"We're going through different 

 extracts to see which (chemical) is the 

 bad actor," Levin says. "We're using 

 procedures to help identify the critical 

 toxin, the critical chemical in Pfiesteria." 



From that information, researchers 

 can help determine what exposure levels 

 warrant concern and develop 

 therapeutic treatments for the 

 learning deficits. 



Environmental 

 Causes 



At the UNC Institute of 

 Marine Sciences, researchers Hans 

 Paerl and James Pinckney 

 examined whether nutrients spur 

 growth of the dominant nontoxic 

 zoospore stage of Pfiesteria and 

 whether nutrient-induced increases 

 in phytoplankton — a primary 

 food source for Pfiesteria — 

 boosted the dinoflagellate's 

 numbers. 



They concluded that 

 Pfiesteria does not respond 

 strongly to the addition of nitrogen 

 and phosphorus — nutrients that 

 commonly reach state waterways 

 through runoff and discharge 

 pipes. But phytoplankton do 

 respond to nitrogen, and increases 

 in phytoplankton appear to direct 

 changes in Pfiesteria-Wke 

 zoospores. Thus, it appears that 

 phytoplankton are the nutrition 

 source that supports the growth of 

 Pfiesteria-Wke zoospores. 



"We saw the prey organisms 

 increase, but we didn't see Pfiesteria 

 increase at the same time," Paerl says. 

 "That says that a slug of nutrients that 

 enters the river probably doesn't have an 

 immediate short-term stimulator effect on 

 Pfiesteria, but in the long term you can 

 see a pattern." 



Their experiments used water from a 

 location on the Neuse River where both 

 Pfiesteria and fish kills have been 

 reported. The water was transferred to 

 mesocosms — translucent fiberglass 

 tanks. The scientists then simulated 



18 HIGH SEASON 1998 



