pollutants in the water column; (3) current systems in the Bay prevent loss of 

 pollutants to main Atlantic waters; (4) colder waters there slow bacterial 

 degradation of the contaminants. 



In some cases pollutant level analyses show trends related to age and sex of 

 the animals. Harbor porpoises from the Bay of Fundy exhibit a marked increase 

 in DDT level with age in males but a definite decrease with age in females 

 (Gaskin et al. 1976). Presumably, the female transfers residual 

 organochlorines to her fetus via the placenta. No documentation exists on 

 effects of these pollutants on developing fetuses and young animals. A 

 similar study of harbor seals from the Gulf of Maine and the Bay of Fundy 

 reveals that lactating females had significantly lower pollutant levels than 

 all other seals tested (Gaskin et al. 1973). 



A review of current trends and research results shows evidence of a definite 

 decrease in organochlorine levels in Bay of Fundy harbor porpoises since 1969. 

 The decrease is exhibited by both males and females regardless of age, 

 although males still retain higher levels overall (Gaskin et al. 1976). It is 

 hoped that continued restriction on the production and use of organochlorines 

 will further reduce their presence in marine organisms in the Bay of Fundy and 

 coastal Maine. 



Heavy metals . These metals, particularly mercury, are increasingly 

 conspicuous in marine systems (see chapter 3, "Human Impacts on the 

 Ecosystem"). Analyses of marine mammal tissue taken from the wild (by capture 

 or stranding) indicate exceedingly high mercury concentrations may be present 

 in certain populations. Katona and coworkers (1977) summarizes study results 

 on heavy metal contamination in marine mammals known to inhabit the Gulf of 

 Maine (table 13-8). 



Both mercury and cadmium concentrations in marine mammals appear to be 

 positively correlated with age. Again, the relatively high trophic position 

 in the aquatic food chain and long life span of most of these animals 

 contribute to the high level of accumulation of heavy metals. Some 

 researchers propose that harp seals have lower mercury contamination than gray 

 seals or harbor seals because harp seals feed on a lower trophic level, that 

 is, capelin and crustaceans vs. the cod and flatfish on which the harbor and 

 gray seals feed (Katona et al. 1977). Related research indicates that 

 contaminant levels of cadmium, zinc and copper in harbor seals from the German 

 North sea are much higher than prey fish values. Mercury concentrations in 

 seals were more than 1000 times greater than corresponding prey fish values. 



The major storage depositories for heavy metals in marine mammals are the 

 liver and the brain. This pattern of mercury distribution is unique, unlike 

 that of other animals tested. In people, for example, most mercury is present 

 as methlymercury , which is rapidly transported throughout the body. In fish, 

 the staple food of most marine mammals, almost all mercury is in the 

 methylmercury form (Katona et al. 1977). However, in seals, harbor porpoises, 

 and pilot whales, it has been confirmed that mercury is concentrated in the 

 liver in a de-methylated form. This storage of the de-methylated mercury in 

 the liver, with minimal transport to other body tissues, may be the factor 

 that enables seals to maintain high contaminant levels without exhibiting 

 normal mercuric poisoning effects. Current research suggests that there is a 

 saturation limit and older seals may surpass that level and begin to pass 



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