Environmental+Toxicology+Tox+2000+notes (2)

As with all phases of ecological risk assessment the

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Unformatted text preview: ly, populations of the Double -Crested Cormorants have shown a remarkable recovery, despite the incidence of crossed -bill and other developmental abnormalities. The loss of population growth that results from this response is clearly not pertinent when assessed in the context of ecological relevance. Recoveries similar to those of the Double -crested Cormorants have been seen in other bird species around the Great Lakes. Bald Eagle ( Haliaeetus leucocephalus) populations around the Great Lakes have increased since 1980, partially throu gh recruitment from inland populations but also through successful rearing of young. In this species, the absolute number of bill deformities has increased from 1960 (2) to 1990 (7). However, this increased incidence must be assessed against the reported increased population, increased egg production, and increased chick survival. Increases in populations of Herring gull ( Larus argentatus) and osprey have also been reported in the Great Lakes, although the increase in the latter is judged to be more as a result of increased availability of artificial nesting sites. Caspian terns, on the other hand, have not shown as large rates of recovery as other water -birds in the Great Lakes. Populations in Caspian tern colonies close to the US shores of the Great L akes are only showing growth because of recruitment of individuals from Canadian colonies. This is due, in part, to the location of US colonies near to areas of greater contamination and the long reproductive cycle (7 years) of this bird. 3.3.5.3 NON-PERSISTENT ENDOCRINE MODULATING SUBSTANCE S Through a better understanding of the interactions between persistence, lipid solubility and movements of substances through food chains, nat ional and international regulations have responded with controls and these have resulted in observable improvements. In parallel to regulation, these improvements have occurred first in those regions where regulations were first enforced. There is still much to be done in other regions, particularly in internationally regulated areas such as the open oceans where concerted action is more slowly achieved. Endocrine modulating responses from non -persistent substances have not been as well documented as those from the persistent organic pollutants. Because of their lack of persistence, these substances present a special case with respect to endocrine modulation as consideration of the probability of exposure and sensitivity becomes more important. Endocrine modulation has recently been observed in fish exposed to pulp mills effluents. Until installation of treatment facilities, effects on fish in pulp mill receiving waters were acute and lethal. Large concentrations of resin acids, highly chlorinated phen ols, and biological oxygen demand acted in concert to reduce fish populations to small numbers in receiving waters with small to moderate dilutions (Owens 1991). With appropriate treatment of effluents, toxicity has been reduced to below the threshold of acute and chronic lethality. Under these conditions, fish have re...
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This document was uploaded on 04/07/2014.

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