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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.
18.104.22.168 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
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This document was uploaded on 04/07/2014.
- Fall '14
- The Land