Physiological and Histological Indicators

Physiological and behavioral indicators of impact within a population are the classical means by which the health of populations are assessed. The major drawback has been the extrapolation of these factors based upon the health of an individual organism, attributing the damage to a particular pollutant and extrapolating this to the population level. 

As described in earlier chapters, toxicants can cause a great deal of apparent damage which can be observed at the organismal level. Animals often 

Perhaps most promising in a clinical sense is the ability to detect enzymes present in the blood plasma due to the damage and subsequent lesion of organs. Several enzymes such as the LDHs are specific as to tissue. The presence of an enzyme not normally associated with the blood plasma can provide specific evidence of the organ system damaged and, perhaps, an understanding of the toxicant. 

Molecular and physiological indicators do offer specific advantages in monitoring an environment for toxicant stressors. Many enzymes are 

Currently, it is not possible to accurately transform data gathered from molecular markers to predict effects at the population and community levels of organization. Certainly, behavioral alterations caused by acetylcholinesterase inhibitors may cause an increase in predation or increase the tendency of a parent to abandon a brood, but the long-term populational effects are difficult to estimate. In the estimation and classification of potential effects, it may be the pattern of indicators that is more important than the simple occurrence of one that is important. 

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