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

For example the public is very concerned about

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Unformatted text preview: y relevance. For example, the public is very concerned about declines in Af rican elephants and peregrine falcons. Declines (or increases) in African elephant populations have a major impact on the ecology of the savannah, however, the near -extinction of the peregrine falcon in large parts of N. America had no apparent effects on the ecosystem. This suggests that we should seek endpoints that have high ecological as well as societal relevance. This may require that we educate the public on the value of the biologically relevant assessment endpoints. Assessment endpoints must al so be unambiguous and must not be confused with policy goals. Thus trite statements such as ―protection of indigenous populations‖ or ―ecosystem health‖ have no place in the science of ecotoxicology, however, they may be very laudable political or cultural objectives. These goals are usually not measurable and therefore, progress and achievement towards targets cannot be gauged. Effect Measures Are responses that are (or may be) more easily quantified than assessment endpoints but are, however, related quantitatively or qualitatively to the assessment endpoint. They are always expressed as concentrations or doses. Measures of effect should be directly related to biologically significant responses. For example, a physiological or biochemical change in an organism (often referred to as an indicator or bioindicator) must be related to the survival or fecundity of the population before it can become a useful measurement of effect. One of the most common measures of effect used in ecotoxicology is mortality of organisms exposed to the stressor. Effect measures normally have units related to exposure, i.e., concentratio n, for a toxic substance in a matrix such as water. ● Test endpoints are the responses that are observed in a bioassay or toxicity test. For acute tests, in many organisms, mortality is the usual test endpoint. For small mobile organisms, movement or la ck of movement is a test endpoint. Illustration s of these are given in Section 3.2. 3.1.2 Assessing effects in ecosystem s Ecosystems consist of a number of interacting populations of organisms that co -exist in a somewhat stable or predictable manner. One of the measures used to characterize the ecosystem is the range and variety of species that it contains (a taxonomic or di versity-oriented assessment) another way to would be to characterize ecosystem functions, such as productivity, photosynthesis, nutrient cycling, community respiration, etc. The system of characterization Function chosen depends on the expertise of the observer and, to some extent, on Original ecosystem the focus that one wishes to before impact concentrate on. Application of taxonomic measures to assess change Restored ecosystem in ecosystems is essentially the with less range than the imposition of human values on the original and displaced Structure ecosystem. Humans classify with respect to function and diversity organisms into species but the ecosystem ― classifies‖ by function, since it cannot ―recognize‖ a spec...
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