tailieunhanh - Ebook Ecotoxicology – A comprehensive treatment: Part 2

(BQ) Part 2 book “Ecotoxicology – A comprehensive treatment” has contents: Disturbance ecology and the responses of communities to contaminants, community responses to global and atmospheric stressors, effects of contaminants on trophic structure and food webs, effects of contaminants on trophic structure and food webs, and other contents. | of 24 Application Multimetric and Multivariate Approaches in Community Ecotoxicology The most distinct and beautiful statement of any truth must take at last the mathematical form. (Henry David Thoreau, in Walls 1999) INTRODUCTION Methods to assess the effects of contaminants and other anthropogenic stressors on communities range from computationally simple indices such as species richness to complex, computer-dependent algorithms such as multivariate analyses. The simplest community indices use species presence/absence or abundance data to show how individuals in the community are distributed among species. The advantages of these indices are their intuitive meaning and their ability to reduce complex data to a single number. Only slightly more involved but retaining more information, species abundance curves described in Chapter 22 characterize the distribution of individuals among the species by fitting abundance data to specified distributions. Estimated distributional parameters from species abundance models provide a parsimonious description of the community. Slightly more involved composite measures require additional knowledge about community qualities (., the trophic status of a species) to produce indices developed specifically to gauge diminished community integrity due to anthropogenic stressors. Currently, the most popular of these composite indices is Karr’s (1981) index of biological integrity (IBI). These composite indices require more ecological knowledge of the community than measures of species richness or species abundance models but have the advantage of being focused primarily on human effects on communities or species assemblages. More convenient, but perhaps applying less ecology than warranted, distributions of individual species effect metrics (., distributions of 96-h LC50 values) are used to predict “safe concentrations” that presumably protect all but a specified, low percentage of the species making up the community. Even