Ebook Ecotoxicology – A comprehensive treatment: Part 2
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Ebook Ecotoxicology – A comprehensive treatment: Part 2
24 Application of Multimetric and Multivariate Approaches in Community EcotoxicologyThe most distinct and beautiful statement of any truth must take a Ebook Ecotoxicology – A comprehensive treatment: Part 2at last the mathematical form.(Henry David Thoreau, in Walls 1999124.1 INTRODUCTIONMethods 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 multi Ebook Ecotoxicology – A comprehensive treatment: Part 2variate analyses. The simplest community indices use Species pres-ence/absence or abundance data to show how individuals in the community are distribuEbook Ecotoxicology – A comprehensive treatment: Part 2
ted among species. The advantages of these indices are their intuitive meaning and their ability to reduce complex data to a single number. Only sligh24 Application of Multimetric and Multivariate Approaches in Community EcotoxicologyThe most distinct and beautiful statement of any truth must take a Ebook Ecotoxicology – A comprehensive treatment: Part 2the Species by titling 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 (e.g.. the trophic Ebook Ecotoxicology – A comprehensive treatment: Part 2 status of a species) to produce indices developed specifically to gauge diminished community integrity due to anthropogenic stressors. Currently, theEbook Ecotoxicology – A comprehensive treatment: Part 2
most popular of these composite indices is Karr's (1981) index of biological integrity (IB1). These composite indices require more ecological knowled24 Application of Multimetric and Multivariate Approaches in Community EcotoxicologyThe most distinct and beautiful statement of any truth must take a Ebook Ecotoxicology – A comprehensive treatment: Part 2n communities or species assemblages. More convenient, but perhaps applying less ecology than warranted, distributions of individual species effect metrics (e.g.. distributions of 96-h LC50 values) are used to predict “safe concentrations" that presumably protect all but a specified, low percentage Ebook Ecotoxicology – A comprehensive treatment: Part 2of the species making up the community. Even more computationally intense methods, such as multivariate analyses, aim to reduce the number of data dimEbook Ecotoxicology – A comprehensive treatment: Part 2
ensions to an interpretable low number, and to quantify similarities or differences among sampling units. These last methods tend to generate interpre24 Application of Multimetric and Multivariate Approaches in Community EcotoxicologyThe most distinct and beautiful statement of any truth must take a Ebook Ecotoxicology – A comprehensive treatment: Part 2during their application. However, (he value of these methods in identifying clear explanations from complex data sets makes worthwhile any effort spent wading through obtuse computer manuals or dealing with the associated jargon.Jargon, not argument, is your best ally in keeping him from the Church Ebook Ecotoxicology – A comprehensive treatment: Part 2.(Lewis 1942)473474Ecotoxicology: A Comprehensive Treatment24.1.1Comparison of Multimetric and MultivariateApproachesMultimetric and multivariate apprEbook Ecotoxicology – A comprehensive treatment: Part 2
oaches are applied to community data with the intent of rendering the associated complex array of information to a more parsimonious form. Because eco24 Application of Multimetric and Multivariate Approaches in Community EcotoxicologyThe most distinct and beautiful statement of any truth must take a Ebook Ecotoxicology – A comprehensive treatment: Part 2are often necessary to examine the complex relationships between species assemblages and multiple environmental factors. Multivariate approaches reduce complex, multidimensional data to two or three dimensions, thus allowing researchers to identify key environmental variables responsible for pattern Ebook Ecotoxicology – A comprehensive treatment: Part 2s of species abundance. In contrast, muhimetric indices integrate a diverse suite of measures, often across several levels of biological organization,Ebook Ecotoxicology – A comprehensive treatment: Part 2
to assess biological integrity. It is appropriate to consider these two approaches together because the community data necessary to calculate a multi24 Application of Multimetric and Multivariate Approaches in Community EcotoxicologyThe most distinct and beautiful statement of any truth must take a Ebook Ecotoxicology – A comprehensive treatment: Part 2nd multimetric approaches. Reynoldson et al. (1997) concluded that multivariate approaches provided greater accuracy and precision for assessing reference conditions in streams. Terlizzi el al. (2005) showed that univariate measures of molluscan community structure (species richness) showed little r Ebook Ecotoxicology – A comprehensive treatment: Part 2esponse to contamination whereas multivariate analyses identified significant differences between reference and polluted sites. Thomas and Hall (2006)Ebook Ecotoxicology – A comprehensive treatment: Part 2
compared the ability of individual metrics, multivariate approaches, and multimetric indices to identify impairment in periphyton, macroinvertebrate,24 Application of Multimetric and Multivariate Approaches in Community EcotoxicologyThe most distinct and beautiful statement of any truth must take a Ebook Ecotoxicology – A comprehensive treatment: Part 2or identifying spatial and temporal differences in each community. In a comprehensive analysis of community indices and multivariate approaches. Kilgour et al. (2004) compared the relative sensit-i\ ity of seven benthic community metrics and three multivariate indices to contamination associated wit Ebook Ecotoxicology – A comprehensive treatment: Part 2h mines, pulp and paper mills, and urbanization. Multivariate approaches identified significant differences associated with each of the perturbationsEbook Ecotoxicology – A comprehensive treatment: Part 2
and greater effect sizes compared to the community metrics. Although the examples described above seem to highlight the greater discriminatory ability24 Application of Multimetric and Multivariate Approaches in Community EcotoxicologyThe most distinct and beautiful statement of any truth must take a Ebook Ecotoxicology – A comprehensive treatment: Part 2 likely vary with the spatial scale of an investigation (Quintino et al. 2006). Despite their grow ing popularity in Canada and Europe, multivariate approaches have received considerably less attention in the United States (Resh et al. 1995). Multivariate analyses have been criticized because of the Ebook Ecotoxicology – A comprehensive treatment: Part 2ir inherent statistical complexity and because results are often difficult to interpret (Fore et al. 1996. Gerritsen 1995). The complex graphical reprEbook Ecotoxicology – A comprehensive treatment: Part 2
esentations of multivariate results are often of limited value to non-ecologists and managers. Although strict reliance on complex statistical algorit24 Application of Multimetric and Multivariate Approaches in Community EcotoxicologyThe most distinct and beautiful statement of any truth must take a Ebook Ecotoxicology – A comprehensive treatment: Part 2r quality. Because community-environment relationships are inherently multidimensional, approaches such as multivariate analyses that consider interactions among predictor variables and their effects on multiple response variables are necessary. New approaches, such as the application of principal r Ebook Ecotoxicology – A comprehensive treatment: Part 2esponse curves (Pardal el al. 2004). quantify multivariate community responses to contaminants in ways that are more accessible to managers and policyEbook Ecotoxicology – A comprehensive treatment: Part 2
makers. We agree with the recommendations of Reynoldson et al. (1997) that multivariate and multimetric approaches are complementary and should be use24 Application of Multimetric and Multivariate Approaches in Community EcotoxicologyThe most distinct and beautiful statement of any truth must take a Ebook Ecotoxicology – A comprehensive treatment: Part 2ensitive groups, or other measures typically included in a multimetric index. Griffith et al. (2003) used this approach in their evaluation of the relationship between macroinvertebrate assemblages and environmental gradients. Multivariate statistical analysis (redundancy analysis) using metrics der Ebook Ecotoxicology – A comprehensive treatment: Part 2ived from an index of biotic integrity provided complementary results to canonical correspondence analysis based on macroinvertebrate abundance. AlterEbook Ecotoxicology – A comprehensive treatment: Part 2
natively.Application of Multimetric and Multivariate Approaches in Community Ecotoxicology475a mullirneiric index similar to Karr's 1B1 could be devel24 Application of Multimetric and Multivariate Approaches in Community EcotoxicologyThe most distinct and beautiful statement of any truth must take a Ebook Ecotoxicology – A comprehensive treatment: Part 2multivariate procedures identify variables that arc most important for separation of groups (generally locations, sampling stations). Variables shown to be responsible for separation of reference and impacted stations could be combined in a mullimclric index. Integration of multivariate and mullimcl Ebook Ecotoxicology – A comprehensive treatment: Part 2ric approaches may be necessary to delect perturbations when relatively weak relationships between stressors and community structure exist (Chenery anEbook Ecotoxicology – A comprehensive treatment: Part 2
d Mudge 2005). Finally, we note that our enthusiasm for multimetric and multivariate approaches in communitylevel bioassessment is not shared by all r24 Application of Multimetric and Multivariate Approaches in Community EcotoxicologyThe most distinct and beautiful statement of any truth must take a Ebook Ecotoxicology – A comprehensive treatment: Part 2. These researchers advocate an alternative approach in which effects of stressors on individual taxa with known species-level tolerances are employed to develop an overall assessment of community-level impact.24.2 MULTIMETRIC INDICESA principal objective of the 1972 Federal Water Pollution Control Ebook Ecotoxicology – A comprehensive treatment: Part 2Act and its 1977 and 1987 amendments is to restore and maintain the biological integrity of the nation s waters.(Miller et al. 19881One of the most siEbook Ecotoxicology – A comprehensive treatment: Part 2
gnificant advances in the field of biological assessments over the past 20 years was the development and application of inultimetric approaches for meGọi ngay
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