We assessed relationships between environmental characteristics and macroinvertebrate assemblages in lotic habitats of California's Central Valley with community metric and multivariate statistical approaches. Using canonical ordination analyses, we contrasted results when assemblage structure was assessed with macroinvertebrate metrics, as suggested for use in indices of biotic integrity, or with genera abundances. Our objectives were to identify metrics or taxa diagnostic of lotic environmental stressors and compare the capacity of these approaches to detect stressors in order to suggest how they might be used to diagnose stressors. For macroinvertebrate metrics, redundancy analysis (RDA) extracted three axes correlated with channel morphology and substrates. For genera abundances, canonical correspondence analysis (CCA) extracted two axes correlated with soluble salts and with channel morphology and substrates but did not separate these gradients onto different axes. Cluster analyses identified five RDA and five CCA site groups, which exhibited differences for environmental variables, metrics, or genera abundances, and agreement between the analyses in partitioning of sites was greater than if sites were partitioned randomly. These approaches differ in their ability to detect environmental stressors, because they measure different aspects of assemblages and would be complementary in design of new metrics diagnostic of stressors.
Bibliographical noteFunding Information:
Field sampling design and data collection were funded by USEPA’s Office of Research and Development as part of its Regional Environmental Monitoring and Assessment Programs. Field work and sorting and identifications of macroinver-tebrate samples were conducted by personnel of the California Department of Fish and Game supervised by M. Peterson-Dunne and J. Harrington. Both provided details on the sampling and analyses for macroinvertebrates and water chemistry. Comments by S. V. Fend (USGS, WRD, Menlo Park, CA), V. H. Resh (University of California at Berkeley), A. T. Herlihy (Oregon State University), K. Wehrly and F. A. Fulk (USEPA, NERL, Cincinnati, OH), and several anonymous reviewers greatly improved the quality of the manuscript. The data analyses and preparation of this manuscript were supported in part by appointment of the first author to the Postgraduate Research Program at the National Exposure Research Laboratory administered by the Oak Ridge Institute for Science and Education through an interagency agreement between the U.S. Department of Energy and the U.S. Environmental Protection Agency.
- Biotic indices
- Canonical analyses
- Central Valley Ecoregion
- Macroinvertebrate assemblages