Concordance of diatom, macroinvertebrate and fish assemblages in streams at nested spatial scales: Implications for ecological integrity

Understanding the concordance among different assemblages as well as their responses to the environmental gradients at multiple spatial scales is an important issue in conservation biology and in the assessment of ecological integrity. We examined the community concordance among diatoms, macroinvertebrates and fish in minimally disturbed streams on four nested spatial scales (i.e., national, catchment, sub-catchment and mountain or lowland at sub-catchment scales) in Korea. The results, based on non-metric multidimensional scaling, showed that diatoms, macroinvertebrates and fish displayed consistent patterns that were strongly structured along an altitude gradient at the national scale. However, the responses to all other influential environmental factors differed by assemblages. The community composition of fish closely reflected the gradients of larger scale environmental factors (i.e., geographical and hydrological variables), whereas macroinvertebrates mainly reflected the changes at relatively finer environmental scales (e.g., hydrological variables and substrate composition). Diatoms showed relatively weak relationships with environmental variables except for the altitudinal gradient. Community concordance based on Protest was significant at four nested spatial scales, although most cases of community concordances were relatively weak. Fish and macroinvertebrates showed high concordance at the national and catchment scales, whereas macroinvertebrates and diatoms showed high concordance at smaller scales (i.e., mountain or lowland at sub-catchment). Finally, our study demonstrated that community concordance among diatoms, macroinvertebrates and fish would be different according to spatial scales and even in the same scales and that use of a representative taxon to assess ecological integrity should be applied with caution.