Importance of behaviour to the re-establishment of drifting Ephemeroptera

Experiments with mayfly larvae in a laboratory stream revealed significant differences among settling capabilities of four species. Quantitative measures of overall settling capacity, contribution of morphology and that of behaviour were derived for comparative purposes. Importance of behaviour to re-establishment was greater in species which frequently show die1 drift periodicities than those which do not. Although morphological differences between species were large, mean size of nymphs was more important in determining rates of return of dead animals. Intraspecific vari-ations in the ability of drifting individuals to become re-estab-1ished may partially account for changes in the relative distri-bution of populations over time

Functional Changes in Littoral Macroinvertebrate Communities in Response to Watershed-Level Anthropogenic Stress

Watershed-scale anthropogenic stressors have profound effects on aquatic communities. Although several functional traits of stream macroinvertebrates change predictably in response to land development and urbanization, little is known about macroinvertebrate functional responses in lakes. We assessed functional community structure, functional diversity (Rao’s quadratic entropy) and voltinism in macroinvertebrate communities sampled across the full gradient of anthropogenic stress in Laurentian Great Lakes coastal wetlands. Functional diversity and voltinism significantly decreased with increasing development, whereas agriculture had smaller or non-significant effects. Functional community structure was affected by watershed-scale development, as demonstrated by an ordination analysis followed by regression. Because functional community structure affects energy flow and ecosystem function, and functional diversity is known to have important implications for ecosystem resilience to further environmental change, these results highlight the necessity of finding ways to remediate or at least ameliorate these effects