Elevational and seasonal differences in macroinvertebrate community structure in alpine streams

Context Changes in temperature regimes can alter stream macroinvertebrate community structure. We hypothesised that benthic community structure in alpine streams responded to spatial-temporal changes in environmental factors and thermal regimes. Aims We aimed to evaluate the relationship between macroinvertebrate community structure and water-quality parameters including temperature, and the influence of sampling sites positioned above or below the tree line. Methods Continuously measured water temperatures, in situ measurements of other variables and macroinvertebrates were sampled seasonally across an elevation gradient in an Australian alpine region. Key results Sites above the tree line had the greatest annual range in water temperature compared with sites below the tree line. PERMANOVA showed highly significant differences in the macroinvertebrate community structure among sites at different elevations. Redundancy analysis showed that degree-days and total nitrogen concentrations had a strong influence on macroinvertebrate distribution at sites below the tree line. We observed fewer families, number of Ephemeroptera, Plecoptera and Trichoptera (EPT) individuals and a lower EPT family richness at the two highest sites, than at sites below the tree line. Conclusions Although other variables may be influential, the larger annual temperature range at the two sites sampled above the tree line is stressful to stream macroinvertebrates and this should be considered in relation to risks from climate change. Implications Increase in water temperature due to climate change will likely affect the biology of organisms from foraging, reproduction, growth and development to finding suitable habitats.