An inter-catchment assessment of macroinvertebrate communities across groundwater-fed streams within Denali National Park, interior Alaska

Groundwater-fed streams are typically hotspots of aquatic biodiversity within glacierized catchments. Surface water physicochemistry and macroinvertebrate communities within five groundwater-fed streams were characterised across catchments in Denali National Park, interior Alaska. The main aim of this study was to assess whether hydrological controls on macroinvertebrate communities (e.g. flow permanence) identified within previous catchment-specific studies are present at wider spatial scales, across multiple groundwater-fed streams located on alluvial terraces within glacierized catchments. Macroinvertebrate community diversity, in general, was shown to be high and relatively invariant across the groundwater-fed streams assessed. Flow permanence was shown to be responsible for the greatest differences in macroinvertebrate communities. Although ephemeral and perennial streams exhibited no differences in diversity, perennial streams maintained higher total abundance and taxonomic richness of macroinvertebrates than ephemeral streams. Furthermore, macroinvertebrate community structure was also shown to be different, with ephemeral streams composed of a smaller number of specialised taxa able to withstand disturbance from periodic dewatering. Relationships between physicochemical variables and macroinvertebrate diversity, however were not observed across the catchments. The high diversity and structural heterogeneity of macroinvertebrate communities observed across alluvial terrace streams indicated the importance of these systems as biodiversity hotspots in regions under threat from climate change.