Meiobenthic arthropod communities in new streams in Glacier Bay National Park, Alaska

Meiobenthic arthropod community structure (comprising species of chydorid and macrothricid Cladocera, cyclopoid and harpacticoid Copepoda, Ostracoda and Hydrachnida) was examined along a chronosequence of five streams of different ages (20-150 years) in Glacier Bay National Park to determine whether meiobenthic arthropod colonisation had occurred and successional patterns were evident. Meiobenthic arthropod communities were found in all five streams, indicating that initial colonisation was rapid, and there was clear evidence of successional patterns at both the species and the community level. Meiobenthic arthropod species richness and density rose along the chronosequence and was correlated with increasing stream age and CPOM and increasing channel stability as measured by Pfankuch's Index. These trends were largely driven by the Ostracoda and harpacticoid copepods. The latter group also exhibited a distinct shift in species composition with increasing stream age. Initial meiobenthic arthropod colonisation may be facilitated by the large breeding colonies of Canada geese that occur on the wetlands associated with newly deglaciated areas of Glacier Bay. Processes driving meiobenthic arthropod community succession in newly deglaciated streams are likely to be complex and may involve water temperature, channel stability, riparian zone development and CPOM/woody debris influx to the stream. Rapid meiobenthic arthropod colonisation and subsequent succession may have important implications for fish colonisation, and subsequent establishment in new streams as meiobenthic arthropods are important food items for juvenile fish.