SPATIAL AND SEASONAL ASSOCIATIONS OF BENTHIC MACROINVERTEBRATES AND DETRITUS IN AN ALASKAN SUBARCTIC STREAM

Seasonal and spatial patterns of benthic invertebrate abundance were examined in relation to benthic detritus in Monument Creek, an Alaskan subarctic stream. The total macroinvertebrate fauna showed a mid-summer low in abundance, increasing to seasonal highs in winter/early spring (Nov./May). Shredders were a small portion of the benthic fauna or leaf pack fauna in summer but increased rapidly (in biovolume) following autumnal leaf fall to dominate the fauna by early winter (Oct./Nov.). Abundance was strongly correlated with quantity of detritus in the sample. Comparison of benthic macroinvertebrate densities from Alaskan streams with comparable data from temperate zone streams shows that Alaskan streams are similar to temperate zone streams in range of abundance. Each unit of benthic detritus in Monument Creek is associated with a relatively large number of small (low individual biomass) shredders compared to streams in temperate regions. Detrital resources in this subarctic stream were meager, compared to temperate streams, and appeared to strongly influence the spatial and temporal patterns of detritivores.