Macroinverfebrate Abundance and Production of Psammophifous Chironomidae in Shifting Sand Areas of a Lowland River

Abstract

Abundance and biomass of benthic macroinvertebrates from shifting sand areas in the bed of the Sand River in central Alberta, Canada, were examined for 1 yr. Macroinvertebrate density ranged from 12 000 to 78 000 individuals/m2, but total biomass was low (50–490 mg/m2 dry mass) due to the small size of most organisms. The interstitial larvae of two chironomid species (Robackia demeijerei and Rheosmittia sp.) contributed a mean of 80.6% biomass and 92.8% of total number of macroinvertebrates. Total annual secondary production of these two species (752.0 ± 144.5 mg∙m−2∙yr−1) was used as an estimate of total secondary production of benthic macroinvertebrates in shifting sand areas. Both R. demeijerei and Rheosmittia sp. exhibited larval growth and development rates much slower than those reported for comparably sized species in other habitats. Food or frequent disturbance may limit the growth of these species. Although unit area biomass and production were low relative to other lotie habitats, shifting sand areas make significant contributions to the river ecosystem because they occupy a large proportion of the river bed.