BENTHIC MACROINVERTEBRATE RESPONSE TO HABITAT RESTORATION IN A CONSTRUCTED ARCTIC STREAM

We examined the ability of engineered rock structures to enhance the productive capacity of benthic macroinvertebrates 2years after their installation in a constructed stream in the Northwest Territories, Canada. We used a control-impact design to compare biological attributes of the structures to those of riffles in natural reference streams and among individual structures. The biomass of epilithon and coarse particulate organic matter, cover by bryophytes and macrophytes and volume of woody debris, however, were similar at structures and unenhanced control sites in the constructed stream and lower than at riffles in reference streams. Total macroinvertebrate density and densities of Chironomidae, Nematoda and Oligochaeta did not differ among engineered structures, unenhanced sites and reference riffles. In contrast, reference streams supported higher densities of Simuliidae and Ephemeroptera compared with engineered structures and unenhanced sites within the channel. Total biomass, biomass of Chironomidae, non-chironomid Diptera and combined biomasses of (i) Nematoda, Oligochaeta and Turbellaria and (ii) Ephemeroptera, Plecoptera and Hemiptera from reference riffles exceeded those at engineered structures. Density and biomass of macroinvertebrates varied within and among structure types and were highest at one of two ramps, one of two vanes and at the single groin compared with other structures. In the majority of cases, density and biomass of macroinvertebrates from individual structures were less than those at reference streams. These results suggest that engineered structures had variable effects on the productive capacity of benthic macroinvertebrates of the constructed streams and may be related to the extent that structures provided habitat conditions characteristic of reference riffles. (c) Her Majesty the Queen in Right of Canada 2011. Reproduced with the permission of the Minister of Natural Resources.