Importance of detritus, substrate and flow to macroinvertebrate distribution in sections of the West River

The importance of near-bed flow and other types of environmental variables to macroinvertebrate distribution was examined within sections of a stream in Prince Edward Island. To carry out this part of the study, different methods of measuring near-bed flow were tested. The methods were tested at 5 sites on 3 streams, to choose the most practical and reliable methods for evaluating shear velocity and roughness to compare near-bed flow among patches where macroinvertebrates were later sampled. Therefore, results from the standard, but very time-consuming, method of measuring shear velocity using velocity profiles were compared to results obtained using alternative methods. The alternative methods tested included the use of FST hemispheres, and the prediction of shear velocity from more easily measured hydraulic variables (near-bed velocity, mean velocity, depth and roughness).

Macroinvertebrates were sampled in August and November of 2001 in patches set in a regular arrangement at two sites, a "run site" and a nearby small "riffle site". The densities of macroinvertebrate taxa at the run site were compared to patch substrate size composition, algal cover, different size fractions of detritus and various hydraulic variables. (Abstract shortened by UMI.).