Effects of shoreline logging on the epilithic algal community in small Canadian Shield lakes with logged catchments

Abstract

Study area : Coldwater Lakes experimental watersheds area within the boreal-Great Lakes transition forest on the Precambrian shield 200 km northwest of Thunder Bay and 70 km northwest of Atikokan, northwestern Ontario. Lakes L26, L39 and L42. Chlorophyll 'a' was used to index algal biomass ; carbon, nitrogen and phosphorus were used to measure nutritional status, and community characteristics were evaluated using areal densities of taxonomic classes. Littoral zones were described using water turbulence index, littoral wind measurements, and mass measurements of epilithic material, etc.

Chlorophyll a, nutritional status and community characteristics of epilithic algae in littoral zones of three small Canadian Shield lakes with logged watersheds were assessed. Sites were chosen with different shoreline treatments, logged or unlogged shoreline forest, to estimate impacts of shoreline logging on epilithic algal communities. All three lakes had logged watersheds, and L42 and L39 had experienced some shoreline logging. No shoreline logging had been done on L26, but two sites were used with characteristics similar to logged and unlogged shoreline forest. Chlorophyll a (chi a) was used to index algal biomass; carbon (C), nitrogen (N) and phosphorus (P) were used to measure nutritional status; and, community characteristics were evaluated using areal densities of taxonomic classes. Littoral zones were described using a water turbulence index and littoral wind measurements, mass measurements of epilithic material including organic and inorganic components and changes in light (theoretical) and tem perature (actual) environments following shoreline logging. The only significant differences in measured variables were found at sites in L39, with higher levels of total and organic material, chi a, C and N at the site with logged shoreline forest. Further, Chlorophyceae, Bacillariophyceae, Xanthophyceae and Dinophyceae were higher and Cyanophyceae were lower in L39 a t the site with logged shoreline forest. No differences were found between treatment sites in L42, or between sites in L26. Differences found in L39 may have been due more to inter-site variation than to shoreline logging. Overall, data did not show evidence of impacts to epilithic algal communities or littoral environments from shoreline logging, however, results were not conclusive given the preliminary nature and short time-span of the study.