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We quantified fine-sediment accumulation annually from 2000 to 2003 after culvert construction in five Laurentian Shield streams containing brook trout . A significant spatial pattern (section effect) was observed in which the accumulation was lowest upstream of the culvert (section 1), peaked in the section directly below the culvert (section 2), and slightly decreased in sections further downstream (sections 3-5) without returning to upstream levels. The accumulation was always significantly higher downstream of the culvert than in section 1. The temporal pattern (period effect) was also significant; accumulation was lowest several weeks after construction, peaked at one full year after construction, and decreased at 2-3 years postconstruction. Fine-sediment accumulation differed significantly among all periods. The downstream distance at which sediment accumulation returned to upstream levels varied from 358 and 1,442 m below the culvert. Owing to the accumulated sediment, which probably originates primarily from construction sand or road erosion, habitat downstream of a culvert is in many cases of lower quality for brook trout incubation and rearing. Recommendations for minimizing culvert impacts on fish habitat are discussed. [ABSTRACT FROM AUTHOR]

1. Forestry activities can greatly modify the structure and function of invertebrate communities in streams, but the ability to detect effects of forestry may depend on the spatial scale considered, the choice of response metric and the environmental context. In this study, a multi-scale, multi-metric approach was used to compare the usefulness of proximate and larger-scale measurements of forestry activity for understanding the impacts of forestry on stream macrobenthos. 2. Site-specific responses of macrobenthic communities to forestry activities measured at four spatial scales (sub-basin and 8-, 2- and 0.5-km radii upstream of study sites) were examined for 90 riffle sites distributed among 22 tributary streams (Strahler order 1–5) of the Cascapedia River basin, Quebec, Canada. 3. Multiple regression models and canonical correspondence analysis were used to relate six biological metrics (taxonomic richness, numerical density, biomass density, normalised biomass spectrum, individual body mass and community structure) to variables quantifying logging 1–19 years prior to the study and road density. Environmental predictors (variables quantifying local habitat or landscape features) were included in all analyses to statistically account for environmental context and increase the likelihood of detecting potentially subtle forestry impacts. 4. Forestry activities measured at the larger (sub-basin and 8 km) scales were linked to decline in taxonomic richness, increase in numerical and biomass densities and shift in size structure of benthic macroinvertebrates, indicating that analyses encompassing larger areas, up to the full basin, may allow for more sensitive detection of effects than those of more limited span. 5. These responses primarily reflected marked increases in the abundance of chironomids and decline in the number of trichopteran taxa with increasing areal coverage of recent (≤2–4 years) cuts, suggesting that larger, longer-lived and possibly more specialised taxa were more vulnerable to forestry impacts than smaller, multivoltine, generalist invertebrates. After partialling out the influence of other variables, rapid decline in richness occurred even when <1% of the basin had been clear cut in the year prior to the study. 6. Effects of forestry were detected after statistically accounting for natural environmental variability, which may have otherwise concealed those effects. The combined use of multiple biological metrics, partialling out of environmental effects and measurement of impacts at multiple spatial scales may be a broadly applicable approach for enhancing sensitivity and facilitating interpretation in studies of anthropogenic effects on macroinvertebrate communities. [ABSTRACT FROM AUTHOR]