| Summary: | Stable carbon and nitrogen isotopes were used to assess the potential impacts of hydroelectric development and pulp mill activity on benthic food web interactions in the tributaries of the Moose River Drainage Basin in Northeastern Ontario. Secondly, the applicability of stable carbon isotopes as a tool to indicate exposure to pulp mill effluent in wild white sucker ('Catostomus commersoni') located downstream of hydroelectric facilities and pulp mill effluent discharges was assessed. Stable isotope analysis (SIA) of the benthivorous white sucker from an undeveloped tributary (Missinaibi River) showed no significant spatial or temporal variability in the [delta]13C (mean ± SE (n) = -29.3% ± 0.2 (47)) and [delta]15N values (mean ± SE (n) = 8.3% ± 0.1 (47)) of muscle tissue. The range of [delta] 13C (-31.4 to -26.5 96) and [delta]15N (6.3 to 9.4) were used as an indicator of normal fluctuation in the isotopic composition of white sucker in an undeveloped river in the Moose River Basin. Stable isotope analysis of white sucker muscle from a regulated river (Groundhog River) were found to be 13C and 15N depleted upstream of hydroelectric development. Downstream, there were indications (from pre-impoundment and post-impoundment liver comparisons) of 13 C depletion and 15N enrichment of white sucker tissues associated with this recent hydroelectric development (commissioned in fall of 1991). Isotopic trends of white sucker established for the Missinaibi and Groundhog Rivers were used as a reference to determine changes in benthic food web interactions associated with historical log drives and pulp mill effluent discharges on regulated rivers (Mattagami and Kapuskasing Rivers). Bark and wood accumulations from historical log drives did not appear to influence benthic food web dynamics. 13C depleted particulate organic material from upstream of the dam combined with 13C enriched particulate organic material from pulp mill effluent discharges resulted in the combined 13C values detected in white sucker. The ability to ...
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