DIATOM AND CHRYSOPHYTE ALGAL RESPONSE TO LONG-TERM PCB CONTAMINATION FROM A POINT-SOURCE IN NORTHERN LABRADOR, CANADA

摘要

The long-term response of diatom and chrysophyte communities to local PCB contamination was examined in an impacted and reference lake in northern Labrador. Beginning in the late 1950s, lake Saglek-2 (SK-2) received direct inputs of the contaminant in runoff, leaving a record of rising PCB concentrations in lake sediments. An examination of sediment samples spanning the past ～ 150 yr revealed chrysophyte and diatom assemblages characteristic of clear, slightly acidic, oligotrophic lakes, but surprisingly little change in either community was observed through time. The lack of response may be explained by several factors. For example, elevated PCB concentrations in lake sediments may not reflect bioavailable concentrations in lakewater. Therefore, realized concentrations may be too low to exhibit detrimental effects in phytoplankton communities. Our findings do, however, have important implications for studies of climate change in circumpolar regions. First, we provide additional evidence that climatic change has been minimal in northern Labrador, in contrast to changes observed in other Arctic and sub-Arctic regions. Second, our findings support the notion that recent, marked changes in species composition observed in other Arctic lakes are the result of recent climate change and not caused by the contamination of lakes from the long-range transport of pollutants.