Tracking water quality changes related to human activities in Cape Breton Highlands National Park (Nova Scotia,Canada) using paleolimnological techniques

摘要

Assessing the extent of environmental change in national parks is crucial to their mandate of preserving ecological integrity and restoring ecosystems to as close to their natural, preanthropogenic states as possible (PARKS CANADA 2001). While this goal is important, it can come into conflict with the development of infrastructure necessary for use of the park by visitors. Both are important reasons for the establishment of many parks as well as a key source for revenue. However, a lack of detailed long-term ecological data makes it difficult to accurately determine the original ( i.e., pre-disturbance) characteristics of park ecosystems, and the degree of natural versus anthropogenic variability. Fortunately, in aquatic systems, sediments often preserve a surprisingly rich archive of past lake communities, as well as geochemical and physical proxy indicators, that can be used by paleolimnologists to reconstruct past environmental conditions (SmoL 2002). Using dated lake sediment cores, paleolimnologists can provide important insights into past ecological and other environmental changes for which direct observational data are not available. For example, has the lake changed due to human impacts? If so, when and by how much? What were the pre-disturbance or reference conditions for the study site in question? Although a wide spectrum of physical, chemical, and biological indicators are available, most biological-based assessments use changes in diatom (Bacillariophyceae) species assemblages to infer past limnological conditions because their siliceous valves are often abundant, diverse, and well-preserved in sediments, and the ecological optima of many common taxa have been described (BATTARBEE et al. 1999, HALL & Smoi. 1999). These paleolimnological techniques can provide important data to park ecologists and lake managers to determine how ecosystems have changed over time, and how they have been impacted by environmental stressors. We used paleolimnological techniques to assess the environmental impacts of cultural activities around 2 lakes in Cape Breton Highlands National Park (Fig. I), which are of concern to park ecologists. French Lake is situated very close to a scenic highway, and concerns were raised that it may have been impacted by road construction and the subsequent run-off of road salt (used to keep the road passable during winter). Freshwater Lake is located on the Atlantic coast and surrounded by park recreational areas (e.g., beaches, picnic areas, cottages). While previous paleolimnological studies of Nova Scotia lakes have included lakes in Cape Breton Highlands National Park, these have focused on the effects of acidic deposition and recent climatic changes (GINN et al. 2007a, 2007b). To date, no work has been published on the effects of more local watershed activities on the long-term changes in these park lakes.