ALTERNATIVE LAND USE FUTURES IN THE LOWER PENOBSCOT RIVER WATERSHED: IMPLICATIONS FOR SURFACE WATER QUALITY AND AQUATIC BIOTA

River and stream ecosystems play a critical role in the Maine landscape, linking upland watersheds with downstream aquatic and estuarine ecosystems through flows of water, matter, and energy. Increasingly, rivers and coastal waters are facing pressures and threats associated with human population growth, climate changes, land development, invasive exotic species, and non-point pollution. Given these environmental uncertainties, there is an important need for research aimed at monitoring the ecological health of these ecosystems and detecting changes and trends associated with degradation of aquatic resources. Our investigations indicate that rivers in Maine generally exhibit relatively low background levels of limiting nutrients such as nitrogen and phosphorus, implying that these waters are not currently at risk of eutrophication. These observations are very positive and encouraging, but they also present an important challenge – how do we sustain our healthy river and stream ecosystems in the face of mounting pressures from the expanding human footprint in the Maine landscape? The answer to this question is that what happens in river and stream systems is largely a function of conditions in the surrounding watershed. In a watershed that is managed in a sustainable fashion, risks to surface waters are greatly diminished. We have applied a GIS-based alternative futures modeling approach to examine how different land use change scenarios may affect nutrient transfers from the surrounding watershed to surface waters in the lower Penobscot River. This information will permit improved planning and management for sustaining water quality and aquatic biota.