Scientists from The Ecosystems Center have conducted a program of long-term research at several sites in northern Alaska since 1975. The Centerís arctic research program is based at Toolik Lake, in the northern foothills of the Brooks Range (Fig. 1). The three principal components of the program are: (1) lake studies, (2) river studies, and (3) terrestrial landscape studies. In each of these three areas, long-term monitoring of ecosystem processes (such as primary production) is conducted in order to document their natural variability and to detect trends. Research in each area also includes the monitoring of long-term experiments, designed to help elucidate how major ecosystem processes are controlled. The long-term nature of these experiments also allows us to trace the effects of these manipulations as they cascade up or down, through several trophic levels, over many years. Many of the results of these experiments have been discussed in previous Annual Reports, and the work has led to over 70 scientific publications (seeArctic LTER Web Page).
My part in this larger research program is to understand the role of fish in arctic streams. We have conducted river fertilization (added P & N) in two arctic streams for over 15 years. The purpose of these experiments was to understand how a river system might respond to increased nutrient inputs, such as those that might result from global climate change of disturbance in the watershed (Fig. 3). We found that growth of both adult and age 0 grayling (Thymallus arcticus) was enhanced by nutrient addition. Growth variation between years, however, often exceeds differences caused by nutrient enhancement . Fluctuations in river temperature and discharge (m3/s) may play a role in controlling year to year variation in grayling growth by influencing food availability, energetic demands and prey distribution (Deegan et al., in press). We have also shown that arctic grayling may exert top-down controls in stream ecosystems by predation on insects (Deegan et al. 1997; Golden and Deegan 1998). My current work focuses on the effects on lakes of the immigration of grayling to overwinter.