Hobbie, J. E. Marine Biological Laboratory, jhobbie@llupine.mbl.edu
Peterson, B. J. Marine Biological Laboratory, peterson@lupine.mbl.edu
Bettez, N. Marine Biological Laboratory, nbettez@lupine.mbl.edu
Deegan, L. Marine Biological Laboratory, ldeegan@lupine.mbl.edu
O'Brien, J. University of Kansas, wjob@falcon.cc.ukans.edu
Kipphut, G. W. Murray State Universitiy, gkipphut@lternet.edu

Lakes and streams in the foothills near Toolik Lake, Alaska, at 68 degrees N have been studied since 1975 to predict impacts of global change. Manipulations include whole lake and stream fertilization as well as removal and addition of predators (copepods, lake trout, grayling, sculpin). The following scenario is likely. Warming thaws the upper layers of permafrost; streams become enriched with phosphorus and respond with higher production but grazers keep biomass low. After decades, mosses replace diatoms as the dominant primary producer. Productivity of arctic grayling also rises but it is stressed by warmer temperatures. When temperatures warm, grayling will grow only in summers with higher than average stream flow. In lakes, slight eutrophication leads to increases in the number of trophic levels, especially within the microbial food web. Warmer temperatures increase stratification and decreased oxygen in the hypolimnion could result. Oxygen levels will also decrease in winter under the ice cover. Eventually this habitat change will eliminate the lake trout, a top predator. Removal of lake trout results in a striking increase in abundance and productivity of smaller fish and the emergence of burbot as an alternate top predator. Large species of zooplankton will become virtually extinct.
Day: Tuesday, Feb. 2
Time: 02:45 - 03:00pm
Location: Eldorado Hotel
Code: SS15TU0230E