As tidewater glaciers beat a hasty retreat up Glacier Bay in southeast Alaska, they uncover rocky, barren landscapes and feed cold lakes and streams -- new habitat for life's hardy explorers. In the October issue of Ecology, researchers from the Universities of Birmingham, Roehampton and Leeds describe the evolution and assembly of a stream ecosystem in newly de-glaciated terrain, from early insect and crustacean invaders to the arrival of migrating salmon.
Sampling began at Stonefly Creek in the early 1990s, after retreating ice, a remnant of the lost Plateau Glacier, began revealing the creek's lower reaches in the late 1970s. Together with work at nearby Wolf Point Creek the study is the most complete and long-running catalog of stream development.
Now originating in a clearwater lake, Stonefly Creek tumbles over falls, fills a second, murkier lake, and merges with a stream from a third pond and wetlands before emptying into Wachusett Inlet. This complex geography, the researchers found, buffers the young stream from abrupt changes in water level and provides a diversity of habitats that welcome species with different specialties. Twenty-seven species of tiny crustaceans, armored aquatic animals from the same big family as barnacles, crabs and krill, arrived without obvious means of transport. Within ten years, pink salmon and Dolly Varden char had established spawning grounds in the stream. Coho (silver) salmon, Sockeye (red) salmon, and other fish species followed.
Shrinking glaciers are changing large expanses of northern coastline. The speed and pattern of colonization across Stonefly Creek's watershed will aid our understanding of watershed restoration and conservation of biodiversity in a changing climate.
"Salmon stocks are under threat and decline in many regions of the world due to human activities," said lead author Alexander Milner. "The creation of these new runs has important potential to help balance the losses."
- Alexander M. Milner, Anne L. Robertson, Lee E. Brown, Svein Harald Sønderland, Michael McDermott, Amanda J. Veal. Evolution of a stream ecosystem in recently deglaciated terrain. Ecology, 2011; 92 (10): 1924 DOI: 10.1890/10-2007.1
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