Rivers fringing the gulf coast of Alaska discharge as much water as the Mississippi River into a marine system that harbors the most productive salmon fishery in the world. As these rivers flow through the temperate rain forests on the coastal margin, they are influenced by vegetation, soils and wetlands, which control the amount and timing of carbon and nutrients delivered to the productive coastal ecosystems receiving that drainage.
"Understanding how these various watersheds respond to management activities and climate change is essential in mitigating the impacts of a warming climate on habitat quality within rivers and productivity within the adjacent marine ecosystem," explains Edwards.
"We don't currently have much information about how runoff from glaciers may be contributing to productivity in downstream marine ecosystems," said Hood. "This is a particularly critical question given the rate at which glaciers along the Gulf of Alaska are thinning and receding."
Highlights of the study include:
The greater the amount of glacier in the watershed, the older the dissolved organic matter and the more available it is to marine organisms.
These results support the hypotheses that microbial communities beneath the glaciers grow on soils and forests overrun by the glaciers during the Hypsithermal warm period (between 7,000-2,500 years ago). As they degrade the ancient material, they make new food from old carbon.
The quality of the dissolved organic matter is so high that 23 to 66 percent is used by marine micro-organisms and incorporated into food webs supporting higher organisms.
As glaciers recede and disappear, the input of this valuable food source will decrease with unknown impacts on productivity of marine food webs.
|Contact: Sherri Richardson Dodge|
USDA Forest Service, Pacific Northwest Research Station