Image credit: untipografico/Flickr
Glaciers are an important source for many of the world's largest and most significant rivers, but new research is showing that they are also an essential support for the coastal and oceanic food webs.
Dissolved organic matter, some more than 4,000 years old, is discharged by the glaciers and, in spite of its age, has proven to be a highly potent food source for microbes in the ocean.Typically, the potency of organic matter decreases with age. Rick Edwards, a co-author of the recent study, explained that "generally, scientists expect that organic matter decreases in its quality as a food source as it ages, becoming less and less active over time."
The material discharged from the glaciers, however, contradicts this belief. Researchers found that an astonishing 66 percent of the ancient material was immediately metabolized by marine microbes, forming living biomass that helps to support the entire oceanic ecosystem.
Durelle Scott, an assistant professor of biological systems engineering at Virginia Tech who contributed to the research, commented that "the more glacier there is in the watershed, the more carbon is bioavailable. And the higher the percentage of glacier coverage, the older the organic material is." They believe that forests were covered in glaciers between 2,500 and 7,000 years ago and that this material is now emerging from the ice.
The result, Scott explained, is that:
The organic matter in heavily glaciated watersheds is labile, like sugar. Microorganisms appear to be metabolizing ancient carbon and as the microorganisms die and decompose, biodegradable dissolved organic carbon is being flushed out with the glacier melt.
It is a process that has helped fuel one of the most productive salmon fishing regions in Alaska but it also signals a new threat to fragile coastal ecosystems. "Future changes in glacier extent," one researcher cautioned, "may impact the food webs in this region that support some of the most productive fisheries in the United States."
Read more about glaciers:
Black Carbon Identified as a Key Element in Himalayan Glacier Melting
Everest and Himalayan Glaciers Could Vanish By 2035, Imperiling a Billion People
Confirmed: America's Glaciers Shrinking Over Past 50 Years, Warming Climate to Blame