Glaciers as a source of ancient and labile organic matter to the marine environment.

Abstract

Riverine organic matter supports of the order of one-fifth of estuarine metabolism. Coastal ecosystems are therefore sensitive to alteration of both the quantity and lability of terrigenous dissolved organic matter (DOM) delivered by rivers. Here we characterize streamwater DOM from 11 coastal watersheds on the Gulf of Alaska that vary widely in glacier coverage. In contrast to nonglacial rivers, we find that the bioavailability of DOM to marine microorganisms is significantly correlated with increasing ¹⁴C age. Moreover, the most heavily glaciated watersheds are the source of the oldest and most labile DOM. These glacial watersheds have extreme runoff rates, in part because they are subject to some of the highest rates of glacier volume loss on Earths. Glacial runoff is a quantitatively important source of labile reduced carbon to marine ecosystems. Moreover, because glaciers and ice sheets represent the second largest reservoir of water in the global hydrologic system, our findings indicate that climatically driven changes in glacier volume could alter the age, quantity and reactivity of DOM entering coastal oceans.

Citation

Hood, E.; Fellman, J.; Spencer, R.G.M.; Hernes, P.J.; Edwards, R.; D'Amore, D.; Scott, D.2009. Glaciers as a source of ancient and labile organic matter to the marine environment. Nature. 462(24/31): 1044-1048.