Lability of dissolved organic carbon in Arctic rivers on the North Slope of Alaska

Abstract

Rivers are an important pathway of organic carbon-mobilization in the arctic, and their influence is projected to grow as precipitation and soil temperatures increase in response to highlatitude warming. This study addresses the bioactivity of arctic riverine dissolved organic carbon (DOC) in three North Slope Alaskan rivers: the Kuparuk, the Colville, and the Sagavanirktok. While lability experiments have previously been conducted during late summer discharge on arctic rivers, none have analyzed the early hydrograph spring-melt peak DOC. During the summer of 2006, water samples were taken from significant periods of the hydrograph (upswing, peak, downswing, and quasi-stable summer) of the three rivers for DOC lability experiments. DOC from spring melt discharge proved to be highly labile and therefore dynamically different from summer DOC. Over a three-month sample incubation period, these samples lost up to 40 and 33 percent of their DOC (with and without added nutrients, respectively) while samples taken later in summer lost merely 9 and 5 percent. As spring melt contributes half of the total annual discharge and DOC flux of winter-freezing rivers, a significant portion of annual arctic DOC is labile and is therefore a large input of bioactive organic DOC to the Arctic Ocean carbon cycle.