Rapid potential rates of extracellular enzymatic hydrolysis in Arctic sediments

The extracellular enzymatic hydrolysis rates of three fluorescently-labeled polysaccharides (pullulan, laminarin, and xylan) were measured in the upper similar to 11 cm of sediment cores collected near Svalbard in the Arctic Ocean. The three polysaccharides differ in molecular weight (200,000, similar to 6,000, and similar to 8,000 Da for pullulan, laminarin, and xylan, respectively), as well as in monomer composition, linkage position, and anomeric configuration, and are most probably hydrolyzed by distinctly different enzymes. Potential hydrolysis rates of pullulan and laminarin were rapid throughout the sediment cores (average rates of 52 cuts per nmol glucose cm(-3) h(-1) for pullulan, 38 cuts per nmol glucose cm(-3) h(-1) for laminarin) and were comparable to rates measured in sediment cores from more temperate sites. Xylan potential hydrolysis rates were considerably slower at all Svalbard stations (average of 3 cuts per nmol xylose cm(-3) h(-1)). Rapid microbial remineralization of particulate organic carbon requires high levels of extracellular enzyme activity; the high potential hydrolysis rates of fluorescently-labeled pullulan and laminarin in Svalbard sediments demonstrate that at least some types of extracellular enzymes can function rapidly in permanently cold environments.