RAPID POTENTIAL RATES OF EXTRACELLULAR ENZYMATIC-HYDROLYSIS IN ARCTICSEDIMENTS

The extracellular enzymatic hydrolysis rates of three fluorescently-la beled polysaccharides (pullulan, laminarin, and xylan) were measured i n the upper similar to 11 cm of sediment cores collected near Svalbard in the Arctic Ocean. The three polysaccharides differ in molecular we ight (200,000, similar to 6,000, and similar to 8,000 Da for pullulan, laminarin, and xylan, respectively), as well as in monomer compositio n, linkage position, and anomeric configuration, and are most probably hydrolyzed by distinctly different enzymes. Potential hydrolysis rate s of pullulan and laminarin were rapid throughout the sediment cores ( average rates of 52 cuts per nmol glucose cm(-3) h(-1) for pullulan, 3 8 cuts per nmol glucose cm(-3) h(-1) for laminarin) and were comparabl e to rates measured in sediment cores from more temperate sites. Xylan potential hydrolysis rates were considerably slower at all Svalbard s tations (average of 3 cuts per nmol xylose cm(-3) h(-1)). Rapid microb ial remineralization of particulate organic carbon requires high level s of extracellular enzyme activity; the high potential hydrolysis rate s of fluorescently-labeled pullulan and laminarin in Svalbard sediment s demonstrate that at least some types of extracellular enzymes can fu nction rapidly in permanently cold environments.