Comparison of Extracellular Protein and Polysaccharide Hydrolysis Between an Arctic and a Temperate Environment

Biomacromolecules like proteins, polysaccharides, and phosphomonoesters account for a large portion of the bioavailable organic carbon and nitrogen in aquatic and terrestrial environments. Despite being relatively ubiquitous, and functioning as metabolic reserves and storage components, these freshly synthesized biomacromolecules are generally too large for heterotrophic microbes to uptake directly without being hydrolyzed by microbial extracellular enzymes. Diverse extracellular hydrolases are present in marine environments, but current assays, such as using singular extracellular peptidase or glycosyl hydrolase, are insufficient to determine total hydrolytic capacity. Therefore, to develop a more complete understanding of extracellular enzymes responsible for hydrolytic activity in marine sediments, several distinct extracellular enzyme substrates were used on sediments from a temperate estuary (the White Oak River estuary, a blackwater drowned river basin in coastal North Carolina, USA) and a high Arctic fjord (Kongsfjorden, in the Svalbard Archipelago, Norway). The hypotheses tested were: (i) bulk activities of enzymes would be lower in Kongsfjorden sediments; (ii) half-saturation constants would differ between the two settings; (iii) ratios of activities of specific enzymes would be different between the two settings; (iv) enzyme diversity would be lower in Kongsfjorden sediments. The experimental results did not support some of the hypotheses. Specifically, bulk enzyme activities were higher in Kongsfjorden sediments compared to the White Oak River sediments, and enzyme diversity was higher in Kongsfjorden sediments. Half-saturation constants were lower in Kongsfjorden, but the differences were not statistically significant, and the ratios of the most active enzymes were different between both environments. Additionally, protein hydrolases were more active than the tested polysaccharide hydrolases at both sites. Suggesting that nitrogen acquisition may be essential for these communities. Kongsfjorden hydrolysis rates were also significantly higher than the White Oak suggesting that temporal variation may play a larger role in this environment.