Temperature-Dependent Hydrolytic Activity of Epipelagic Microbial Communities

Microbial communities rely on extracellular enzymes to produce substrates sufficiently small to take into their cells. The activities and structural specificities of these enzymes help determine the lability of organic matter in the ocean. As part of a larger investigation, we measured temperature effects on enzymatic hydrolysis, incubating samples at 4°C to mimic deep sea conditions of sinking particles, and compared those hydrolysis rates to rates at 20°C, a temperature more representative of surface seawater. We focused on polysaccharide hydrolysis, since polysaccharides are common components of marine organic matter. Fluorescently-labeled polysaccharides were incubated in surface water from two stations in the North Atlantic. We found a strong correlation between incubation temperature and hydrolytic activity, with lower hydrolysis rates at lower temperatures. Although the trend was the same for all polysaccharides, the reduction in activity varied considerably by polysaccharide. At the most productive station, laminarin hydrolysis decreased by 32% at a temperature of 4°C, whereas the decrease was only 19% for pullulan and 15% for xylan. These results suggest these three enzyme activities (and the underlying enzymes) differ in their abundance in surface seawater and/or have different susceptibilities to colder temperatures. Surface-derived enzymes that are exported with sinking organic matter therefore likely also have varying levels of activity in the deep sea.

Presentation Preference: Poster

Primary Presenter: Eleanor Hennessey, University of North Carolina at Chapel Hill (ejhennes@unc.edu)

Authors:

Eleanor Hennessey, University of North Carolina at Chapel Hill  (ejhennes@unc.edu)

C. Chad Lloyd, University of North Carolina at Chapel Hill  (cclloyd@unc.edu)

Sherif Ghobrial, University of North Carolina at Chapel Hill  (reef@unc.edu)

John Paul Balmonte, Lehigh University  (jpb422@lehigh.edu)

Carol Arnosti, University of North Carolina at Chapel Hill  (carolarnosti@gmail.com)