Heterotrophic bacteria process nearly half of the organic matter produced by phytoplankton in the surface ocean. Much of this organic matter consists of structurally complex polysaccharides, which must initially be hydrolyzed by specific extracellular enzymes to smaller sizes prior to remineralization. Here, we hypothesize that bacterial communities and their enzyme activities reflect available target substrates, which we expect to vary across marine provinces. To test this hypothesis, we concurrently assessed bacterial community composition and activity of polysaccharide hydrolases, as well as carbohydrate abundance and structural complexity at multiple depths and stations in the western North Atlantic. Congruence in monosaccharide composition of particulate organic matter at different stations and depths contrasted with clear structural differences suggested by polysaccharide-specific antibody probing. Bacterial community composition and polysaccharide hydrolase activities also varied by depth and station, suggesting that the structure and function of bacterial communities—as well as the structural complexity of their target substrates—could be interlinked in a complex manner. Our findings reflect the likely underestimation of polysaccharide variation across depth and location due to the low structural resolution of previous carbohydrate analyses. 

Primary Presenter: Chad Lloyd, University of North Carolina at Chapel Hill (cchadlloyd@gmail.com)

Authors:

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

Sarah Brown, University of North Carolina at Chapel Hill  (sbrown21@live.unc.edu)

Greta Giljan, Max Planck Institute for Marine Microbiology  (g.giljan@web.de)

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

Silvia Vidal-Melgosa, Max Planck Institute for Marine Microbiology  (svidal@mpi-bremen.de)

Nicola Steinke,   ()

Margot Bligh, Max Planck Institute for Marine Microbiology  (mbligh@mpi-bremen.de)

Inga Hellige, Max Planck Institute for Marine Microbiology  (ihellige@mpi-bremen.de)

Hagen Buck-Wiese, Max Planck Institute for Marine Microbiology  (hbuck@mpi-bremen.de)

Aman Akeerath Mundanatt, Max Planck Institute for Marine Microbiology  (aakerat@mpi-bremen.de)

Jan-Hendrik Hehemann, Max Planck Institute for Marine Microbiology  (jheheman@mpi-bremen.de)

Rudolf Amann, Max Planck Institute for Marine Microbiology  (ramann@mpi-bremen.de)

Carol Arnosti, University of North Carolina at Chapel Hill  (arnosti@email.unc.edu)