Table of Contents

• Coverage
• Dataset Description
  • Methods & Sampling
  • Data Processing Description
• Data Files
• Related Publications
• Parameters
• Instruments
• Deployments
• Project Information
• Funding

This dataset includes microbial peptidase hydrolysis rates measured on particles collected from gravity filtered seawater. Links to archived CTD data are also provided. Five substrates linked to a 7-amido-4-methyl coumarin (MCA) fluorophore, one amino acid – leucine – and four oligopeptides – the chymotrypsin substrates alanine-alanine-phenylalanine (AAF) and alanine-alanine-proline-phenylalanine (AAPF), and the trypsin substrates glutamine-alanine-arginine (QAR) and glutamic acid-gylcine-arginine (EGR) – were used to measure exo- and endo-acting peptidase activities, respectively.

Water was collected via Niskin bottles mounted on a rosette, equipped with a CTD.

Experiments on (operationally defined) particles were carried out by gravity-filtering water through 3 um pore size filters. 1/12th sections of the 3 um pore-size filters were submerged in 15 mL artificial seawater; enzyme activities were measured as described below.

Five substrates linked to a 7-amido-4-methyl coumarin (MCA) fluorophore, one amino acid – leucine – and four oligopeptides – the chymotrypsin substrates alanine-alanine-phenylalanine (AAF) and alanine-alanine-proline-phenylalanine (AAPF), and the trypsin substrates glutamine-alanine-arginine (QAR) and glutamic acid-gylcine-arginine (EGR) – were used to measure exo- and endo-acting peptidase activities, respectively. Hydrolysis rates of the substrates were measured as an increase in fluorescence as the fluorophore was hydrolyzed from the substrate over time [as in Hoppe, 1993; Obayashi and Suzuki, 2005]. Incubations with the 5 low molecular weight substrates were set up in 4 ml cuvettes. For particle-associated incubations, 1/12th of a filter was submerged in 4 ml artificial seawater in a cuvettes; substrates were added at 100 micromolar concentrations. Fluorescence was measured at 0, 4, 8, and 12 h.

 Substrate was added 100 micromolar concentrations. Fluorescence was measured over at 0 hrs, 24 h, 48h, and 72 h, using a mini fluorimeter. Hydrolysis rates were calculated from the rate of increase of fluorescence in the incubation over time relative to a set of standards of known concentration of fluorophore.

All incubations were conducted at 0 C in the dark.

BCO-DMO Processing Notes:
- added conventional header with dataset name, PI name, version date
- reduced decimal precision of rate columns from 9 to 6 places

NSF Award Abstract:
Heterotrophic microbial communities are key players in the marine carbon cycle, transforming and respiring organic carbon, regenerating nutrients, and acting as the final filter in sediments through which organic matter passes before long-term burial. Microbially-driven carbon cycling in the ocean profoundly affects the global carbon cycle, but key factors determining rates and locations of organic matter remineralization are unclear. In this study, researchers from the University of North Carolina at Chapel Hill will investigate the ability of pelagic microbial communities to initiate the remineralization of polysaccharides and proteins, which together constitute a major pool of organic matter in the ocean. Results from this study will be predictive on a large scale regarding the nature of the microbial response to organic matter input, and will provide a mechanistic framework for interpreting organic matter reactivity in the ocean.

Broader Impacts: This study will provide scientific training for undergraduate and graduate students from underrepresented groups. The project will also involve German colleagues, thus strengthening international scientific collaboration.