| Contributors | Affiliation | Role |
|---|---|---|
| Arnosti, Carol | University of North Carolina at Chapel Hill (UNC-Chapel Hill) | Principal Investigator |
| Copley, Nancy | Woods Hole Oceanographic Institution (WHOI BCO-DMO) | BCO-DMO Data Manager |
This dataset includes MCAMUF (glucosidase and peptidase) hydrolysis rates to measure microbial enzyme activities in bulk (not filter-fractionated) seawater. Samples were collected on RV/Sonne cruise SO248 in May 2016. Links to archived CTD data are also provided.
Water was collected via Niskin bottles mounted on a rosette, equipped with a CTD.
Two substrates, -glucose and -glucose linked to a 4-methylumbelliferyl (MUF) fluorophore, were used to measure glucosidase activities. 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 phenylalanine-serine-arginine (FSR) – 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 seven low molecular weight substrates were set up in a 96-well plate. For each substrate, triplicate wells were filled with a total volume of 200 L seawater for experimental incubations; triplicate wells were filled with 200 L autoclaved seawater for killed control incubations. Substrate was added at saturating concentrations. A saturation curve was determined with surface water from each station to determine saturating concentrations of substrate. The saturating concentration was identified as the lowest tested concentration of substrate at which additional substrate did not yield higher rates of hydrolysis. Fluorescence was measured over 24-48 hours incubation time with a plate reader (TECAN spectrafluor plus; 360 nm excitation, 460 emission), with timepoints taken every 4-6 hours. 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. Scripts to calculate hydrolysis rates and produce the figures shown here are available in the associated Github repository [Hoarfrost, 2017].
L = substrate to measure leucine aminopeptidase (L-leucine-7-amido-4 MCA)
AAF = substrate to measure chymotrypsin activity: ala-ala-phe-MCA
AAPF = substrate to measure chymotrypsin activity: N-succinyl-ala-ala-pro-phe-MCA
QAR = substrate to measure trypsin activity: Boc-gln-ala-arg-MCA
FSR = substrate to measure trypsin activity: N-t-boc-phe-ser-arg-MCA
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; time_elapsed from 7 to 0 places
| File |
|---|
SO248_bulk_MCAMUF_joined.csv (Comma Separated Values (.csv), 190.91 KB) MD5:c167b9519194948fd6b8028ff343b72a Primary data file for dataset ID 743224 |
| Parameter | Description | Units |
| station_no | refers to station number for cruise | unitless |
| depth_no | sequence of depths sampled (1 is surface; higher numbers at greater depths) | unitless |
| depth_m | actual depth at which water collected | meters |
| cast_no | cast number (refers to cast of CTD/Niskin bottles on cruise) | unitless |
| ISO_DateTime_UTC | date and time in ISO format (yyyy-mm-ddTHH:MM:SS | unitless |
| Latitude | latitude; north is positive | decimal degreed |
| Longitude | longitude; east is postivie | decimal degreed |
| substrate | Substrates for measurement of enzymatic activities. ara:arabinogalactan: | unitless |
| timepoint | sampling point post-incubation | unitless |
| time_elapsed_hr | incubation time | hours |
| rep1_rate | replicate 1 hydrolysis rate | nanomoles/liter/hour (nmol L-1 h-1) |
| rep2_rate | replicate 2 hydrolysis rate | nanomoles/liter/hour (nmol L-1 h-1) |
| rep3_rate | replicate 3 hydrolysis rate | nanomoles/liter/hour (nmol L-1 h-1) |
| average | average of hydrolysis rates | nanomoles/liter/hour (nmol L-1 h-1) |
| std_dev | std deviation of hydrolysis rates | nanomoles/liter/hour (nmol L-1 h-1) |
| Dataset-specific Instrument Name | |
| Generic Instrument Name | CTD - profiler |
| Generic Instrument Description | The Conductivity, Temperature, Depth (CTD) unit is an integrated instrument package designed to measure the conductivity, temperature, and pressure (depth) of the water column. The instrument is lowered via cable through the water column. It permits scientists to observe the physical properties in real-time via a conducting cable, which is typically connected to a CTD to a deck unit and computer on a ship. The CTD is often configured with additional optional sensors including fluorometers, transmissometers and/or radiometers. It is often combined with a Rosette of water sampling bottles (e.g. Niskin, GO-FLO) for collecting discrete water samples during the cast.
This term applies to profiling CTDs. For fixed CTDs, see https://www.bco-dmo.org/instrument/869934. |
| Dataset-specific Instrument Name | |
| Generic Instrument Name | Fluorometer |
| Generic Instrument Description | A fluorometer or fluorimeter is a device used to measure parameters of fluorescence: its intensity and wavelength distribution of emission spectrum after excitation by a certain spectrum of light. The instrument is designed to measure the amount of stimulated electromagnetic radiation produced by pulses of electromagnetic radiation emitted into a water sample or in situ. |
| Dataset-specific Instrument Name | |
| Generic Instrument Name | Niskin bottle |
| Generic Instrument Description | A Niskin bottle (a next generation water sampler based on the Nansen bottle) is a cylindrical, non-metallic water collection device with stoppers at both ends. The bottles can be attached individually on a hydrowire or deployed in 12, 24, or 36 bottle Rosette systems mounted on a frame and combined with a CTD. Niskin bottles are used to collect discrete water samples for a range of measurements including pigments, nutrients, plankton, etc. |
| Website | |
| Platform | R/V Sonne |
| Start Date | 2016-05-01 |
| End Date | 2016-06-03 |
| Description | Project: Latitudinal and depth-related contrasts in enzymatic capabilities of pelagic microbial communities: Predictable patterns in the ocean?
For related research from this cruise, see https://www.pangaea.de/?q=SO248 |
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.
| Funding Source | Award |
|---|---|
| NSF Division of Ocean Sciences (NSF OCE) |