Size-fractionated chlorophyll-a data from samples collected during R/V Savannah cruises conducted in the South Atlantic Bight off the coast of Georgia from 2015-2017

Website: https://www.bco-dmo.org/dataset/816278
Data Type: Cruise Results
Version: 1
Version Date: 2020-06-19

Project
» RUI: Vitamin B12 and nitrogen regulation of oceanic dimethylsulfoniopropionate and dimethylsulfide (B12 Impacts on DMSP)
ContributorsAffiliationRole
Lee, PeterCollege of Charleston - Hollings Marine Lab (CoC-HML)Principal Investigator
Rauch, ShannonWoods Hole Oceanographic Institution (WHOI BCO-DMO)BCO-DMO Data Manager

Abstract
Size-fractionated chlorophyll-a data collected during several R/V Savannah cruises conducted from 2015 to 2017 along a transect from shelf waters to oligotrophic waters in the South Atlantic Bight off the coast of Georgia (Navy Op Area NA06).


Coverage

Spatial Extent: N:31.42113 E:-76.343633 S:31.031829 W:-81.121513
Temporal Extent: 2015-03-16 - 2017-01-27

Dataset Description

Size-fractionated chlorophyll-a data collected during several R/V Savannah cruises conducted from 2015 to 2017 along a transect from shelf waters to oligotrophic waters in the South Atlantic Bight off the coast of Georgia (Navy Op Area NA06).


Acquisition Description

All samples were pre-screened through a 202 µm Nitex mesh. Size-fractionated Chlorophyll a (Chl-a) samples were collected by passing discrete 1 L aliquots of seawater through Nitex with mesh sizes of 63 and 20 µm, and collecting the filtrate. The filtrate was then filtered under low vacuum through GF/F (Sterlitech) filters. An additional sample was directly filtered onto a GF/F filter for total Chl-a. The filters were extracted in 90% acetone overnight at -20°C and analyzed according to the protocol described by Welschmeyer (1994). The size classes were calculated by difference (total, > 63 µm, 63-20 µm, < 20 µm). nd = no data


Processing Description

BCO-DMO Processing:
- renamed fields;
- added date/time field in ISO8601 format.


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Related Publications

Welschmeyer, N. A. (1994). Fluorometric analysis of chlorophyll a in the presence of chlorophyll b and pheopigments. Limnology and Oceanography, 39(8), 1985–1992. doi:10.4319/lo.1994.39.8.1985
Methods

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Parameters

ParameterDescriptionUnits
Cruise_IDCruise Identifier unitless
Station_IDStation number unitless
UTC_DateStart date for sample collection; Coordinated Universal Time; Format: MM/DD/YYYY unitless
UTC_TimeStart time for sample collection; Coordinated Universal Time; Format: hh:mm:ss unitless
ISO_DateTime_UTCStart date and time of sample collection formatted to ISO8601 standard: YYYY-MM-DDThh:mm:ssZ unitless
LatitudeStart latitude for sample collection; Negative = South decimal degrees North
LongitudeStart longitude for sample collection; Negative = West decimal degrees East
Bottom_DepthBottom depth from ship's sonar meters (m)
DepthSample depth from CTD readout meters (m)
Total_Chl_aTotal chlorophyll-a concentration micrograms per liter (ug/L)
gt_63_umChlorophyll-a concentration in plankton greater than 63 micrometers micrograms per liter (ug/L)
bw_63_20_umChlorophyll-a concentration in plankton in size range 20-63 micrometers micrograms per liter (ug/L)
lt_20_umChlorophyll-a concentration in plankton smaller than 20 micrometers micrograms per liter (ug/L)


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Instruments

Dataset-specific Instrument Name
Niskin bottle
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.

Dataset-specific Instrument Name
SBE-25 CTD
Generic Instrument Name
CTD Sea-Bird 25
Generic Instrument Description
The Sea-Bird SBE 25 SEALOGGER CTD is battery powered and is typically used to record data in memory, eliminating the need for a large vessel, electrical sea cable, and on-board computer. All SBE 25s can also operate in real-time, transmitting data via an opto-isolated RS-232 serial port. Temperature and conductivity are measured by the SBE 3F Temperature sensor and SBE 4 Conductivity sensor (same as those used on the premium SBE 9plus CTD). The SBE 25 also includes the SBE 5P (plastic) or 5T (titanium) Submersible Pump and TC Duct. The pump-controlled, TC-ducted flow configuration significantly reduces salinity spiking caused by ship heave, and in calm waters allows slower descent rates for improved resolution of water column features. Pressure is measured by the modular SBE 29 Temperature Compensated Strain-Gauge Pressure sensor (available in eight depth ranges to suit the operating depth requirement). The SBE 25's modular design makes it easy to configure in the field for a wide range of auxiliary sensors, including optional dissolved oxygen (SBE 43), pH (SBE 18 or SBE 27), fluorescence, transmissivity, PAR, and optical backscatter sensors. More information from Sea-Bird Electronics: http:www.seabird.com.

Dataset-specific Instrument Name
Sea-Bird Scientific SBE 911 CTD carousel
Generic Instrument Name
CTD Sea-Bird 911
Generic Instrument Description
The Sea-Bird SBE 911 is a type of CTD instrument package. The SBE 911 includes the SBE 9 Underwater Unit and the SBE 11 Deck Unit (for real-time readout using conductive wire) for deployment from a vessel. The combination of the SBE 9 and SBE 11 is called a SBE 911. The SBE 9 uses Sea-Bird's standard modular temperature and conductivity sensors (SBE 3 and SBE 4). The SBE 9 CTD can be configured with auxiliary sensors to measure other parameters including dissolved oxygen, pH, turbidity, fluorescence, light (PAR), light transmission, etc.). More information from Sea-Bird Electronics.

Dataset-specific Instrument Name
Turner Designs 10AU Fluorometer
Generic Instrument Name
Turner Designs Fluorometer 10-AU
Generic Instrument Description
The Turner Designs 10-AU Field Fluorometer is used to measure Chlorophyll fluorescence. The 10AU Fluorometer can be set up for continuous-flow monitoring or discrete sample analyses. A variety of compounds can be measured using application-specific optical filters available from the manufacturer. (read more from Turner Designs, turnerdesigns.com, Sunnyvale, CA, USA)


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Deployments

SAV-15-04

Website
Platform
R/V Savannah
Start Date
2015-03-15
End Date
2015-03-21
Description
More information is available from Rolling Deck to Repository (R2R): https://www.rvdata.us/search/cruise/SAV-15-04

SAV-15-16

Website
Platform
R/V Savannah
Start Date
2015-06-20
End Date
2015-06-26
Description
More information is available from Rolling Deck to Repository (R2R): https://www.rvdata.us/search/cruise/SAV-15-16

SAV-15-20

Website
Platform
R/V Savannah
Start Date
2015-08-07
End Date
2015-08-13
Description
More information is available from Rolling Deck to Repository (R2R): https://www.rvdata.us/search/cruise/SAV-15-20

SAV-15-26

Website
Platform
R/V Savannah
Start Date
2015-10-13
End Date
2015-10-19
Description
More information is available from Rolling Deck to Repository (R2R): https://www.rvdata.us/search/cruise/SAV-15-26

SAV-16-06

Website
Platform
R/V Savannah
Start Date
2016-03-06
End Date
2016-03-12
Description
More information is available from Rolling Deck to Repository (R2R): https://www.rvdata.us/search/cruise/SAV-16-06

SAV-16-22

Website
Platform
R/V Savannah
Start Date
2016-06-21
End Date
2016-06-27
Description
More information is available from Rolling Deck to Repository (R2R): https://www.rvdata.us/search/cruise/SAV-16-22

SAV-16-28

Website
Platform
R/V Savannah
Start Date
2016-08-15
End Date
2016-08-21
Description
More information is available from Rolling Deck to Repository (R2R): https://www.rvdata.us/search/cruise/SAV-16-28

SAV-17-02

Website
Platform
R/V Savannah
Start Date
2017-01-21
End Date
2017-01-27
Description
More information is available from Rolling Deck to Repository (R2R): https://www.rvdata.us/search/cruise/SAV-17-02


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Project Information

RUI: Vitamin B12 and nitrogen regulation of oceanic dimethylsulfoniopropionate and dimethylsulfide (B12 Impacts on DMSP)

Coverage: North Atlantic Ocean in the South Atlantic Bight off the coast of Georgia; Navy Op Area NA06


Description from NSF award abstract: Vitamin B12 and nitrogen are nutrients critical to phytoplankton growth. Since B12 is produced solely by bacteria, phytoplankton must acquire their B12 from bacteria. Nitrogen is used to produce the amino acid methionine and B12 is required by the enzymes that form methionine. Methionine is the precursor to the algal metabolite dimethylsulfoniopropionate (DMSP). Bacteria degrade this compound to the climatically-active compound dimethylsulfide (DMS). Subsequent DMS transfer into the atmosphere is considered a significant driver of cloud formation and a possible climate feedback mechanism. DMSP can also be degraded via a secondary pathway to form methylmercaptopropionate (MMPA), which is not released to the atmosphere. Consequently, DMSP formation and the extent of DMSP degradation to DMS or MMPA are susceptible to B12 availability. Nitrogen availability influences this effect by controlling methionine production. Thus, the overarching premise for this study is that B12 availability regulates oceanic DMSP and DMS formation, and is synergistically impacted by nitrogen limitation. By providing a mechanistic understanding of relevant biogeochemical parameters this study will significantly improve the incorporation of sulfur-related microbial processes into climate models. This project will combine established biogeochemistry-based measurements with cutting-edge metabolomics, transcriptomics and proteomics techniques in laboratory and field studies. Culture experiments will examine the interactive effect of B12 and nitrogen availability on DMSP formation in several ecologically-relevant phytoplankton taxa. Second, the microbial degradation of DMSP and DMS in relation to B12 availability will be examined using several environmentally-important bacteria and archaea. Finally, field studies will examine the seasonal variability of B12, DMSP and DMS, and the relative importance of DMS and MMPA formation in the South Atlantic Bight. Gene and protein expression will be assessed at each level of this study to identify gene products, metabolic pathways, and cellular mechanisms underlying the interconnections between B12, sulfur, and nitrogen cycles. The results generated will have a major impact on current understanding of the role of B12 and nitrogen on the DMSP and DMS cycling, as well as the potential role of these stressors in global climate change. In addition to providing evidence for microbe-based mechanisms behind the modulation of oceanic DMS, this project will (1) furnish an explanation for "summer DMS paradox", thus having significant implications for the development of future DMS models, (2) assess the interactive impact of B12 and nitrogen availability on intracellular DMSP production and (3) provide insight as to whether B12 may play a far more critical role in modulating climate feedback mechanisms on phytoplankton productivity.


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Funding

Funding SourceAward
NSF Division of Ocean Sciences (NSF OCE)

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