Table of Contents

• Coverage
• Dataset Description
  • Methods & Sampling
  • Data Processing Description
  • BCO-DMO Processing Description
• Related Publications
• Parameters
• Instruments
• Project Information
• Funding

Surface water samples were collected on five consecutive one-day trips aboard R/V Trident along a transect from the Port of Houston to the Galveston Bay entrance following Hurricane Harvey from September 4 to September 28, 2017. Samples were filtered on board through 0.2-micrometer (μm) Whatman-Nucleopore Q-TEC filters (Filtration Solutions) for DOC, optical, and chemical analysis.

Samples for mass spectrometry analyses (900 milliliters (mL)) were acidified to pH 2.5 using 6 moles per liter (mol L-1) sulfuric acid and extracted through Agilent PPL cartridges (1 gram) at 10 milliliters per minute (mL min-1). After extraction, cartridges were rinsed with 10 mL of deionized water acidified to pH 2.5 and dried for 30 seconds to remove residual water. The cartridges were eluted with 20 mL of methanol at 2 mL min-1, and the eluate was stored in glass vials at -20 degrees Celsius until analysis.

Electrospray ionization mass spectrometry (ESI-MS) experiments were performed using a Thermo Scientific Q Exactive Focus. Sample was injected into a 10-microliter (µL) loop and was transferred to the mass spec using a mobile phase containing 70% methanol and 30% water with 0.1% formic acid at a flow rate of 600 microliters per minute (µL/min). The Q Exactive Focus HESI source was operated in full MS in positive mode and negative mode. The mass resolution was tuned to 70000 FWHM at m/z 200. The spray voltage was set to 3.5 kilovolts (kV) for positive mode and 2.8 kV for negative mode. The sheath gas and auxiliary gas flow rates were set to 40 and 10 arbitrary units, respectively. The vaporizer and transfer capillary temperatures were held at 250 and 320 degrees Celsius, respectively. The S-Lens RF level was set at 50 volts. Exactive Series 2.11 /Xcalibur 4.2.47 software was used for data acquisition and processing of profile data. Mass spectral data processing for molecular formulae assignment followed procedures outlined by Hawkes et al. (2020). This included noise removal, internal calibration, and contaminant or rare peak removal. MATLAB code adapted from Fu et al. 2020) was used to assign formulae to noise-filtered and calibrated peaks. Assignment was performed allowing a mass tolerance of ± 2 parts per million (ppm).

Mass spectrometry data were processed with Matlab code provided in Fu et al. (2020). Final data were prepared with Anaconda Python distribution 2023.09-0, Python version 3.11.5.

- Imported original file "MS_data_GB.csv" into the BCO-DMO system.
- Renamed fields to comply with BCO-DMO naming conventions.
- Saved the final file as "983645_v1_mass_spec_galveston_bay.csv".

NSF Award Abstract:
Collaborative Research: Distribution and Cycling of Carboxyl-Rich Alicyclic Molecules (CRAM) in the Ocean

Dissolved organic matter is the largest pool of organic carbon in the ocean. Thus, it plays an important role in carbon storage and climate change. The components of dissolved organic matter are the remains of biological products. As a result, the chemical make-up of dissolved organic matter (DOM) can provide important clues about the processes affecting this carbon pool. By learning more about the chemical structures and reactions that produce DOM, connections can be made to biological and biochemical processes and their importance. This project will study the distribution, production, and removal of one important class of molecules called carboxyl-rich alicyclic molecules (CRAM). These molecules are abundant in marine DOM and play an important role in the ocean carbon cycle. They also affect the supply of the micronutrient iron, and thus have an important influence on primary production and ocean food webs. The research includes field and laboratory experiments and takes advantage of ocean locations with long-term data. Together, the lead scientists will provide training and resources for the graduate students, undergraduate research opportunities for underrepresented groups in STEM, and direct outreach to the public through a website, articles in local newspapers, and talks at public venues.

CRAM make-up 8 to 25% of marine dissolved organic carbon (DOC) and represent a carbon reservoir of >65 Pg C that is equivalent to at least 8% of the atmospheric CO2 pool. CRAM play a central role in the functioning of the microbial carbon pump, a conceptual framework for producing refractory carbon by microbial processes in the ocean. Further, CRAM act as an important ligand of Fe(III) in the ocean, thereby playing an important role in regulating marine primary production. The main project objectives are: (1) measure the variable distribution of CRAM in the ocean, and (2) determine the dominant mechanisms of CRAM production and removal. The project will leverage an extensive set of already collected samples across the world’s oceans and new field work within the framework of the Bermuda Atlantic and Hawaii Ocean Time Series. Field measurements will be combined with experimental approaches to specifically address microbial and photochemical reactions leading to CRAM production and removal. This research will fill important gaps in resolving the key questions about organic carbon cycling in the ocean and explore the role of DOM in mediating the cycles of iron and other trace elements.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.