Table of Contents

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

Samples from the submarine groundwater wells and overlying water column were collected quarterly from November 2022 through March 2024 aboard U.S. Geological Survey (USGS) small boats. This sampling effort was led by collaborator Chris Smith at USGS. Water column samples were collected by lowering the sampling line, acid-cleaned ½” OD Bev-A-Line tubing attached to ¼” synthetic line that was weighed down by a 30 lb kettlebell to target depths. Surface samples were collected at ~1 m depth and bottom samples were collected from ~1 m above the sea floor. A separate sampling line of acid-cleaned 3/8” OD Bev-A-line connected to a custom-made PVC adapter was used for sampling the submarine groundwater wells, which had been installed by USGS. Different Teflon diaphragm pumps were used for the water column and wells samples to avoid cross contamination. Samples for dissolved trace metals were filtered through 0.2 µm Pall Acropak Super membrane filter capsules and collected in acid-cleaned and triple-rinsed 125 mL low density polyethylene (LDPE, Nalgene) bottles. Sample collection and processing for riverine and estuarine end members were accomplished by collaborators from the University of South Florida as described in the related dataset, Conway and Hunt (2026).

All dissolved trace metal samples were acidified within 24 h of collection with ultrapure hydrochloric acid (HCl, Optima) to 0.024 N HCl, double bagged in buckets and stored at room temperature until analyzed at Oregon State University (OSU).

Analysis of dissolved trace metal concentrations

Concentrations of dissolved (<0.2 µm) trace metals, including aluminum (Al), scandium (Sc), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), zinc (Zn), molybdenum (Mo), cadmium (Cd), barium (Ba), lutetium (Lu) and lead (Pb), were analyzed using direct dilution analysis with a Thermo Scientific iCAP-RQ Quadrupole CCT ICP-MS. This instrument is maintained at OSU in the Keck Collaboratory for Plasma Spectrometry.

Samples were diluted 1:20 with 2% nitric acid (HNO₃, Optima) and quantified with nine-point calibration curves made in the same acid matrix but spiked with seawater to match matrix salinity of diluted samples; 1 ppb indium was added to all samples and standards as an internal standard. Reference materials (NASS-7, CASS-6) were measured in each run following the same dilution protocol. Blanks were determined from separate measurements of the 2% HNO₃ matrix including 1 ppb In. Reference material results, averaged blanks and limits of detection are provided in the supplemental Tables.

Sample analyses for trace metals were performed by senior researcher Dr. Salvatore Caprara in the College of Earth, Ocean and Atmospheric Sciences at Oregon State University.

Data were flagged using the SeaDataNet quality flag scheme recommended by GEOTRACES (https://www.geotraces.org/geotraces-quality-flag-policy/) and described below. Notes specific to the application of these flags to this dataset are noted in brackets […].

0: No Quality Control: No quality control procedures have been applied to the data value. This is the initial status for all data values entering the working archive. [Not used].

1: Good Value: Good quality data value that is not part of any identified malfunction and has been verified as consistent with real phenomena during the quality control process. [Used for parameters analyzed in replicate or accompanied by certified reference material analyses. See accompanying Table 1 in the supplemental document for certified reference material values obtained in this study].

2: Probably Good Value: Data value that is probably consistent with real phenomena, but this is unconfirmed or data value forming part of a malfunction that is considered too small to affect the overall quality of the data object of which it is a part. [Used when no replicate measurements and no certified reference were available to check the quality of the data].

3: Probably Bad Value: Data value recognized as unusual during quality control that forms part of a feature that is probably inconsistent with real phenomena. [Not used].

4: Bad Value: An obviously erroneous data value. [Not used].

5: Changed Value: Data value adjusted during quality control. Best practice strongly recommends that the value before the change be preserved in the data or its accompanying metadata. [Not used].

6: Value Below Detection Limit: The level of the measured phenomenon was less than the limit of detection (LOD) for the method employed to measure it. The accompanying value is the detection limit for the technique or zero if that value is unknown. [Values below detection are reported as 0 and should be interpreted using the associated quality flag = 6. Averaged blanks and detection limits for each parameter are provided in accompanying Table 2 in the supplemental document].

7: Value in Excess: The level of the measured phenomenon was too large to be quantified by the technique employed to measure it. The accompanying value is the measurement limit for the technique. [Not used].

8: Interpolated Value: This value has been derived by interpolation from other values in the data object. [Not used].

9: Missing Value: The data value is missing. Any accompanying value will be a magic number representing absent data [Used when no data is available for this parameter].

A: Value Phenomenon Uncertain: There is uncertainty in the description of the measured phenomenon associated with the value such as chemical species or biological entity. [Not used].

- Loaded CSV file BCO-DMO_Buck_STING-LAND_Metals_260206.csv as table "res1" with header row 1, skipping row 2 (units row), treating "", "nd", "na", and "nda" as missing values
- Combined DATE_LOCAL (MM/DD/YY) and TIME_LOCAL (HH:MM) into new datetime column DATETIME_LOCAL_ET using America/New_York timezone (handles both EST and EDT automatically); rows with missing time values produce null
- Created DATETIME_UTC by converting the same DATE_LOCAL and TIME_LOCAL fields from America/New_York timezone to UTC, output as ISO format datetime
- Reformatted DATE_LOCAL from MM/DD/YY to ISO 8601 format %Y-%m-%d (datetime type, UTC)
- Reordered all columns placing identifiers and temporal/spatial columns first, followed by metal concentration groups (Al, Mn, Fe, Co_UV, Co_noUV, Ni, Cu_UV, Cu_noUV, Zn, Mo, Cd, Ba, Lu, Pb), each with their CONC, STDEV, COUNT, and FLAG columns
- Applied find/replace on Ni_D_COUNT to replace "3.0" with "3" to conform to integer type, in line with the other values
- Renamed column TYPE to SITE_TYPE and SAMPLE to SAMPLE_DESC for clarity
- Output written to 997829_v1_sting_endmember_metals.csv

NSF Award Abstract:
This project will investigate how groundwater discharge delivers important nutrients to the coastal ecosystems of the West Florida Shelf. Preliminary studies indicate that groundwater may supply both dissolved organic nitrogen (DON) and iron in this region. In coastal ecosystems like the West Florida Shelf that have very low nitrate and ammonium concentrations, DON is the main form of nitrogen available to organisms. Nitrogen cycling is strongly affected by iron availability because iron is essential for both photosynthesis and for nitrogen fixation. This study will investigate the sources and composition of DON and iron, and their influence on the coastal ecosystem. The team will sample offshore groundwater wells, river and estuarine waters, and conduct two expeditions across the West Florida Shelf in winter and summer. Investigators will participate in K-12 and outreach activities to increase awareness of the project and related science. The project will fund the work of six graduate and eight undergraduate students across five institutions, furthering NSF’s goals of education and training.

Motivated by preliminary observations of unexplained, tightly-correlated DON and dissolved iron concentrations across the West Florida Shelf (WFS), the proposed work will quantify the flux and isotopic signatures of submarine groundwater discharge (SGD)-derived DON and iron to the WFS, and evaluate the bioavailability of this temporally-variable source using four seasonal near-shore campaigns sampling offshore groundwater wells, estuarine, and riverine endmembers and two cross-shelf cruises. The work will evaluate whether SGD stimulates nitrogen fixation on the WFS, and the potential for the stimulated nitrogen fixation to further modify the chemistry of DON and dissolved iron in the region. The cross-shelf cruises will investigate hypothesized periods of maximum SGD and Trichodesmium abundance (June), and reduced river discharge and SGD (February), thus comparing two distinct biogeochemical regimes. The concentrations and isotopic compositions of DON and dissolved iron, molecular composition of DON, and the concentration and composition of iron-binding ligands will be characterized. Nitrogen fixation rates and Trichodesmium spp. abundance and expression of iron stress genes will be measured. Fluxes of DON and iron from SGD and rivers will be quantified with radium isotope mass balances. The impacts of SGD on nitrogen fixation and DON/ligand production will be constrained with incubations of natural phytoplankton communities with submarine groundwater amendments. Two hypotheses will be tested: 1) SGD is the dominant source of bioavailable DON and dissolved iron on the WFS, and 2) SGD-alleviation of iron stress changes the dominant Trichodesmium species on the WFS, increases nitrogen fixation rates and modifies DON and iron composition. Overall, the work will establish connections between marine nitrogen and iron cycling and evaluate the potential for coastal inputs to modify water along the WFS before export to the Atlantic Ocean. This study will thus provide a framework to consider these boundary fluxes in oligotrophic coastal systems and the relative importance of rivers and SGD as sources of nitrogen and iron in other analogous locations, such as coastal systems in Australia, India, and Africa, where nitrogen fixation and SGD have also been documented.

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.