Table of Contents

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

Nutrient samples at each depth were collected directly from Niskin bottles through a 0.2 μm capsule filter (Pall Supor®) using a peristaltic pump at pressures ≤5 mm Hg. Filtrate was collected directly into two 50 mL sterile polypropylene centrifuge tubes (Falcon®) to measure nitrate (NO3–), nitrite (NO2–), orthophosphate ions (simplified as PO4, sum of HPO42– and PO43–), and urea concentrations. Filtrate was also pumped into three 2 mL sterile polypropylene tubes for cyanate determinations, two 15 mL OPA-treated polypropylene tubes (Falcon®) for ammonium (NH4+) analyses, and two 40 mL combusted amber glass vials for analysis of total dissolved free primary amine. To minimize contamination from filtration and between samples, filters and tubing were rinsed thoroughly with site water before sample collection. NO3–+ NO2–, NO2–, PO4, and urea samples (duplicates) were stored at 4 °C until analysis within 48 hours of their collection using a nutrient autoanalyzer (Astoria-Pacific, Inc., USA) according to the manufacturer’s specifications. The method detection limits for NO3–+ NO2–, NO2–, PO4, and urea were 0.14 μmol L–1, 0.07 μmol L–1, 0.03 μmol L–1, and 0.08 μmol L–1, respectively. NH4+ samples (duplicates) were kept at 4 °C until analysis within 24 hours of collection. The concentrations of NH4+ were measured onboard using the OPA-fluorescence method of Holmes et al. (1999) with a spectrofluorometer. The method detection limit was 10.0 nmol L–1. Cyanate samples (triplicates) were stored in liquid nitrogen aboard the ship and at -80 °C once samples were returned to the land-based laboratory. Cyanate concentrations were measured by high-performance liquid chromatography (HPLC) using a precolumn fluorescence derivatization method (Widner et al., 2013; Widner and Mulholland, 2017). The method detection limit was 0.4 nmol L–1.

- Removed row from data containing unit information
- Changed second "Density" column header name to "Density_sigma_t"
- Rounded latitude and longitude values to 6 degrees of precision
- "No data" values in the primary data file are represented by blank values in cells (NAs were removed from the original data presentation)
- Merged separate date and time columns into one datetime column called ISO_DateTime_UTC

NSF Award Abstract:

Nitrogen is a critical nutrient in the world's oceans because, among other things, it is a major component of living organisms and can be a driver in primary productivity. Nitrogen is present in the ocean in a number of organic and inorganic forms, which vary in their ease in being assimilated by marine organisms. Cyanate is a simple form of organic nitrogen present in the ocean, although its abundance and importance to the ocean nitrogen cycle is poorly understood. Using newly developed and tested methods for measuring ambient cyanate concentrations and its uptake in seawater, researchers will analyze the distribution, sources, and geochemistry of cyanate in shelf waters of the Atlantic Ocean. Results from this project will elucidate the importance of cyanate in the marine nitrogen cycle and transform understanding of cyanate production and assimilation in the sea. This project will provide a unique opportunity for both graduate student research and undergraduate training, and will likely expose underrepresented groups to marine sciences.

Although physiological and genomic evidence suggest that marine microbes can utilize a broad array of inorganic and organic nitrogen compounds, cyanate's role in the marine nitrogen cycle has not yet been examined. As one of the simplest organic nitrogen compounds, cyanate has likely been present in the environment over Earth's long history. Evidence suggests that cyanate metabolism appeared early on in bacterial genomes and thus, the study of cyanate assimilation in the contemporary ocean may illuminate microbial processes with deep evolutionary roots. However, a decade since discovering the genomic capacity for cyanate utilization in marine cyanobacteria, little is still known about cyanate distributions in the environment, how it is produced, and how widespread cyanate utilization is among marine microbes. To further understanding of cyanate's role in the marine nitrogen cycle, a combination of geochemical approaches will be used to assess: 1) the distribution of cyanate in the marine environment, 2) potential sources of cyanate and the timescales at which cyanate is produced, 3) the rate of cyanate removal via microbial uptake and spontaneous decomposition, and 4) the geochemical coupling between cyanate production and consumption. Results generated from this study will be important for augmenting knowledge of the marine nitrogen cycle, refining biogeochemical models, and further understanding of the functioning of marine microbial communities.