Table of Contents

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

CTD profiles were collected using a Sea-Bird CTD system deployed from the research vessel during the SPOT cruise. The dataset includes two CTD casts conducted on February 19, 2025, which are distinguished using a Cast_ID column. The instrument was stabilized near the surface (0–5 m) prior to profiling and then lowered through the water column at a controlled rate of approximately 10–40 m min⁻¹. Sensor data were recorded continuously during the downcast, and discrete water samples were collected during the upcast using Niskin bottles mounted on the rosette.

The CTD system consisted of a Sea-Bird Electronics SBE 9plus equipped with sensors for pressure, temperature (SBE 3), conductivity (SBE 4C), and dissolved oxygen (SBE 43), as well as auxiliary sensors including photosynthetically active radiation (PAR), chlorophyll fluorescence (WET Labs ECO-AFL), turbidity, and beam transmission (C-Star transmissometer). Sensors were regularly calibrated by the manufacturer to ensure data accuracy.

CTD data were acquired at high frequency (24 Hz) using Sea-Bird software (Seasoft/Seasave) and processed using standard Sea-Bird protocols. Raw data files (.hex) and associated configuration files were used to generate processed profile data, including derived variables such as salinity from conductivity and temperature. Bottle data were matched to CTD profiles using time and depth records.

This section documents curation actions performed prior to publication review with the submitter, and additional information relevant to understanding and reusing this dataset. It distinguishes changes made to the submitted (meta)data from unresolved issues and/or enhancements that improve future reuse and interoperability.

CURATION ACTIONS PERFORMED ON DATA

- Loaded Cast_1 data from Sheet1 of SPOT_CTD_20250219.xlsx, with header on row 1, applying floating point error adjustment and preserved formatting; empty strings and "nd" set as missing values
- Loaded Cast_2 data from Sheet2 of the same file, which lacked Date_of_sampling, Latitude, Longitude, and Cast_ID columns; noted that its Flag column was stored in scientific notation (e.g. 0.00E+00); same missing value and formatting settings applied
- Added constant column Date_of_sampling ("2025-02-19") from sheet1 to all sheet2 rows, constant column Latitude (33.55) from sheet1 to all sheet2 rows via math operation, constant column Longitude (-118.4) from sheet1 to all sheet2 rows via math operation, and constant column Cast_ID ("Cast_2") to all sheet2 rows, which represent data from the second cast
- Concatenated sheet1 and sheet2 into a single table named combined_ctd, mapping matching columns (C0S/m, CStarTr0, Cast_ID, Date_of_sampling, DepSM, FlECO-AFL, Flag, Latitude, Longitude, Par/sat/log, Ph, PrdE, Sal00, Sbeox0Mg/L, Sbeox0PS, T090C, TimeS, TurbWETntu0)
- Renamed columns based on BCO-DMO conventions: T090C to Temp, C0S/m to Conductivity, Sal00 to Salinity, PrdE to Pressure, Sbeox0Mg/L to Oxygen_mg_l, Sbeox0PS to Oxygen_percent_sat, Par/sat/log to PAR, FlECO-AFL to Fluorescence, TurbWETntu0 to Turbidity, CStarTr0 to Beam_transmission, TimeS to Elapsed_time, DepSM to Depth
- Set Flag column to number type first to correctly parse scientific-notation values (e.g. 0.00E+00) originating from sheet2
- Rounded Flag to zero decimal places without preserving trailing zeros, converting it to integer type, resolving the scientific-notation casting issue
- Output as 1005588_v1_spot_ctd_20250219.csv

CURATION ACTIONS PERFORMED ON METADATA

- Used context from methods section to provide more detail for parameter descriptions

ISSUES POTENTIALLY IMPACTING REUSE

- N/A

NSF Award Abstract:

This project seeks to provide a deeper understanding of how major biogeochemical cycles that support all living marine resources will respond to climate warming in a changing ocean environment. It will train one postdoctoral researcher and three graduate students, and provides research training opportunities for undergraduate students in microbial physiology and ecology, bioinformatics, trace metal biogeochemistry, and oceanography. Project personnel also conduct K-12 education and outreach activities. All data is freely available through the Biological and Chemical Oceanographic Data Management Office (BCO-DMO).

This project investigates how climate warming will interact with the unique trace metal requirements of marine nitrifying microorganisms (nitrifiers) to affect ammonia and nitrite oxidation pathways in the rapidly changing ocean. Four investigators with diverse expertise in microbial global change physiology, nitrogen and trace metal biogeochemistry, and mechanistic transcriptomics and proteomics combine their efforts, using well-controlled pure culture-based laboratory studies along with field incubation experiments with natural communities to systematically investigate 1) thermal effects on iron (Fe) and copper (Cu) requirements and use efficiencies in isolated cultures and natural populations of marine ammonia-oxidizing archaea and bacteria (AOA, AOB) and nitrite-oxidizing bacteria (NOB), 2) the underlying molecular and biochemical mechanisms that facilitate such thermally-driven adaptive responses, and 3) system-level feedbacks between global change, trace metal biogeochemistry, and marine nitrifiers and their associated microbial communities in diverse marine environments. Together, these studies enhance our understanding of the marine nitrogen cycle and trace metal biogeochemistry, and ultimately contribute to a more detailed understanding of the impact of rapid ocean warming on critical major nutrient and micronutrient cycles.

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.