Dataset: Event log and CTD/Niskin bottle data collected from R/V Endeavor cruise EN734 in the North Atlantic and Chesapeake Bay from Jul to Aug 2025

Event Log

The cruise track included six process stations, four of which comprised a transect along 36 N from the mid Sargasso Sea inshore towards Chesapeake Bay, including one in the Gulf Stream (PS1 - PS4). The other two stations (PS5, PS6) were inside Chesapeake Bay. Experimental manipulations to measure nitrogen (N) cycle processes were carried out at these stations. The sampling strategy was tailored to the process under investigation, e.g., photosynthesis and photochemical processes in surface waters, and depth profiles for most standard rates. Complete depth profiles were measured for nitrification, while CO₂ and nitrogen nutrient (nitrate, ammonium, urea) uptake rates focused on the euphotic zone. One additional short station (PS6) was sampled only for nitrification and nitrate uptake. Nitrous oxide consumption and photochemical production of nitrous oxide were measured in surface waters at PS1-PS5. 

CTD/Niskin bottle

A Seabird SBE-911+ was used with 12 30-L Niskin bottles. 

Sensors: 

1.     Temperature Sensor, SensorID="55"; serial number: 4695
2.     Conductivity Sensor, SensorID="3"; serial number: 0618
3.     Pressure, Digiquartz with TC, SensorID="45"; serial number: 0444
4.     Temperature Sensor, SensorID="55"; serial number: 4130
5.     Conductivity Sensor, SensorID="3"; serial number: 2822
6.     Transmissometer, WET Labs C-Star, SensorID="71"; serial number: 969DR
7.     Fluorometer, WET Labs ECO-AFL/FL, SensorID="20"; serial number: 4028
8.     Altimeter Sensor, SensorID="0"; serial number: 49898
9.     PAR/Irradiance, Biospherical/Licor, SensorID="42"; serial number: 70709
10.     Oxygen, SBE 43, SensorID="38"; serial number: 1230
11.     Oxygen, SBE 43, 2; SensorID="38"; serial number: 1648
12.     User Polynomial Sensor, SensorID="61"; serial number: 783
13.     SPAR, Biospherical/Licor, SensorID="51"; serial number: 20121