Dataset: Ammonia and Urea-derived-N Oxidation Rates
Deployment: N-SPOT_Yellowfin_Cruises

From 2014 to 2015, water samples were collected using a 12 x 12 L Niskin bottle rosette equipped with a conductivity, temperature, and density (CTD) instrument package (SBE 9plus, Sea-Bird Electronics, Bellevue, Washington, USA), including dissolved oxygen (SBE 43) and photosynthetically available radiation (PAR, LI-COR, Biospherical Instruments Inc., San Diego, California, USA) sensors. Due to CTD failure, samples collected in 2015 and 2016 were collected primarily using manually triggered Go-Flo bottles and depths were chosen primarily using a profiling natural fluorometer (PNF) system as well as secchi disk.

Rates of water column ammonia and urea-derived-N oxidation were measured from bottle incubations with ¹⁵NH₄Cl and ¹⁵N-urea (Dugdale and Goering 1967; Sigman et al. 2001; McIlvin and Casciotti 2011; Damashek et al. 2016). Isotope samples were analyzed using a Finnigan Delta Plus XP IRMS and Finnigan Delta Plus Advantage IRMS at the University of California Davis Stable Isotope Facility, the Central Appalachians Stable Isotope Facility at the University of Maryland Center for Environmental Science, and the Marine Science Institute Analytical Laboratory at the University of California, Santa Barbara.