Dataset: Gulf of Mexico net primary production
Deployment: NF1704

Methodology: 

Net primary productivity (NPP) rates were measured at 6 depths spanning the euphotic zone (surface to deep chlorophyll maximum). Four incubation bottles (2.7 L) per depth were filled from Niskin rosettes (three light bottles, one dark bottle).  All bottles were spiked with H13CO3- (final concentration of 154 or 196 μmol L-1 on NF17 and NF18, respectively). Two light bottles were spiked with 15NO3- (final concentration of 10 or 8 nmol L-1 on NF17 and NF18, respectively) for nitrate uptake rate measurements.  Bottles were then incubated for 24 h on an in situ incubation array (Landry et al. 2009). Upon recovery, incubations were immediately vacuum filtered onto pre-combusted 25-mm GF/F filters in the dark. Filters were rinsed with filtered seawater, wrapped in foil and stored at  80°C. On land, samples were fumigated with HCl vapor to remove inorganic carbon, dried, and placed inside a tin cup for C/N and isotopic analysis at the UC Davis stable isotope facility. Because no statistically significant difference in H13CO3- uptake were detected between bottles spiked with 15NO3- and those without, NPP is reported as the average of the H13CO3- uptake in the three light bottles corrected for dark bottle H13CO3- uptake.  For additional details, see Yingling et al. (submitted). 

Sampling and Analytical Procedures:

Net primary productivity (NPP) rates were measured at 6 depths spanning the euphotic zone (surface to deep chlorophyll maximum). Four incubation bottles (2.7 L) per depth were filled from Niskin rosettes (three light bottles, one dark bottle).  All bottles were spiked with H13CO3- (final concentration of 154 or 196 μmol L-1 on NF17 and NF18, respectively). Two light bottles were spiked with 15NO3- (final concentration of 10 or 8 nmol L-1 on NF17 and NF18, respectively) for nitrate uptake rate measurements.  Bottles were then incubated for 24 h on an in situ incubation array (Landry et al. 2009). Upon recovery, incubations were immediately vacuum filtered onto pre-combusted 25-mm GF/F filters in the dark. Filters were rinsed with filtered seawater, wrapped in foil and stored at  80°C. On land, samples were fumigated with HCl vapor to remove inorganic carbon, dried, and placed inside a tin cup for C/N and isotopic analysis at the UC Davis stable isotope facility. Because no statistically significant difference in H13CO3- uptake were detected between bottles spiked with 15NO3- and those without, NPP is reported as the average of the H13CO3- uptake in the three light bottles corrected for dark bottle H13CO3- uptake.  For additional details, see Yingling et al. (submitted).