New Production and Nitrogen-15 Uptake Rates Measured during the JGOFS Equatorial Pacific Process Study

During the fourth cruise (TT012), data were collected at 5 stations along 140 deg W longitude from 17 deg S latitude to the equator. During the first and third cruises, 6-8 depths were sampled per station with the cable/rosette system for nitrogen-uptake measurements. Standard autoanalyzer techniques were used to determine nitrogen concentrations of each sample.

Nitrogen-15 tracer was added to each sample at 10% of the ambient substrate concentration. The samples were incubated for 3-4 hours in simulated in situ conditions: subsurface light was approximated with a combination of neutral density and colored filters, and temperature was maintained +/- a few degrees C of the depth from which the sample was collected. Rates of nitrogen uptake were determined for labeled substrate of nitrate, nitrite and ammonium.

In addition, F-ratios were calculated as follows: f = pNO3/(pNO3+pNO2+pNH4), where pNO2 is the N-15 uptake rate from nitrite labeled substrate, pNO3 is the N-15 uptake rate from nitrate labeled substrate, and pNH4 is the N-15 uptake rate from ammonium labeled substrate. The data is public domain and can be retrieved on-line at "usjgofs.whoi.edu/jg/dir/jgofs/" [The information in this summary was taken from the JGOFS World Wide Web pages.]