Reshaped new nitrogen regime by anticyclonic eddy in the Northern South China Sea
Description
Sampling was conducted in the northern South China Sea during July 2020, covering a spatial range of 113°E -118°E, 16°N-20°N. The data includes the nutrient concentrations (nitrate, nitrite, phosphate), dissolved organic nitrogen (DON) and particulate nitrogen (PN) concentrations, and the measurement of nitrogen isotope values. The stable nitrogen isotopic composition of nitrate + nitrite was analyzed using the "denitrifier" method for samples with [NO3-] > 0.5 μmol L-1 (Sigman et al. 2001). The content and isotopic composition of PN were analyzed on a Finnigan Delta V Advantage isotope ratio mass spectrometer interfaced with a Carlo Erba NC 2500 elemental analyzer (EA-IRMS). The detection limit for N content was 0.1 μmol N on the EA-IRMS. The concentration and δ15N of DON were measured by persulfate oxidation coupled with the denitrifying bacteria method (Zhang et al. 2020). The N2 fixation rate was measured via revised 15N2 bubble method (Klawonn et al. 2015; Li et al. 2023). The upward nitrate flux in the water column using high-resolution vertical profiles of nitrate concentration and the turbulent diffusion coefficient measured by shipborne Acoustic Doppler Current Profiler (ADCP).