Data for: Land-based dissolved organic nitrogen dynamics and bioavailability in Jiaozhou Bay, China

TDN and DOC were determined by a TOC/TN auto-analyzer (Multi N/C 3100, Jena, Germany) through high-temperature catalytic oxidation (Vance et al., 1989). DIN (including NH4+, NO3-, and NO2-) was determined by autonomous nutrient analyzer (Bran-Lubbe AAⅢ，Germany) through spectrophotometry (Strickland and Parsons, 1972). DON was calculated as the difference between TDN and DIN. An ultraviolet visible spectrophotometer (Shimadzu UV-2550, Japan) was used for the determination of SUVA254. SUVA254 was calculated using the decadic light absorption coefficient at 254 nm (1/m) normalized to DOC (mgC/L) and used as a proxy for aromaticity (Weishaar et al., 2003). The emission–excitation matrix (EEM) spectra for FDOM were determined using a Fluorolog-3 fluorescence spectrophotometer (F4500, France) and a one-centimeter acid-washed quartz cuvette (Spencer et al. 2007). The fluorescence spectra were Raman calibrated by normalizing to the area under the Raman scatter peak (excitation wavelength of 350 nm) of a Milli-Q water sample in Raman units (R.U., nm-1) (Stedmon et al., 2003). The humification index (HIX) was calculated by the ratio of the peak area under the Em spectra 435-480 nm divided by 300-345 nm, at Ex 254 nm (Fellman et al., 2010).