Total nitrogen, total organic carbon, stable nitrogen isotopes, amino acids and hexosamines in suspended matter samples from the South China Sea collected on cruise of R/C SONNE 269

This set of suspended matter (SPM) samples and water samples were collected in the South China Sea on the cruise of R/V SONNE 269 between August 5th and 31st 2019. The aim of this study was to better understand sources and cycling processes of SPM (i) in a region influenced by a river draining a so-called megacity and (ii) at the shelf break. Samples were analysed for total nitrogen (N) and total organic carbon carbon (TOC) using a Carlo Erba nitrogen analyser 1500 after treatment of weighed samples with 1N HCl to remove carbonate. Stable nitrogen isotopes of total particulate nitrogen (δ15N-TPN) were analysed with the mass spectrometer Thermo Finnigan MAT 252. Stable nitrogen and oxygen isotopes of nitrate (δ15N-NO3, δ18O-NO3) were analysed by the denitrifier method with a Delta Plus XP mass spectrometer. AA and HA contents and their individual monomers were analysed by liquid chromatography using a Biochrom 30 amino acid analyzer. Contents of AA and HA are presented in µmol/g and µg/g. AAC, AAN, HAC, HAN are presented in µg/g and as percentages of TOC (AAC/C, HAC/C) or TN (AAN/N, HAN/N). AA monomers are presented in mol % and comprise cysteic acid (CYA), taurine (TAU), methionine sulfoximine (MSO), aspartic acid (ASP), glutamic acid (Glu), threonine (Thr), serine (Ser), glycine (Gly), alanine (Ala), valine (Val), methionine (Met), isoleucine (Ile), leucine (Leu), tyrosine (Tyr), phenylalanine (Phe), β-Alanine (β-Ala), γ-aminobutyric acid (γ-Aba), histidine (His), tryptophane (TRP), ornithine (Orn), lysine (Lys) and arginine (Arg). HA monomers are present in mol % of total HA and comprise glucosamine (GlcN) and galactosamine (GalN). Data gaps indicate that measurements were not carried out. The RI was calculated according to Jennerjahn and Ittekkot (1997; https://archimer.ifremer.fr/doc/00093/20403/) and the DI after Dauwe et al. (1999; doi:10.4319/lo.1999.44.7.1809). Definitions of biogeochemical indicators SDI, RTI and a detailed description of the methods can be found in Gaye et al. (2022; doi.org/10.5194/bg-19-807-2022).