Total nitrogen, total organic carbon, stable nitrogen isotopes, amino acids and hexosamines in surface sediments from six stations in the South China Sea sampled during cruise of R/V SONNE 269

Surface sediment samples were collected in the South China Sea on the cruise of R/V SONNE 269 between August 6th and 20th 2019. The aim of the study was to investigate the impact of the Pearl River on sedimentary organic matter on the shelf and continental slope of the Pearl River mouth. Furthermore, amino acid and hexosamine contents and spectra are used to track resuspension processes on the shelf break. Samples were analysed for total nitrogen (N) and total carbon (TC) using a Carlo Erba nitrogen analyser 1500. Total organic carbon (TOC) was measured with the same instrument 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. 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 % of total AA 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 mononmers are presented in mol % of total HA and comprise glucosamine (GlcN) and galactosamine (GalN). 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, ox/anox and a detailed description of the methods can be found in Gaye et al. (2022, doi.org/10.5194/bg-19-807-2022).