Seawater samples were collected monthly using a 5 L plexiglass water sampler from surface (<1 m) and subsurface (~1 m above bottom) layers at 14 study sites in Jiaozhou Bay during September 2016 and August 2017. Seawater NMHCs concentrations were measured with a customized purge and trap preconcentration setup coupled to a gas chromatography-mass spectrometer.Jiaozhou_Bay_2016-2017.

Analysis methods： Temperature，salinity was measured by CTD probe (SBE 38). Nutrients were determined with an AA3 nutrients analyzer (SEAL Analytical, UK). For Chl-a analysis, ~300 ml seawater was filtered through an 0.7 μm Whatman GF/F filter to collect phytoplankton biomass. The filters were soaked in 90% acetone solution for 24 hours and then centrifuged for 10 min at 4000 rpm. The supernatant was analyzed with a fluorescence spectrophotometer (Hitachi F-4500). DOC was determined using the high-temperature catalytic oxidation method by non-dispersive infrared gas analyzer (Shimadzu TOC-142 VCPH, Shimadzu Co., Japan).* Seawater NMHCs concentrations were measured with a customized purge and trap preconcentration setup coupled to a gas chromatography-mass spectrometer (GC-MS,Agilent 7890N/5973N, USA).