AbstractThe role of copepod Calanus sinicus on the production of dimethylsulfide (DMS)/dimethylsulfoniopropionate (DMSP) in Jiaozhou Bay was evaluated in field measurements and laboratory experiments. Samples at 10 sites in the bay were collected monthly from June 2010 to May 2011 (except for March 2011), and zooplankton species composition was analyzed. Effects of C. sinicus grazing on DMS/DMSP production at different conditions (i.e., algal diets, food concentrations, and salinities) were assessed in the laboratory. Data from the field experiment showed that C. sinicus was the dominant copepod in Jiaozhou Bay (up to 123 individuals/m3 in May 2011) and preferred to graze on diatom. DMS and DMSP concentrations depend on not only phytoplankton abundance but also phytoplankton species and bacterial abundance. In the laboratory experiment, compared with Gymnodinium sp. or Emiliania huxleyi, C. sinicus feeding on Isochrysis galbana and Chaetoceros curvisetus exhibited increased DMS concentration, whereas high salinity inhibited DMS production. Copepod ingested 0.5%–35% of DMSP in filtered phytoplankton, and copepod DMSP ingestion turnover rate in Jiaozhou Bay was up to 29 pmol L−1 d−1. Although the microbial DMSP consumption rate was 10–2,620‐fold of copepod turnover rate, copepod grazing was still one of the important routes in DMSP loss processes through food chain. This study indicated that DMSP was transferred from phytoplankton to copepod body, fecal pellet, and seawater through copepod grazing. Our results provided important information to understand the biogeochemical cycle of DMSP in Jiaozhou Bay.