Growth, DMS and DMSP production in Emiliania huxleyi under elevated CO_2 and UV radiation

摘要

The effects of ocean acidification and solar radiation on marine organisms have received increasing attention. Coccolithophores are a major producer of dimethylsulfoniopropionate (DMSP), which is a precursor of dimethylsulfide (DMS), a volatile biogenic active gas related to climate. Here, we investigated the individual and combined effects of elevated CO2 and ultraviolet radiation (UVR) on growth, DMS, and DMSP production of Emiliania huxleyi. Elevated CO2 (1000 mu atm, HC) decreased the cell concentration, DMS, and particulate DMSP (DMSPp) concentrations by 17, 20, and 13, respectively, compared with ambient CO2 (400 mu atm, LC) in the semi-continuous culture. The addition of UVA to photosynthetically active radiation (PAR) increased cell concentration of E. huxleyi by 16 on day 4, which may be due to the photorepair effects induced by UVA, and the effect was time-dependent. PAR + UVA and PAR + UVA + UVB exposure decreased cellular DMS by 25-56, and increased cellular DMSPp by 60-130 compared with PAR on days 3-4. Cellular DMSPp followed the order: PAR + UVA PAR + UVA + UVB PAR, and HC had no significant effects on cellular DMSPp compared with LC in the combined experiment. These results aid our understanding of the effects of ocean acidification and UV radiation on the production of methyl sulfur compounds in the ocean.