Sulphur compounds, methane, and phytoplankton: interactions along a north–south transit in the western Pacific Ocean

[摘要] Here we present results of the first comprehensive study of sulphur compoundsand methane in the oligotrophic tropical western Pacific Ocean. Theconcentrations of dimethylsuphide (DMS), dimethylsulphoniopropionate (DMSP),dimethylsulphoxide (DMSO), and methane (CH₄), as well as variousphytoplankton marker pigments in the surface ocean were measured along anorth–south transit from Japan to Australia in October 2009. DMS(0.9 nmol L⁻¹), dissolved DMSP (DMSP_d, 1.6 nmol L⁻¹)and particulate DMSP (DMSP_p, 2 nmol L⁻¹) concentrations weregenerally low, while dissolved DMSO (DMSO_d, 4.4 nmol L⁻¹)and particulate DMSO (DMSO_p, 11.5 nmol L⁻¹) concentrationswere comparably enhanced. Positive correlations were found between DMSO andDMSP as well as DMSP and DMSO with chlorophyll a, which suggests a similarsource for both compounds. Similar phytoplankton groups were identified asbeing important for the DMSO and DMSP pool, thus, the same algae taxa mightproduce both DMSP and DMSO. In contrast, phytoplankton seemed to play only aminor role for the DMS distribution in the western Pacific Ocean. Theobserved DMSP_p : DMSO_p ratios were very low and seem tobe characteristic of oligotrophic tropical waters representing the extremeendpoint of the global DMSP_p : DMSO_p ratio vs SSTrelationship. It is most likely that nutrient limitation and oxidative stressin the tropical western Pacific Ocean triggered enhanced DMSO production leadingto an accumulation of DMSO in the sea surface. Positive correlations betweenDMSP_d and CH₄, as well as between DMSO (particulate and total)and CH₄, were found along the transit. We conclude that DMSP and DMSOand/or their degradation products might serve as potential substrates forCH₄ production in the oxic surface layer of the western Pacific Ocean.

[学科分类] 地球化学与岩石