Description: Bio-optical and phytoplankton pigment measurements were carried out at several transatlantic ship cruises (Table 1) to validate satellite derived biogeochemical properties in open ocean waters. The remote sensing reflectances were determined from hyperspectral above and below water radiometric measurements using TriOS-RAMSES radiometers in open ocean waters and used to validate MERIS and MODIS remote sensing reflectance data. From water samples pigment composition and particulateabsorption were determined by HPLC (Hoffmann et al. 2006) and filter pad method (Tassan and Ferrari 1995), respectively. The phytoplankton pigment and bio-optical data from stations of the cruise ANT-XXV/1 (2008) were analyzed using a cluster-based approach proposed in Torrecilla et al., 2010 with the aim ofidentifying different phytoplankton assemblages and biooptical provinces in open ocean waters.

Description: Here we present results of the first comprehensive study of sulphur compounds and methane in the oligotrophic tropical western Pacific Ocean. The concentrations of dimethylsuphide (DMS), dimethylsulphoniopropionate (DMSP), dimethylsulphoxide (DMSO), and methane (CH4), as well as various phytoplankton marker pigments in the surface ocean were measured along a north–south transit from Japan to Australia in October 2009. DMS (0.9 nmol L−1), dissolved DMSP (DMSPd, 1.6 nmol L−1) and particulate DMSP (DMSPp, 2 nmol L−1) concentrations were generally low, while dissolved DMSO (DMSOd, 4.4 nmol L−1) and particulate DMSO (DMSOp, 11.5 nmol L−1) concentrations were comparably enhanced. Positive correlations were found between DMSO and DMSP as well as DMSP and DMSO with chlorophyll a, which suggests a similar source for both compounds. Similar phytoplankton groups were identified as being important for the DMSO and DMSP pool, thus, the same algae taxa might produce both DMSP and DMSO. In contrast, phytoplankton seemed to play only a minor role for the DMS distribution in the western Pacific Ocean. The observed DMSPp : DMSOp ratios were very low and seem to be characteristic of oligotrophic tropical waters representing the extreme endpoint of the global DMSPp : DMSOp ratio vs SST relationship. It is most likely that nutrient limitation and oxidative stress in the tropical western Pacific Ocean triggered enhanced DMSO production leading to an accumulation of DMSO in the sea surface. Positive correlations between DMSPd and CH4, as well as between DMSO (particulate and total) and CH4, were found along the transit. We conclude that DMSP and DMSO and/or their degradation products might serve as potential substrates for CH4 production in the oxic surface layer of the western Pacific Ocean.

Description: Here we present results of the first comprehensive study of sulphur compounds and methane in the oligotrophic tropical West Pacific Ocean. The concentrations of dimethylsuphide (DMS), dimethylsulphoniopropionate (DMSP), dimethylsulphoxide (DMSO), and methane (CH4), as well as various phytoplankton marker pigments in the surface ocean were measured along a north-south transit from Japan to Australia in October 2009. DMS (0.9 nmol l−1), dissolved DMSP (DMSPd, 1.6 nmol l−1) and particulate DMSP (DMSPp, 2 nmol l−1) concentrations were generally low, while dissolved DMSO (DMSOd, 4.4 nmol l−1) and particulate DMSO (DMSOp, 11.5 nmol l−1) concentrations were comparably enhanced. Positive correlations were found between DMSO and DMSP as well as DMSP and DMSO with chlorophyll a, which suggests a similar source for both compounds. Similar phytoplankton groups were identified as being important for the DMSO and DMSP pool, thus, the same algae taxa might produce both DMSP and DMSO. In contrast, phytoplankton seemed to play only a minor role for the DMS distribution in the western Pacific Ocean. The observed DMSPp : DMSOp ratios were very low and seem to be characteristic of oligotrophic tropical waters representing the extreme endpoint of the global DMSPp : DMSOp ratio vs. SST relationship. It is most likely that nutrient limitation and oxidative stress in the tropical West Pacific Ocean triggered enhanced DMSO production leading to an accumulation of DMSO in the sea surface. Positive correlations between DMSPd and CH4, as well as between DMSO (particulate and total) and CH4, were found along the transit. We conclude that both DMSP and DMSO serve as substrates for methanogenic bacteria in the western Pacific Ocean.