Fossil decapods from the Upper Quaternary in Shinjima Island in Kagoshima, Kyushu, Japan, and description of a new species of ghost shrimp (Axiidea, Eucalliacidae).

Five species of decapod crustaceans, including Calliax nishiki sp. nov. (Axiidea, Eucalliacidae) and Carcinoplax longimana (de Haan), are described from the upper part of the Moeshima Silt Bed (latest Pleistocene to Holocene: ca 13,000 to 8,000 cal BP). Ten decapods, including Laticallichirus grandis (Karasawa Goda) and Ebalia tuberculosa (A. Milne-Edwards) are described from the Moeshima Shell Bed (Holocene: ca 8,000 to 2,000 cal BP). Calliax nishiki is abundant and Carcinoplax longimana is common in the decapod assemblage of Moeshima Silt Bed. The new species of Calliax seems to have dispersed around the deep marine setting with a reducing environment. The decapod assemblage of the Moeshima Shell Bed is characterized by a predominance of L. grandis. The present record suggests that L. grandis is abundant under sandy and gravelly bottoms mixed with shells of the lower sublittoral to subtidal zones during the Quaternary.

Ice Melting Can Change DMSP Production and Photosynthetic Activity of the Haptophyte Phaeocystis antarctica1.

Phaeocystis antarctica is an important primary producer in the Southern Ocean and plays roles in sulfur cycles through intracellular production of dimethylsulfoniopropionate (DMSP), a principal precursor of dimethyl sulfide (DMS). Haptophytes, including P. antarctica, are known to produce more DMSP than other phytoplankton groups such as diatoms and green algae, suggesting their important contribution to DMS concentrations in the Southern Ocean. We assessed how sea ice formation and melting affect photosynthesis and DMSP accumulation in P. antarctica both in seawater and in sea ice. Incubations were undertaken in an ice tank, which simulated sea ice formation and melting dynamics. The maximum quantum yield of photochemistry (Fv /Fm ) in photosystem II, as estimated from pulse-amplitude-modulated (PAM) fluorometry, was generally higher under low-light conditions than high-light conditions. Values of Fv /Fm , the relative maximum electron rate (rETRmax ), and photosynthetic efficiency (α) were lower in sea ice than in seawater, implying reduced photosynthetic function inside the sea ice. The reduction in photosynthetic function was probably due to the hypersaline environment in the brine channels. Total DMSP (DMSPt) concentration normalized by chlorophyll-a concentration was significantly higher in the sea ice than in the other environments, suggesting high accumulation of DMSP, probably due to its osmotic properties. Fv /Fm , specific growth rate, and DMSPt concentrations decreased with decreasing salinity with the lowest values found at a salinity of 22, that is, the lowest salinity tested. These results suggest that sea ice melting is responsible for a reduction in growth rate and DMSP production of P. antarctica.

Abundance and distribution of dimethylsulfoniopropionate degradation genes and the corresponding bacterial community structure at dimethyl sulfide hot spots in the tropical and subtropical pacific ocean.

Dimethylsulfoniopropionate (DMSP) is mainly produced by marine phytoplankton but is released into the microbial food web and degraded by marine bacteria to dimethyl sulfide (DMS) and other products. To reveal the abundance and distribution of bacterial DMSP degradation genes and the corresponding bacterial communities in relation to DMS and DMSP concentrations in seawater, we collected surface seawater samples from DMS hot spot sites during a cruise across the Pacific Ocean. We analyzed the genes encoding DMSP lyase (dddP) and DMSP demethylase (dmdA), which are responsible for the transformation of DMSP to DMS and DMSP assimilation, respectively. The averaged abundance (±standard deviation) of these DMSP degradation genes relative to that of the 16S rRNA genes was 33% ± 12%. The abundances of these genes showed large spatial variations. dddP genes showed more variation in abundances than dmdA genes. Multidimensional analysis based on the abundances of DMSP degradation genes and environmental factors revealed that the distribution pattern of these genes was influenced by chlorophyll a concentrations and temperatures. dddP genes, dmdA subclade C/2 genes, and dmdA subclade D genes exhibited significant correlations with the marine Roseobacter clade, SAR11 subgroup Ib, and SAR11 subgroup Ia, respectively. SAR11 subgroups Ia and Ib, which possessed dmdA genes, were suggested to be the main potential DMSP consumers. The Roseobacter clade members possessing dddP genes in oligotrophic subtropical regions were possible DMS producers. These results suggest that DMSP degradation genes are abundant and widely distributed in the surface seawater and that the marine bacteria possessing these genes influence the degradation of DMSP and regulate the emissions of DMS in subtropical gyres of the Pacific Ocean.

Measurement of air-sea exchange of dimethyl sulfide and acetone by PTR-MS coupled with gradient flux technique.

We developed a new method for in situ measurement of air-sea fluxes of multiple volatile organic compounds (VOCs) by combining proton transfer reaction-mass spectrometry (PTR-MS) and gradient flux (GF) technique. The PTR-MS/GF system was first deployed to determine the air-sea flux of VOCs in the open ocean of the western Pacific, in addition to carbon dioxide and water vapor. Each profiling at seven heights from the ocean surface up to 14 m took 7 min. In total, 34 vertical profiles of VOCs in the marine atmosphere just above the ocean surface were obtained. The vertical gradient observed was significant for dimethyl sulfide (DMS) and acetone with the best-fit curves on quasi-logarithmic relationship. The mean fluxes of DMS and acetone were 5.5 ± 1.5 and 2.7 ± 1.3 µmol/m(2)/day, respectively. These fluxes are in general in accordance with those reported by previous expeditions.

Equilibrator inlet-proton transfer reaction-mass spectrometry (EI-PTR-MS) for sensitive, high-resolution measurement of dimethyl sulfide dissolved in seawater.

We developed an equilibrator inlet-proton transfer reaction-mass spectrometry (EI-PTR-MS) method for fast detection of dimethyl sulfide (DMS) dissolved in seawater. Dissolved DMS extracted by bubbling pure nitrogen through the sample was continuously directed to the PTR-MS instrument. The equilibration of DMS between seawater and the carrier gas, and the response time of the system, were evaluated in the laboratory. DMS reached equilibrium with an overall response time of 1 min. The detection limit (50 pmol L(-1) at 5 s integration) was sufficient for detection of DMS concentrations in the open ocean. The EI-PTR-MS instrument was deployed during a research cruise in the western North Pacific Ocean. Comparison of the EI-PTR-MS results with results obtained by means of membrane tube equilibrator-gas chromatography/mass spectrometry agreed reasonably well on average (R(2) = 0.99). EI-PTR-MS captured temporal variations of dissolved DMS concentrations, including elevated peaks associated with patches of high biogenic activity. These results demonstrate that the EI-PTR-MS technique was effective for highly time-resolved measurements of DMS in the open ocean. Further measurements will improve our understanding of the biogeochemical mechanisms of the production, consumption, and distribution of DMS on the ocean surface and, hence, the air-sea flux of DMS, which is a climatically important species.