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The Southern Ocean data base of dissolved barium (Bad) has been augmented with two densely sampled sections across the Weddell Gyre sampled by the icebreaker FS Polarstern during February and March 2005. Bad was found to be relatively high in the surface layer as compared to the adjacent waters north (Antarctic Circumpolar Current) and east (Antarctic Zone of the Indian sector). Compared to the inflowing water into the Weddell Gyre and also to the surface water, the deep water is characterized by a significant Ba-d enrichment. Depletion of Bad in the surface layer is associated with well-known biogeochemical processes, but we speculate that also sea-ice formation leads to the extraction of Ba from solution via barite (BaSO4) precipitation. The particulate Ba settles down the water column and redissolves in deeper water where undersaturation of barite is prevalent. In the bottom layer, enrichment of Ba-d occurs, exhibited as a Ba-d maximum, which is caused by Ba efflux from the sediments. In recently formed Weddell Sea Bottom Water, though, a Ba-d minimum is observed, imposed by the shelf water component of bottom water, which has relatively low Ba-d concentration. Like in other Southern Ocean regions, throughout the water column a strong correlation exists between Ba-d and dissolved silicate, although the relationship is different from that in the Antarctic regions to the east. In a tentative budget, the deep water is found to be supplied with Ba-d mainly by the surface layer, but also to some extent by the bottom layer. Weddell Sea Deep Water, enriched in Ba-d, is transferred out of the Weddell Gyre into the ACC as Antarctic Bottom Water, making the gyre a source of Ba-d to the deep and abyssal world oceans. (C) 2010 Elsevier B.V. All rights reserved.

The Southern Ocean data base of dissolved barium (Bad) has been augmented with two densely sampled sections across the Weddell Gyre sampled by the icebreaker FS Polarstern during February and March 2005. Bad was found to be relatively high in the surface layer as compared to the adjacent waters north (Antarctic Circumpolar Current) and east (Antarctic Zone of the Indian sector). Compared to the inflowing water into the Weddell Gyre and also to the surface water, the deep water is characterized by a significant Ba-d enrichment. Depletion of Bad in the surface layer is associated with well-known biogeochemical processes, but we speculate that also sea-ice formation leads to the extraction of Ba from solution via barite (BaSO4) precipitation. The particulate Ba settles down the water column and redissolves in deeper water where undersaturation of barite is prevalent. In the bottom layer, enrichment of Ba-d occurs, exhibited as a Ba-d maximum, which is caused by Ba efflux from the sediments. In recently formed Weddell Sea Bottom Water, though, a Ba-d minimum is observed, imposed by the shelf water component of bottom water, which has relatively low Ba-d concentration. Like in other Southern Ocean regions, throughout the water column a strong correlation exists between Ba-d and dissolved silicate, although the relationship is different from that in the Antarctic regions to the east. In a tentative budget, the deep water is found to be supplied with Ba-d mainly by the surface layer, but also to some extent by the bottom layer. Weddell Sea Deep Water, enriched in Ba-d, is transferred out of the Weddell Gyre into the ACC as Antarctic Bottom Water, making the gyre a source of Ba-d to the deep and abyssal world oceans. (C) 2010 Elsevier B.V. All rights reserved.

The influences of diet and seawater dissolved inorganic carbon (DIC) on the carbon isotope composition of shell aragonite (Cinched in the Manila clam Ruditapes philippinarum reared under laboratory conditions were investigated. Clams were exposed to two successive negative carbon isotope shifts: a first shift in diet (delta C-13(phytoplankton)) and a second shift, 35 days later, in DIC (delta C-13(DIC)). Both successive shifts induced a decrease in delta C-13(shell). These results are the first to experimentally confirm an incorporation of respired carbon derived from food and carbon from DIC into shell carbonate of adult bivalves. Skeletal delta C-13 responded to changes in the delta C-13 of both diet and DIC in less than 7 days. Consequently, proxies based on delta C-13(shell) may be used with high temporal resolution. Using delta C-13(phycoplankton) as a proxy for the carbon isotope composition of respired carbon (delta C-13(R)) resulted in a rather constant percentage of metabolic carbon (C-M) into the shell carbonate over time (close to 12%). However, an accurate estimation of delta C-13(R) is required in order to precisely estimate the percentage of metabolic carbon incorporated into the shell. Despite the significant incorporation of metabolic carbon into shell carbonate, our experimental results revealed that delta C-13(shell) was highly correlated with delta C-13(DIC) (r(2)=0.77, p<0.0001). Thus it seems that delta C-13(shell) is a promising proxy of large scale variations in delta C-13(DIC) and therefore of salinity in estuarine water. (C) 2010 Elsevier B.V. All rights reserved.

The Southern Ocean data base of dissolved barium (Bad) has been augmented with two densely sampled sections across the Weddell Gyre sampled by the icebreaker FS Polarstern during February and March 2005. Bad was found to be relatively high in the surface layer as compared to the adjacent waters north (Antarctic Circumpolar Current) and east (Antarctic Zone of the Indian sector). Compared to the inflowing water into the Weddell Gyre and also to the surface water, the deep water is characterized by a significant Ba-d enrichment. Depletion of Bad in the surface layer is associated with well-known biogeochemical processes, but we speculate that also sea-ice formation leads to the extraction of Ba from solution via barite (BaSO4) precipitation. The particulate Ba settles down the water column and redissolves in deeper water where undersaturation of barite is prevalent. In the bottom layer, enrichment of Ba-d occurs, exhibited as a Ba-d maximum, which is caused by Ba efflux from the sediments. In recently formed Weddell Sea Bottom Water, though, a Ba-d minimum is observed, imposed by the shelf water component of bottom water, which has relatively low Ba-d concentration. Like in other Southern Ocean regions, throughout the water column a strong correlation exists between Ba-d and dissolved silicate, although the relationship is different from that in the Antarctic regions to the east. In a tentative budget, the deep water is found to be supplied with Ba-d mainly by the surface layer, but also to some extent by the bottom layer. Weddell Sea Deep Water, enriched in Ba-d, is transferred out of the Weddell Gyre into the ACC as Antarctic Bottom Water, making the gyre a source of Ba-d to the deep and abyssal world oceans. (C) 2010 Elsevier B.V. All rights reserved.

The influences of diet and seawater dissolved inorganic carbon (DIC) on the carbon isotope composition of shell aragonite (Cinched in the Manila clam Ruditapes philippinarum reared under laboratory conditions were investigated. Clams were exposed to two successive negative carbon isotope shifts: a first shift in diet (delta C-13(phytoplankton)) and a second shift, 35 days later, in DIC (delta C-13(DIC)). Both successive shifts induced a decrease in delta C-13(shell). These results are the first to experimentally confirm an incorporation of respired carbon derived from food and carbon from DIC into shell carbonate of adult bivalves. Skeletal delta C-13 responded to changes in the delta C-13 of both diet and DIC in less than 7 days. Consequently, proxies based on delta C-13(shell) may be used with high temporal resolution. Using delta C-13(phycoplankton) as a proxy for the carbon isotope composition of respired carbon (delta C-13(R)) resulted in a rather constant percentage of metabolic carbon (C-M) into the shell carbonate over time (close to 12%). However, an accurate estimation of delta C-13(R) is required in order to precisely estimate the percentage of metabolic carbon incorporated into the shell. Despite the significant incorporation of metabolic carbon into shell carbonate, our experimental results revealed that delta C-13(shell) was highly correlated with delta C-13(DIC) (r(2)=0.77, p<0.0001). Thus it seems that delta C-13(shell) is a promising proxy of large scale variations in delta C-13(DIC) and therefore of salinity in estuarine water. (C) 2010 Elsevier B.V. All rights reserved.

The Southern Ocean data base of dissolved barium (Bad) has been augmented with two densely sampled sections across the Weddell Gyre sampled by the icebreaker FS Polarstern during February and March 2005. Bad was found to be relatively high in the surface layer as compared to the adjacent waters north (Antarctic Circumpolar Current) and east (Antarctic Zone of the Indian sector). Compared to the inflowing water into the Weddell Gyre and also to the surface water, the deep water is characterized by a significant Ba-d enrichment. Depletion of Bad in the surface layer is associated with well-known biogeochemical processes, but we speculate that also sea-ice formation leads to the extraction of Ba from solution via barite (BaSO4) precipitation. The particulate Ba settles down the water column and redissolves in deeper water where undersaturation of barite is prevalent. In the bottom layer, enrichment of Ba-d occurs, exhibited as a Ba-d maximum, which is caused by Ba efflux from the sediments. In recently formed Weddell Sea Bottom Water, though, a Ba-d minimum is observed, imposed by the shelf water component of bottom water, which has relatively low Ba-d concentration. Like in other Southern Ocean regions, throughout the water column a strong correlation exists between Ba-d and dissolved silicate, although the relationship is different from that in the Antarctic regions to the east. In a tentative budget, the deep water is found to be supplied with Ba-d mainly by the surface layer, but also to some extent by the bottom layer. Weddell Sea Deep Water, enriched in Ba-d, is transferred out of the Weddell Gyre into the ACC as Antarctic Bottom Water, making the gyre a source of Ba-d to the deep and abyssal world oceans. (C) 2010 Elsevier B.V. All rights reserved.

The influences of diet and seawater dissolved inorganic carbon (DIC) on the carbon isotope composition of shell aragonite (Cinched in the Manila clam Ruditapes philippinarum reared under laboratory conditions were investigated. Clams were exposed to two successive negative carbon isotope shifts: a first shift in diet (delta C-13(phytoplankton)) and a second shift, 35 days later, in DIC (delta C-13(DIC)). Both successive shifts induced a decrease in delta C-13(shell). These results are the first to experimentally confirm an incorporation of respired carbon derived from food and carbon from DIC into shell carbonate of adult bivalves. Skeletal delta C-13 responded to changes in the delta C-13 of both diet and DIC in less than 7 days. Consequently, proxies based on delta C-13(shell) may be used with high temporal resolution. Using delta C-13(phycoplankton) as a proxy for the carbon isotope composition of respired carbon (delta C-13(R)) resulted in a rather constant percentage of metabolic carbon (C-M) into the shell carbonate over time (close to 12%). However, an accurate estimation of delta C-13(R) is required in order to precisely estimate the percentage of metabolic carbon incorporated into the shell. Despite the significant incorporation of metabolic carbon into shell carbonate, our experimental results revealed that delta C-13(shell) was highly correlated with delta C-13(DIC) (r(2)=0.77, p<0.0001). Thus it seems that delta C-13(shell) is a promising proxy of large scale variations in delta C-13(DIC) and therefore of salinity in estuarine water. (C) 2010 Elsevier B.V. All rights reserved.

The first building blocks of life could be produced in ultramafic-hosted hydrothermal systems considering the large amounts of hydrogen and methane generated by serpentinisation and Fischer-Tropsch-Type synthesis, respectively, in those systems. The purpose of this study was to detect and characterise organic molecules in hydrothermal fluids from ultramafic-hosted hydrothermal systems in the Mid-Atlantic Ridge (MAR) region. During the EXOMAR cruise 2005, fluids from the Rainbow (36°14'N) and the Lost City (30°N) hydrothermal fields were collected and treated by Stir Bar Sorptive Extraction (SBSE) and Solid Phase Extraction (SPE). The extracts were analysed by Thermal Desorption-Gas Chromatography-Mass Spectrometry (TD-GC-MS) and GC-MS, respectively. Compared to nearby deep seawater, hydrothermal fluids were clearly enriched in organic compounds, with a more diverse spectrum of molecules. We observed a very similar range of organic compounds in fluids from both sites, with a dominance of aliphatic hydrocarbons (C9-C14), aromatic compounds (C6-C16) and carboxylic acids (C8-C18). The occurrence of these compounds is supported by other field studies on serpentinites and sulfide deposits. Literature on thermodynamic data and experimental work has suggested the possible abiogenic origin of hydrocarbons and organic acids. In addition, it has been shown elsewhere that catalytic reactions producing hydrocarbons likely occur at both Lost City and Rainbow hydrothermal fields as suggested by the evolution of [delta]13C with increasing C number for methane, ethane, propane and butane. In order to investigate the origin of the organic molecules in the fluids, compound-specific carbon isotope ratio measurements were performed on n-alkanes and carboxylic acids, for which the [delta]13C values were in the range of - 46 to - 20[per mille sign] (vs. V-PDB). These preliminary data did not allow conclusive support or rejection of an abiogenic origin of the compounds. Indeed, predicting

The first building blocks of life could be produced in ultramafic-hosted hydrothermal systems considering the large amounts of hydrogen and methane generated by serpentinisation and Fischer-Tropsch-Type synthesis, respectively, in those systems. The purpose of this study was to detect and characterise organic molecules in hydrothermal fluids from ultramafic-hosted hydrothermal systems in the Mid-Atlantic Ridge (MAR) region. During the EXOMAR cruise 2005, fluids from the Rainbow (36°14'N) and the Lost City (30°N) hydrothermal fields were collected and treated by Stir Bar Sorptive Extraction (SBSE) and Solid Phase Extraction (SPE). The extracts were analysed by Thermal Desorption-Gas Chromatography-Mass Spectrometry (TD-GC-MS) and GC-MS, respectively. Compared to nearby deep seawater, hydrothermal fluids were clearly enriched in organic compounds, with a more diverse spectrum of molecules. We observed a very similar range of organic compounds in fluids from both sites, with a dominance of aliphatic hydrocarbons (C9-C14), aromatic compounds (C6-C16) and carboxylic acids (C8-C18). The occurrence of these compounds is supported by other field studies on serpentinites and sulfide deposits. Literature on thermodynamic data and experimental work has suggested the possible abiogenic origin of hydrocarbons and organic acids. In addition, it has been shown elsewhere that catalytic reactions producing hydrocarbons likely occur at both Lost City and Rainbow hydrothermal fields as suggested by the evolution of [delta]13C with increasing C number for methane, ethane, propane and butane. In order to investigate the origin of the organic molecules in the fluids, compound-specific carbon isotope ratio measurements were performed on n-alkanes and carboxylic acids, for which the [delta]13C values were in the range of - 46 to - 20[per mille sign] (vs. V-PDB). These preliminary data did not allow conclusive support or rejection of an abiogenic origin of the compounds. Indeed, predicting

The first building blocks of life could be produced in ultramafic-hosted hydrothermal systems considering the large amounts of hydrogen and methane generated by serpentinisation and Fischer-Tropsch-Type synthesis, respectively, in those systems. The purpose of this study was to detect and characterise organic molecules in hydrothermal fluids from ultramafic-hosted hydrothermal systems in the Mid-Atlantic Ridge (MAR) region. During the EXOMAR cruise 2005, fluids from the Rainbow (36°14'N) and the Lost City (30°N) hydrothermal fields were collected and treated by Stir Bar Sorptive Extraction (SBSE) and Solid Phase Extraction (SPE). The extracts were analysed by Thermal Desorption-Gas Chromatography-Mass Spectrometry (TD-GC-MS) and GC-MS, respectively. Compared to nearby deep seawater, hydrothermal fluids were clearly enriched in organic compounds, with a more diverse spectrum of molecules. We observed a very similar range of organic compounds in fluids from both sites, with a dominance of aliphatic hydrocarbons (C9-C14), aromatic compounds (C6-C16) and carboxylic acids (C8-C18). The occurrence of these compounds is supported by other field studies on serpentinites and sulfide deposits. Literature on thermodynamic data and experimental work has suggested the possible abiogenic origin of hydrocarbons and organic acids. In addition, it has been shown elsewhere that catalytic reactions producing hydrocarbons likely occur at both Lost City and Rainbow hydrothermal fields as suggested by the evolution of [delta]13C with increasing C number for methane, ethane, propane and butane. In order to investigate the origin of the organic molecules in the fluids, compound-specific carbon isotope ratio measurements were performed on n-alkanes and carboxylic acids, for which the [delta]13C values were in the range of - 46 to - 20[per mille sign] (vs. V-PDB). These preliminary data did not allow conclusive support or rejection of an abiogenic origin of the compounds. Indeed, predicting

This study evaluates the possibilities and limitations of infrared laser ablation - inductively coupled plasma mass spectrometry, using Ca-43 as internal standard and the silicate glass reference materials NIST 610/612 as calibration standards, for quantifying the spatiotemporal variations of Mg, Mn, Sr, Ba and Pb in the calcite layer of Mytilus edulis shells. It demonstrates that the ablation behaviour of Ca relative to those of the analytes is dependent on the ablation time and substrate matrix (inorganic and biogenic calcite versus NIST 610/612); however, for ablation times less than or equal to 80 s, internal standardization with Ca improves precision to <10% relative standard deviation (RSD) for all tested substrates. Variations in the Ca distribution in the studied shells are shown to be comparable to this precision, implying that we can assume a constant Ca concentration. When using NIST 610/612 as calibration standards for the analysis of inorganic calcite, an accuracy better than 10% and a precision <8% RSD (not evaluated for Pb) are obtained for ablation times less than or equal to 40 s. For shell calcite a comparable reproducibility is obtained (<11% average difference between overlapping analysis series) but since no homogeneous shell reference material is available the accuracy cannot be determined. Experimental results indicate that for certain instrument operating conditions accuracy could be deteriorated by differences in ablation characteristics between samples and standards, so that matrix matching is preferable. Owing to the lack of a matrix matched standard for the analysis of shell calcite, we decided to use NIST 610/612 as standards and to assure intercomparability of our results by normalizing all data with respect to one selected shell. (C) 1999 Elsevier Science B.V. All rights reserved.