Geochemical characterization and the voltammetric investigation of hydrothermal Iron speciation of samples gained during SONNE cruise SO229

Hydrothermal vent fluids are highly enriched in iron (Fe) compared to ambient seawater, and organic ligands may play a role in facilitating the transport of some hydrothermal Fe into the open ocean. This is important since Fe is a limiting micronutrient for primary production in large parts of the world's surface ocean. We have investigated the concentration and speciation of Fe in several vent fluid and plume samples from the Nifonea vent field, Coriolis Troughs, New Hebrides Island Arc, South Pacific Ocean using competitive ligand exchange-adsorptive cathodic stripping voltammetry (CLE-AdCSV) with salicylaldoxime (SA) as the artificial ligand. Our results for total dissolved Fe (dFe) in the buoyant hydrothermal plume samples showed concentrations up to 3.86 µM dFe with only a small fraction between 1.1 and 11.8% being chemically labile. Iron binding ligand concentrations ([L]) were found in µM level with strong conditional stability constants up to logKFeL,Fe3+ of 22.9. Within the non-buoyant hydrothermal plume above the Nifonea vent field, up to 84.7% of the available Fe is chemically labile and [L] concentrations up to 97 nM were measured. [L] was consistently in excess of Felab, indicating that all available Fe is being complexed, which in combination with high Felab values in the non-buoyant plume, signifies that a high fraction of hydrothermal dFe is potentially being transported away from the plume into the surrounding waters, contributing to the global oceanic Fe budget.

Composition of organic matter from samples of massive sulfides, bottom sediments, and seawater collected within the Logachev and Broken Spur hydrothermal fields, Mid-Atlantic Ridge

Lipid components of hydrothermal deposits from the unusual field at 14°45'N MAR and from the typical field at 29°N MAR were studied. For the first time mixed nature of organic matter (OM) from hydrothermal sulfide deposits was established with use of biochemical, gas chromatographic, and molecular methods of studies. In composition of OM lipids of phytoplankton, those of chemosynthesis bacteria and non-biogenic synthesis lipids were determined. Specific conditions of localization of sulfide deposits originated from ''black smokers'' (reducing conditions, absence of free oxygen, presence of reduced sulfur preventing OM from decomposition) let biogenic material, including bacterial one, be preserved in sulfide deposits. The hydrothermal system at 14°45'N MAR is characterized by geological, geochemical and thermodynamic conditions allowing abiogenic synthesis of methane and petroleum hydrocarbons. For sulfide deposits at 29°N and other active hydrothermal fields known at MAR, abiogenic synthesis of hydrocarbons occurs in lower scales.

Composition of hydrothermal manifestations in the World Ocean

The monograph summarizes results of studies of hydrothermal fields on the ocean floor, hydrothermal plumes and metalliferous sediments. Hydrothermal ore manifestations formed in different geodynamic settings, with different character of volcanism in different facial conditions of deposition are described. Causes of non-uniformity of hydrothermal system functioning in different parts of the ocean and therefore variability of hydrothermal deposits are under consideration. On the base of found relationships of these irregularities with geodynamics, volcanism and sedimentation a new classification of hydrothermal processes and genetic models of hydrothermal ore formation in the ocean have been created. Regularities of hydrothermal sedimentary material dispersion in bottom waters are discussed.

(Table 1) Os and Sr isotopes in low-temperature hydrothermal fluids from the Juan de Fuca Ridge at ODP Site 168-1026B

We present Os and Sr isotopes and Mg, Os, and Sr concentrations for ridge-crest high-temperature and diffuse hydrothermal fluids, plume fluids and ridge-flank warm spring fluids from the Juan de Fuca Ridge. The data are used to evaluate the extent to which (1) the high- and low-temperature hydrothermal alteration of mid-ocean ridge basalts (MORBs) provides Os to the deep oceans, and (2) hydrothermal contributions of non-radiogenic Os and Sr to the oceans are coupled. The Os and Sr isotopic ratios of the high-temperature fluids (265-353°C) are dominated by basalts (187Os/188Os = 0.2; 87Sr/86Sr = 0.704) but the concentrations of these elements are buffered approximately at their seawater values. The 187Os/188Os of the hydrothermal plume fluids collected ~1 m above the orifice of Hulk vent is close to the seawater value (=1.05). The low-temperature diffuse fluids (10-40°C) associated with ridge-crest high-temperature hydrothermal systems on average have [Os] = 31 fmol/kg, 187Os/188Os = 0.9 and [Sr] = 86 µmol/kg, 87Sr/86Sr = 0.709. They appear to result from mixing of a high-temperature fluid and a seawater component. The ridge-flank warm spring fluids (10-62°C) on average yield [Os] = 22 fmol/kg, 187Os/188Os = 0.8 and [Sr] = 115 µmol/kg, 87Sr/86Sr = 0.708. The data are consistent with isotopic exchange of Os and Sr between basalt and circulating seawater during low-temperature hydrothermal alteration. The average Sr concentration in these fluids appears to be similar to seawater and consistent with previous studies. In comparison, the average Os concentration is less than seawater by more than a factor of two. If these data are representative they indicate that low-temperature alteration of MORB does not provide adequate non-radiogenic Os and that another source of mantle Os to the oceans must be investigated. At present, the magnitude of non-radiogenic Sr contribution via low-temperature seawater alteration is not well constrained. If non-radiogenic Sr to the oceans is predominantly from the alteration of MORB, our data suggest that there must be a different source of non-radiogenic Os and that the Os and Sr isotope systems in the oceans are decoupled.

Data compilation on the biological response to ocean acidification: environmental and experimental context of data sets and related literature

The exponential growth of studies on the biological response to ocean acidification over the last few decades has generated a large amount of data. To facilitate data comparison, a data compilation hosted at the data publisher PANGAEA was initiated in 2008 and is updated on a regular basis (doi:10.1594/PANGAEA.149999). By January 2015, a total of 581 data sets (over 4 000 000 data points) from 539 papers had been archived. Here we present the developments of this data compilation five years since its first description by Nisumaa et al. (2010). Most of study sites from which data archived are still in the Northern Hemisphere and the number of archived data from studies from the Southern Hemisphere and polar oceans are still relatively low. Data from 60 studies that investigated the response of a mix of organisms or natural communities were all added after 2010, indicating a welcomed shift from the study of individual organisms to communities and ecosystems. The initial imbalance of considerably more data archived on calcification and primary production than on other processes has improved. There is also a clear tendency towards more data archived from multifactorial studies after 2010. For easier and more effective access to ocean acidification data, the ocean acidification community is strongly encouraged to contribute to the data archiving effort, and help develop standard vocabularies describing the variables and define best practices for archiving ocean acidification data.