(Table 3, page 373) Chemical composition of manganese nodules from the Komahashi-Daini Seamount in the Northern Philippine Sea

Petrological, mineralogical and chemical investigations of marine manganese nodules from the West Pacific revealed the intimate relation between the chemical and mineral compositions and the remarkable preferential partitioning of metal elements in the ferromanganese minerals. The microscopic observations of textures of manganese nodules tell the growth history of manganese nodules and the formation conditions of ferromanganese minerals. Chemical compositions of nodules from Komahashi-Daini Seamount are very similar to those of the nodules from marginal banks and seamounts. Compositional variations in the bulk composition of nodules collected from the same dredge haul are considerably small, suggesting the similarity of the growth history of individual nodules, although the contents of metal elements vary remarkably from layer to layer in a single nodule.

Ocean acidification slows nitrogen fixation and growth in the dominant diazotroph Trichodesmium under low-iron conditions

Dissolution of anthropogenic CO(2) increases the partial pressure of CO(2) (pCO(2)) and decreases the pH of seawater. The rate of Fe uptake by the dominant N(2)-fixing cyanobacterium Trichodesmium declines as pH decreases in metal-buffered medium. The slower Fe-uptake rate at low pH results from changes in Fe chemistry and not from a physiological response of the organism. Contrary to previous observations in nutrient-replete media, increasing pCO(2)/decreasing pH causes a decrease in the rates of N(2) fixation and growth in Trichodesmium under low-Fe conditions. This result was obtained even though the bioavailability of Fe was maintained at a constant level by increasing the total Fe concentration at low pH. Short-term experiments in which pCO(2) and pH were varied independently showed that the decrease in N(2) fixation is caused by decreasing pH rather than by increasing pCO(2) and corresponds to a lower efficiency of the nitrogenase enzyme. To compensate partially for the loss of N(2) fixation efficiency at low pH, Trichodesmium synthesizes additional nitrogenase. This increase comes partly at the cost of down-regulation of Fe-containing photosynthetic proteins. Our results show that although increasing pCO(2) often is beneficial to photosynthetic marine organisms, the concurrent decreasing pH can affect primary producers negatively. Such negative effects can occur both through chemical mechanisms, such as the bioavailability of key nutrients like Fe, and through biological mechanisms, as shown by the decrease in N(2) fixation in Fe-limited Trichodesmium.

Geochemistry of lower and middle Keuper sediments in the Central Thuringian Syncline

Cuttings of Lower and Middle Keuper sediments of the INFLUINS-drilling in the central Thuringian Syncline were geochemically analysed. Indications about shifting depositional environments are interpreted from ratios of whole-rock element contents. For the middle part of sandstone cycle S 2 high heavy metal contents imply precipitation of sufidic ores during a short marine interval. Element contents are compared with potential source rocks in the southern part of the Baltic Shield, in the Lausitz Anticline Zone, in the Erzgebirge, in the moldanubian part, in the broad sense, of the Bohemian Massif, in the Münchberg Gneiss Massif and the Fichtelgebirge. The geochemical coincidence of investigated Keuper sediments is highest with grantioid and gabbroic rocks of southern Scandinavia. Granodiorite rocks of the Lausitz are also possible sources, whereas granites of the Fichtelgebirge and the Bohemian Massif are less probable.

Chemical composition of nodules from two locations in the Pacific Ocean using different methods

Manganese nodules recovered in the Pacific Ocean by the U. S. Bureau of Mines and by DeepSea Ventures Ltd. are studied for their chemical composition using X microprobe and X-ray fluorescence methods.

(Table II, page 668-669) Distribution of elements between minerals soluble in 1M Hydroxylamine hydrochloride (Reducible); in 1m HCL (Acid-soluble) and in the insoluble residue of manganese nodules

Attempts to classify pelagic sediments have been based either on appearance and composition, or on the ultimate origin of the components. In particular it appears feasible to distinguish minerals which crystallized in sea-water from those which formed in magmas, in hydrothermal solution, or by weathering under acidic conditions. It is the case of iron and manganese oxide mineral aggregates which constitute one of the major types of rock encountered on the ocean floor; according to Menard (unpublished) about 10% of the pelagic area of the Pacific is covered by such nodules. The nodules consist of intimately intergrown crystallites of different minerals among those identified, besides detrital minerals and organic matter, are opal, goethite, rutile, anatase, barite, nontronite, and at least three manganese oxide minerals of major importance. Arrhenius and Korkisch (1959) have attempted to separate from each other the different minerals constituting the nodules, in order to establish the details of their structure and the localization of the heavy metal ions. The results demonstrate (Table II) that copper and nickel are concentrated in the manganese oxide phases concentrated in the reducible fraction. Cobalt, part of the nickel and most of the chromium are distributed between these and the acid-soluble group of the non-manganese minerals, dominated by goethite and disordered FeOOH.

Annotated record of the detailed examination of Mn deposits from R/V Xiang Yang Hong 16 stations (1983) in the Pacific Ocean

Electron microprobe and X-ray diffraction data for north Pacific manganese nodules reveal that the transition metal distributions are controlled by the mineralogy. Microlayers rich in 10Å-manganates generally have high Mn/Fe ratios and positive correlations between Ni, Cu and Mn, and between Co and Fe. Microlayers rich in vernadite, on the other hand, show low Mn/Fe ratios, and Co, Ni and Cu all show positive correlations with Mn. The 10Å-manganates form mainly in porewaters with high Mn/Fe ratios. The Ni2+ and Cu2+ ions are post-depositionally incorporated into the interlayers of the manganates, whereas Co3+ is substituted for Fe3+ in ferric oxyhydroxides. In seawater with a low Mn/Fe ratio, on the other hand, the adsorption of positively charged ferric oxyhydroxides on negatively charged [MnO6] octahedral layers suppresses the growth of 10Å-manganates, enhancing the formation of vernadite. Positively charged hydroxides of Co3+, Ni2+ and Cu2+ are also adsorbed on the [MnO6] layers. These mechanisms of mineral formation and metal uptake are corroborated by data for other oceanic non-hydrothermal manganese nodules and crusts.

(Table 3, Page 417) Table 3. The concentrations of Zn, Cu, Pb, Cd, Ni, Co, Ag, Mn and Fe in a soluble in 1M HCl fraction of ferromanganese nodules of Slupsk Furrow in the southern Baltic sea

The concentration of Zn, Cu, Pb, Cd, Ni, Co, Ag, Mn, Fe, Ca, Mg, K and Na in molluscs Macoma balthica, Mya arenaria, Cardium glaucum, Mytilus edulis and Astarte borealis from the southern Baltic was determined. The surface sediments and ferromanganese concretions associated with the molluscs were also analysed for concentration of these metals. Species- and region-dependent differences in the metal levels of the organisms were observed. The properties of molluscs analysed which have a tendency toward elevated biological tolerance of selected trace metals were specified. The interelement relationship between metal concentrations in the soft tissue and the shell was estimated and was discussed.

Geochemical analysis at ODP Site 207-1261 from the Demerara Rise in the western equatorial Atlantic

A high-resolution geochemical record of a 120 cm black shale interval deposited during the Coniacian-Santonian Oceanic Anoxic Event 3 (ODP Leg 207, Site 1261, Demerara Rise) has been constructed to provide detailed insight into rapid changes in deep ocean and sediment paleo-redox conditions. High contents of organic matter, sulfur and redox-sensitive trace metals (Cd, Mo, V, Zn), as well as continuous lamination, point to deposition under consistently oxygen-free and largely sulfidic bottom water conditions. However, rapid and cyclic changes in deep ocean redox are documented by short-term (~15-20 ka) intervals with decreased total organic carbon (TOC), S and redox-sensitive trace metal contents, and in particular pronounced phosphorus peaks (up to 2.5 wt% P) associated with elevated Fe oxide contents. Sequential iron and phosphate extractions confirm that P is dominantly bound to iron oxides and incorporated into authigenic apatite. Preservation of this Fe-P coupling in an otherwise sulfidic depositional environment (as indicated by Fe speciation and high amounts of sulfurized organic matter) may be unexpected, and provides evidence for temporarily non-sulfidic bottom waters. However, there is no evidence for deposition under oxic conditions. Instead, sulfidic conditions were punctuated by periods of anoxic, non-sulfidic bottom waters. During these periods, phosphate was effectively scavenged during precipitation of iron (oxyhydr)oxides in the upper water column, and was subsequently deposited and largely preserved at the sea floor. After ~15-25 ka, sulfidic bottom water conditions were re-established, leading to the initial precipitation of CdS, ZnS and pyrite. Subsequently, increasing concentrations of H2S in the water column led to extensive formation of sulfurized organic matter, which effectively scavenged particle-reactive Mo complexes (thiomolybdates). At Site 1261, sulfidic bottom waters lasted for ?90-100 ka, followed by another period of anoxic, non-sulfidic conditions lasting for ~15-20 ka. The observed cyclicity at the lower end of the redox scale may have been triggered by repeated incursions of more oxygenated surface- to mid-waters from the South Atlantic resulting in a lowering of the oxic-anoxic chemocline in the water column. Alternatively, sea water sulfate might have been stripped by long-lasting high rates of sulfate reduction, removing the ultimate source for HS**- production.