Seawater carbonate chemistry, the abiotic conditions in the fluid surrounding the embryo, growth, calcification of the cuttlefish Sepia officinalis in a laboratory experiment

This study investigated the effects of seawater pH (i.e., 8.10, 7.85 and 7.60) and temperature (16 and 19 °C) on (a) the abiotic conditions in the fluid surrounding the embryo (viz. the perivitelline fluid), (b) growth, development and (c) cuttlebone calcification of embryonic and juvenile stages of the cephalopod Sepia officinalis. Egg swelling increased in response to acidification or warming, leading to an increase in egg surface while the interactive effects suggested a limited plasticity of the swelling modulation. Embryos experienced elevated pCO2 conditions in the perivitelline fluid (>3-fold higher pCO2 than that of ambient seawater), rendering the medium under-saturated even under ambient conditions. The growth of both embryos and juveniles was unaffected by pH, whereas 45Ca incorporation in cuttlebone increased significantly with decreasing pH at both temperatures. This phenomenon of hypercalcification is limited to only a number of animals but does not guarantee functional performance and calls for better mechanistic understanding of calcification processes.

Chemical and isotopic compositions of samples from the Haakon Mosby mud volcano and nearby

Authigenic carbonates in the caldera of an Arctic (72°N) submarine mud volcano with active methane-bearing fluid discharge are formed at the bottom surface during anaerobic microbial methane oxidation. The microbial community consists of specific methane-producing bacteria, which act as methanotrophic ones in conditions of excess methane, and sulfate reducers developing on hydrogen, which is an intermediate product of microbial CH4 oxidation. Isotopically light carbon (aver. d13C = -28.9 per mil) of CO2 produced during CH4 oxidation is the main carbonate carbon source. Heavy oxygen isotope ratio (aver. d18O = 5 per mil) in carbonates is inherited from seawater sulfate. Rapid sulfate reduction (up to 12 mg S/dm**3/day) results in total exhausting of sulfate ion in the upper sediment layer (10 cm). Because of this carbonates can only be formed in surface sediments near the water-bottom interface. Salinity as well as CO3/Ca and Mg/Ca ratios correspond to the field of non-magnesian calcium carbonate precipitation. Calcite is the dominant carbonate mineral in the methane seep caldera, where it occurs in the paragenetic association with barite. Radiocarbon age of carbonates is about 10 Ka.

(Figure 2) Suspended sediment concentration profiles from samples in the outer harbor of Emden, Germany

One particularly complex phenomenon is the episodic, tidally driven variation of navigable depth level as a result of fluid mud settlement. This paper presents results from dynamic cone penetration testing with pore pressure measurement (CPTU) as a nonacoustical, direct device to support surveying and management of these areas. The new technique is modular and uses a disk configuration for fluid mud detection. Both disk resistance and pore pressure measurements accurately identify suspended matter concentrations of 90 g/L or more, and the transition from fluid mud to consolidating mud once concentrations exceed 150 g/L. Hence, the procedure attests the potential for rapid, reliable assessment of a fluid mud layer and concurrent characterization of the underlying consolidated sediment by monitoring the pore pressure and strength changes during penetration.

Boron isotope ratios of samples from ODP Leg 125 sites at a serpentine seamount, Mariana forearc

Serpentinite clasts and muds erupted from Conical Seamount, Mariana forearc, show substantial enrichment in boron (B) and 11B (delta11B up to +15?) relative to mantle values. These elevated B isotope signatures result from chemical exchange with B-rich pore fluids that are upwelling through the seamount. If the trends of decreasing delta11B with slab depth shown by cross-arc magmatic suites in the Izu and Kurile arcs of the western Pacific are extended to shallow depths (~25 km), they intersect the inferred delta11B of the slab-derived fluids (+13x) at Conical Seamount. Simple mixtures of a B-rich fluid with a high delta11B and B-poor mantle with a low delta11B are insufficient to explain the combined forearc and arc data sets. The B isotope systematics of subduction-related rocks thus indicate that the fluids evolved from downgoing slabs are more enriched in 11B than the slab materials from which they originate. Progressively lower delta11B in arc lavas erupted above deep slabs reflects both the progressive depletion of 11B from the slab and progressively greater inputs of mantle-derived B. This suggests that the slab releases 11B-enriched fluids from the shallowest levels to depths greater than 200 km.