(Table 1) Geochemical composition of surface waters obtained aboard the R/V Rift along the Volga-Caspian canal

The Volga River discharge consists of the waters transferred by fast currents through channels and the waters which are passing through the shallow areas of the delta overgrown by cane. Using the hydrochemical data, it is possible to track distribution of the waters modified by 'biofilters' of macrophytes in the delta shallows starting from the external edge of the delta. The main distinctive features of these waters are the high content of dissolved oxygen, the abnormally high values of the pH, and the low content of dissolved inorganic carbon (both total and as CO2). These waters extend in the shape of 1 to 3-km-wide strips at a distance of 20-40 km from the outer border of the delta. The analysis of the data obtained during the expeditions run by the Institute of Oceanology of the Russian Academy of Sciences in 2003-2009, along with archived and published data, show that such 'modified' waters occur almost constantly along the outer edge of the Volga River delta.

Physiological advantages of dwarfing in surviving extinctions in high-CO2 oceans

Excessive CO2 in the present-day ocean-atmosphere system is causing ocean acidification, and is likely to cause a severe biodiversity decline in the future, mirroring effects in many past mass extinctions. Fossil records demonstrate that organisms surviving such events were often smaller than those before, a phenomenon called the Lilliput effect. Here, we show that two gastropod species adapted to acidified seawater at shallow-water CO2 seeps were smaller than those found in normal pH conditions and had higher mass-specific energy consumption but significantly lower whole-animal metabolic energy demand. These physiological changes allowed the animals to maintain calcification and to partially repair shell dissolution. These observations of the long-term chronic effects of increased CO2 levels forewarn of changes we can expect in marine ecosystems as CO2 emissions continue to rise unchecked, and support the hypothesis that ocean acidification contributed to past extinction events. The ability to adapt through dwarfing can confer physiological advantages as the rate of CO2 emissions continues to increase.

Pore water chemistry of ODP Sites 201-1225, 201-1226 and 201-1231

High-resolution analyses of the oxygen isotope ratio (18O/16O) of dissolved sulfate in pore waters have been made to depths of >400 meters below seafloor (mbsf) at open-ocean and upwelling sites in the eastern equatorial Pacific Ocean. d18O values of dissolved sulfate (d18O-SO4) at the organic-poor open-ocean Site 1231 gave compositions close to modern seawater (+9.5 per mil vs. Vienna-standard mean ocean water, providing no chemical or isotopic evidence for microbial sulfate reduction (MSR). In contrast, the maximum d18O values at Sites 1225 and 1226, which contain higher organic matter contents, are +20 per mil and +28 per mil, respectively. Depth-correlative trends of increasing d18O-SO4, alkalinity, and ammonium and the presence of sulfide indicate significant oxidation of sedimentary organic matter by sulfate-reducing microbial populations at these sites. Although sulfate concentration profiles at Sites 1225 and 1231 both show similarly flat trends without significant net MSR, d18O-SO4 values at Site 1225 reveal the presence of significant microbial sulfur-cycling activity, which contrasts to Site 1231. This activity may include contributions from several processes, including enzyme-catalyzed equilibration between oxygen in sulfate and water superimposed upon bacterial sulfate reduction, which would tend to shift d18O-SO4 toward higher values than MSR alone, and sulfide oxidation, possibly coupled to reduction of Fe and Mn oxides and/or bacterial disproportionation of sulfur intermediates. Large isotope enrichment factors observed at Sites 1225 and 1226 (epsilon values between 42 per mil and 79 per mil) likely reflect concurrent processes of kinetic isotope fractionation, equilibrium fractionation between sulfate and water, and sulfide oxidation at low rates of sulfate reduction. The oxygen isotope ratio of dissolved pore water sulfate is a powerful tool for tracing microbial activity and sulfur cycling by the deep biosphere of deep-sea sediments.