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Abstract: We investigated interactions between geochemical reference samples and CO2-saturagted seawater. The experiments were made under normal temperature and atmospheric pressure. We used the reference samples of igneous rocks, sedimentary rocks, sediments and terrestrial soil, issued from the Geological Survey of Japan (AIST). Chemical parameters in the seawater reacted with rock/sediment samples were determined. The results of quantitative analysis of by ICP-AES showed that calcium was released from coral, dolomite and limestone due to the dissolution of calcium carbonate in seawater acidified by CO2. Significant changes of other elements were not detected for all samples. The results of nutrient analysis showed that phosphate was eluted from dolomite, slate, coastal marine sediment and pelagic marine sediment significantly. Significant concentration of nitrate and nitrite were not detected except in the seawater reacted with terrestrial soil. On the other hand, concentrations of ammonia increased in the seawater reacted with slate, coastal marine sediment, pelagic marine sediment and terrestrial soil. Dissolved inorganic carbon (DIC) and total alkalinity (TA) were clearly increased in the seawater reacted with coral, dolomite, limestone. As above, increases of calcium were also detected in these samples, suggesting dissolution of calcium carbonate to the seawater acidified by CO2. Increase of DIC and TA in the coral sample are corresponded to the changes of partial pressure of CO2 (pCO2) in the seawater from 83% to 49% and pH from 4.8 to 6.1. [Copyright &y& Elsevier]

Abstract: We used laboratory experiments covering a wide range of carbon dioxide (CO2) induced seawater acidification to simulate ocean CO2 storage and assess the potential effects on heterotrophic microbial processes associated with labile dissolved organic matter (DOM). There was no noticeable effect of increased CO2 concentration on short-term decomposition of labile DOM or nutrient uptake. However, microbial activities producing “new” DOM were apparently enhanced under treatments with 2000 or 5000ppm CO2. Under these conditions, production of aggregates was inhibited in early stage. Both of acute and chronic effects should be included for assessment of biogeochemical cycle related to microbe process. [Copyright &y& Elsevier]

Abstract: The effects of UV irradiation on the respiration and survival of Escherichia coli in various concentrations of aqueous NaCl were investigated in the presence of a photocatalyst. In this study, we anticipated that the photocatalysis of residual chlorine generated in a solution containing Cl− would result in bacterial elimination. Our results indicated a gradual reduction in the E. coli survival ratio in freshwater; however, no decrease in total abundance was observed during 8 h of photocatalysis with UV irradiation. Conversely, the survival ratio of E. coli in the artificial seawater decreased drastically as a consequence of photocatalysis, with a concomitant decrease in total abundance. These results revealed that the chlorinated active species that formed on the photocatalyst surface influenced the observed inactivation. [Copyright &y& Elsevier]

Methods were developed to determine rates of particulate and dissolved protein synthesis via dark CO2 fixation by marine prokaryotic assemblages. The methods are based on incorporation of [14C]-bicarbonate and separation of proteins as TCA-insoluble materials. Results indicated that particulate protein constitutes a significant fraction (∼67%) of cellular organic matter produced via prokaryotic dark CO2 fixation. The microcentrifuge method allowed us to estimate the rate of total protein synthesis via CO2 fixation. Time-series data proved useful for determining the optimum incubation period, and for estimating the rate of protein synthesis by regression analysis. The total prokaryotic dark CO2 fixation rate (10.3 ng C l-1 h-1) estimated by these methods was 2.7-times the rate of particulate CO2 fixation, which was comparable to the CO2 fixation rate estimated by methods used in previous studies. Thus, total prokaryotic dark CO2 fixation appears to be more important in the marine carbon cycle than previously thought. [ABSTRACT FROM AUTHOR]

We investigated the effects of seawater acidification induced by ocean CO2 sequestration on bathypelagic prokaryotes. We simulated acidification conditions by bubbling high-CO2 air or adding chemical buffer solutions to seawater samples in order to examine changes in total cell counts, heterotrophic production rate, direct viable cell count, and relative abundance of Bacteria and Archaea. Considerable suppression of prokaryotic activities was observed at pH 7.0 or lower, especially in samples enriched with organic matter. The relative abundance of Archaea increased with increasing CO2 concentration. We found that seawater acidification can potentially alter heterotrophic activities and community structure of bathypelagic prokaryotes. [ABSTRACT FROM AUTHOR]