Energy sources for diagenesis: Evidence from the Black Sea

Complex investigations of recent and Drevnechernomorian (ancient Black Sea) sediments from the outer shelf, continental slope, and deep-water basin of the Russian Black Sea sector have been carried out using samples collected during cruise of the R/V Professor Shtokman organized by the Institute of Oceanology of the Russian Academy of Sciences (March 2009) and expedition of “YUZHMORGEO” (summer 2006). Rates of the main anaerobic processes during diagenesis (sulfate reduction, dark CO₂ fixation, methanogenesis, and methane oxidation) were studied for the first time in sediment cores of the studied area. Two peaks in the rate of microbial processes and two sources of these processes were identified: the upper peak near the water-sediment contact is related to the solar energy (OM substrate of the water column) and the lower peak at the base of the Drevnechernomorian sediments with high(>1000 μM) methane concentration related to the energy of anaerobic methane oxidation. The neogenic labile OM formed during this process is utilized by other groups of microorganisms. According to experimental data, the daily rate of anaerobic methane oxidation is many times higher than that of methanogenesis, which unambiguously indicates the migration nature of the main part of methane.     

Seasonal Variability of Vertical Fluxes of Dispersed Sedimentary Matter in the Black Sea

Doklady Earth Sciences - The main aim of this work is to obtain new data on the seasonal variability of the vertical flux of sedimentary matter, its composition, and its transformation during...     

Traces of paleoearthquakes in the Quaternary deposits of intermontane basins in central Gorny Altai

Study of the sections of Neopleistocene–Holocene deposits filling the basins in central Gorny Altai has revealed earthquake-induced soft-sediment deformation (seismites). They formed as a result of the brittle deformation of deposits and liquefaction of loose water-saturated sediments under vibration seismic impact. The paleoearthquakes resulting in such seismites had the minimum intensity I = 6 and magnitude M = 5–6. Hence, the study region underwent strong earthquakes in the Neopleistocene–Holocene.     

Geochemistry of hydrothermal solutions from 9°50′ N at the East Pacific Rise (EPR) within twelve years after the eruption of a submarine volcano

Hydrothermal solutions were examined in a circulation system that started to develop after the 1991 volcanic eruption in the axial EPR segment between 9°45′ N and 9°52′ N. Within the twelve years elapsed after the eruption, the diffusion outflow of hot fluid from fractures in basaltic lavas gave way to focused seeps of hot solutions through channels of hydrothermal sulfide edifices. The example of field Q demonstrates that the concentrations of H₂S decreased from 86 to 1 mM/kg from 1991 to 2003, and the Fe/H₂S ratio simultaneously increased by a factor of 1.7, a fact that can explain the disappearance of the microbial mats, which were widespread at the fields before 1991. The S isotopic composition of H₂S is independent of the H₂S concentration, a fact testifying to the rapid evolution of the hydrothermal system in the early years of its evolution. Carbon in CH₄ from the hot fluid sampled in 2003 is richer in the light ¹²C isotope than carbon in the fluid from the hydrothermal field at 21° N in EPR, which suggests that methane comes to field Q from more than one source. The composition of particulate matter in the hydrothermal solutions indicates that it was contributed by biological material. Experimental solutions with labeled substrates (t < 70°C) show evidence of the active processes of methane oxidation and sulfate reduction. Our results indicate that, during the 12 years of the evolution of the hydrothermal system, the composition of its solutions evolved and approached the compositions of solutions in mature hydrothermal systems in EPR.     

River pollution in ladoga basin: Estimation based on diatom index

A modification of water stream pollution index was developed based on the use of periphyton diatomic algae, taking into account the regional features of the Ladoga basin. Original values of indicator valences and weights are given for 60 mass taxa of diatoms. River water quality was found to deteriorate from the north to the south because of the higher economic development of the southern part of Ladoga basin. The zonal changes in water quality in large rivers is much less pronounced than in medium and small rivers, which have closer relationships with the local situation on the watershed. Studying the correlation of the modified index with total phosphorus concentration showed it to be more efficient in estimating the anthropogenic pollution of streams in Ladoga basin as compared with trophic datomic indices developed in Europe.     

Structure and Production Potential of Summer Phytoplankton of Lake Baikal in the Present Period

Water Resources - A study of the structure and production parameters of phytoplankton (biomass, photosynthesis rate, chlorophyll a content, and assimilation numbers) in the coastal and pelagic...