A new look at the alkalinity of the Sea of Japan

The most important feature of the distribution of the alkalinity and calcium in the Sea of Japan—the increase in the potential alkalinity with depth under the conditions when the waters are supersaturated in relation to calcium carbonate—is considered. It is demonstrated that this fact cannot be accounted for by the reaction of the formation-dissolution of calcium carbonate. A new concept explaining the alkalinity distribution in the sea is proposed. According to it, the biological pump is the basic process responsible for the alkalinity transport from the euphotic layer into the interior of the sea. Photosynthesis is the driving force for this process. The role of the active element transporting the alkalinity is not calcium carbonate, as has been claimed elsewhere, but extracellular polysaccharides (EPSs) produced by phytoplankton. EPSs bind to calcium and other cations to form transparent exopolymer particles (TEPs). The proposed conception makes it possible to explain the following: (a) the vertical flux of calcium carbonate that is independent of the super-saturation—undersaturation state of the ambient water regarding calcium carbonate; (b) the existence of the calcium carbonate flux regardless of the nature of the plankton skeletons; (c) the nonstoichiometric ratio between the alkalinity and calcium fluxes.     

Long‐term nitrogen and phosphorus fertilization effects on N2 fixation rates and nifH gene community patterns in mangrove sediments

The bioavailability of nutrients is important in controlling ecological processes and nitrogen cycling in oligotrophic mangrove forests, yet the variation of diazotrophic community structure and activity with nutrient availability in sediments remains largely unexplored. To investigate for the first time how nutrients in sediments affect spatial and temporal patterns of diazotrophic community structure and activity, the sedimentary environment of Twin Cays, Belize, was examined with respect to the effects of long‐term fertilization [treatments: control (Ctrl), nitrogen (N), and phosphorus (P)] on N₂ fixation rates and nifH gene community structure. We found that N₂ fixation rates were significantly higher at the P‐treatment, intermediate at the Ctrl‐treatment and lower in the N‐treatment (P: 4.2 ± 0.5, Crtl: 0.8 ± 0.1, N: 0.4 ± 0.1 nmol·N·g^?1·h^?1; P < 0.001) with spatial (Ctrl‐ and P‐treatments) and temporal (only P‐treatment) variability positively correlated with live root abundance (r² = 0.473, P < 0.001) and concentration (r² = 0.458, P < 0.0001). The community structure of diazotrophs showed larger spatial and temporal variability in the fertilized treatments than in the Ctrl‐treatment, with the relative abundance of OTUs (nifH operational taxonomic units) at the fertilized treatments inversely related to live root abundance. Overall, long‐term fertilization (with either N or P) affects not only nutrient levels in mangrove sediments directly, but also spatial and temporal patterns of both community structure and activity and likely plant‐microbe interactions as well. Our findings suggest that the maintenance of natural nutrient conditions in mangrove sediments is important to ensure the stability of microbial functional groups like diazotrophs.     

Change in biochemical and morphological characteristics of Lonicera caerulea in tectonically active zone of the Dzhazator River Valley (Altai Mountains)

Local geophysical and geochemical anomalies affect the polymorphism of taste variations, berry shape, and content of some biologically active substances in Lonicera caerulea leaves in the tectonically active Altai Mountains (Dzhazator River basin).     

Estimation of methane fluxes from bottom sediments of Lake Baikal

Methane bubble fluxes in gas flares from bottom sediments in Lake Baikal were estimated for the first time using hydroacoustic methods. Earlier work has demonstrated the occurrence of gas seeps both inside and outside of areas where bottom simulating reflectors were identified in seismic profiles. Fluxes ranged from 14 to 216 tons per year, with the flux for the entire area of the central and southern basins ranging from 1,400 to 2,800 tons per year. Comparison with other water bodies showed that fluxes from the most intensive Baikal flares were similar to those in the Norwegian and Okhotsk seas. Gas hydrates decompose at the lower boundary of the gas hydrate stability zone due to sedimentation. Calculation of the amount of methane produced due to sedimentation gave a total of between 2,600 and 14,000 tons per year for the central and southern basins of the lake. Based on rough estimation, the total flux from shallow- and deep-water gas seeps is similar to the amount of methane produced due to sedimentation. This suggests that gas hydrates possibly occupy much more than 10?% of the pore volume near the base of the gas hydrate stability zone, or that there are other reasons for gas hydrate dissociation and bubble flux from these bottom sediments.     

Authigenic iron oxide formation in the estuarine mixing zone of the Yangtze River

Estuaries are elementary geochemical fronts where river water and seawater mix. Within this mixing zone, iron and other non-conservative elements can undergo complex reactions to form new solid phases. In order to understand authigenic iron oxide formation in the Yangtze River Estuary, two onsite water-mixing sets of experiments were conducted, one by mixing variable amounts of unfiltered Yangtze River water with filtered East China Sea water of different salinity (set 1), the other by mixing variable amounts of filtered Yangtze River water with filtered East China Sea water of different salinity (set 2). In set 2, the minerals newly formed in the course of mixing were investigated by means of a scanning electron microscope fitted with an energy-dispersive X-ray analytical system. It was found that ferrihydrite and lepidocrocite were formed in these mixing experiments, coexisting in nearly equal amounts. These iron oxides appear as aggregated particles with a large grain-size range of several microns to more than 100 μm. The electrolytic properties of seawater played an important role in the formation of these authigenic iron oxides. Kaolinite and organic aggregates were also found in the experimentally mixed pre-filtered waters. Amounts of newly formed suspended matter (set 2) were one to three orders of magnitude lower than those of total suspended matter (TSM) (set 1). This implies that newly formed minerals represent only a very small proportion of TSM in the estuarine mixing zone of the Yangtze River.     

Development of means and methods of drifter technology applied to the problem of the Black Sea research

During the last ten years, autonomous drifting platforms for data collection (drifters) equipped with Argos satellite communication devices have become one of the main components for the observation system in the upper layer of the ocean and surface atmosphere. This article presents the results of the Black Sea drifter monitoring in 2002–2006 within a number of international programs and projects. During this period, about 70 drifters manufactured by NPF Marlin-Yug Ltd. (Sevastopol, Ukraine) were deployed in the western part of the Black Sea. The drifters were mainly standard barometric Lagrangian tracers and a part of them were principally new temperature profiling buoys. Unique long-term data were obtained about the circulation of the surface currents and the dynamics of the temperature stratification within the seasonal thermocline and the cold intermediate layer.     

Physical modeling of long-range infrasonic propagation in the atmosphere

The results of experiments on the physical modeling of long-range infrasonic propagation in the atmosphere are given. Such modeling is based on the possible coincidence between the forms of the vertical profiles of the effective sound speed stratification in the atmospheric boundary layer (between 0 and 600 m for the case under consideration) and in the atmosphere as a whole (from the land surface up to thermospheric heights (about 150 km)). The source of acoustic pulses was an oscillator of detonation type. Owing to the detonation of a gas mixture of air (or oxygen) and propane, this generator was capable of producing short, powerful (the maximum acoustic pressure was on the order of 30 to 60 Pa at a distance of 50 to 100 m from the oscillator), and sufficiently stable acoustic pulses with a spectral maximum at frequencies of 40 to 60 Hz and a pulsing period of 20 to 30 s. The sites of acoustic-signal recording were located at different distances (up to 6.5 km) from the source and in different azimuthal directions. The temperature and wind stratifications were monitored in real time during the experiments with an acoustic locator—a sodar—and a temperature profiler. The data on the physical modeling of long-range sound propagation in the atmosphere are analyzed to verify the physical and mathematical models of predicting acoustic fields in the inhomogeneous moving atmosphere on the basis of the parabolic equation and the method of normal waves. A satisfactory agreement between calculated and experimental data is obtained. One more task was to compare the theoretical relations between variations in the azimuths and angles of tilting of sound rays about the horizon and the parameters of anisotropic turbulence in the lower troposphere and stratosphere with the experimental data. A theoretical interpretation of the experimental results is proposed on the basis of the theory of anisotropic turbulence in the atmosphere. The theoretical and experimental results are compared, and a satisfactory agreement between these results is noted.     

The role of water mass dynamics in controlling bacterial abundance and production in the middle Adriatic Sea

Month-to-month fluctuations in the abundance of bacteria and heterotrophic nanoflagellates (HNF) and bacterial production, as well as various chemical (nutrients, oxygen) and physical (salinity, temperature) parameters were analysed at a station located in the open middle Adriatic Sea during one decade (1997-2006). Being influenced by both coastal waters and open Adriatic circulation in the surface layer, and by the deep Adriatic water masses in the deep layers (100 m), this station is quite suitable for detecting the environmental changes occurring in the open Adriatic Sea with respect to the circulation of its water masses and their long-term changes and anomalies. Multivariate methods were used to identify seasonal and inter-annual changes of the investigated parameters, associating observed changes to the changes in Adriatic water masses and circulation regimes. The analyses showed that bacterial abundance and production were controlled by different water mass dynamics during 1997-2001 compared to 2002-2006 period, particularly noticeable in different seasonal patterns of biological parameters. The interplay between North Adriatic Dense Water (NAdDW) and Levantine Intermediate Water (LIW) resulted in a change in the available nutrients (NAdDW is poor in orthophosphates), and as a consequence different bacterial abundance and production. A few periods were examined in detail, such as 2004, when LIW inflow was particularly strong and was accompanied by an increase of bacterial and HNF abundances, as well as of bacterial production.