Evaluating the effects of catch-and-release angling on Cape stumpnose Rhabdosargus holubi in a South African estuary

Fisheries managers are increasingly promoting catch-and-release (C&R) to manage recreationally angled fish stocks. Despite this, there is a scarcity of information on the effects of C&R on estuarine-dependent species. Cape stumpnose Rhabdosargus holubi dominates the recreational fisheries catch and provides an important source of food for subsistence fishers in some temperate South African estuaries. The health and survival of R. holubi exposed to a C&R event was investigated by examining their physiological stress response (blood glucose and lactate), reflex impairment (reflex action mortality predictors [RAMP]) and short-term (12-hour) survival. Fish were captured and exposed to one of three air-exposure treatments: 0 s, 30 s or 90 s. Stress and health were measured either immediately (immediate) or one hour after (delayed) the C&R event. There was no significant difference in blood glucose between air-exposure treatments, but there was a significant difference between the mean immediate and delayed glucose levels within each treatment (F_(2,143) = 81.8, p < 0.01). In contrast, blood lactate level was significantly higher in the 90-s treatment (p < 0.05). Immediate blood lactate levels were significantly lower than the delayed samples for each treatment (F = 4.29, p = 0.02; n = 169). Although all fish exhibited at least one reflex impairment, the RAMP score was significantly higher in the 90-s air-exposure treatment (H_(2,86) = 9.73, p = 0.007). Also, RAMP scores were significantly lower in the delayed samples (p < 0.01). Although short-term mortality was relatively low (2.3%) for this species, it was highest in the 90-s treatment (7%). These results suggest that physiological stress is higher when R. holubi are exposed to longer periods of air exposure and that the physiological stress of fish subject to a C&R event is best measured after a delay.     

Oxygen and Sulfides in Bottom Sediments of the Coastal Sevastopol Region of Crimea

Spatial variations in the distribution and fluxes of dissolved oxygen and sulfide in bottom sediments of Omega and Sevastopol bays have been studied. The results of analysis reveal that the distribution of dissolved oxygen and sulfide in pore water depends mostly on seasonal variations in the oxygen concentration in bottom water, grain size, the organic carbon content in bottom sediments, and, additionally for Sevastopol Bay, the iron content. The oxygen flux at the bottom of Sevastopol Bay is 20 times larger in winter–spring compared to that of Omega Bay. Anaerobic conditions in Sevastopol Bay sediments are observed much closer to the surface, with their subsequent development in bottom water.     

Simulating the Propagation of Infrasonic Waves and Estimating the Energy of the Chelyabinsk Meteoroid Explosion Observed on February 15, 2013

Results obtained from simulating the propagation of infrasonic waves from the Chelyabinsk meteoroid explosion observed on February 15, 2013, are given. The pseudodifferential parabolic equation (PDPE) method has been used for calculations. Data on infrasonic waves recorded at the IS31 station (Aktyubinsk, Kazakhstan), located 542.7 km from the likely location of the explosion, have been analyzed. Six infrasonic arrivals (isolated clearly defined pulse signals) were recorded. It is shown that the first “fast” arrival (F) corresponds to the propagation of infrasound in a surface acoustic waveguide. The rest of the arrivals (T1–T5) are thermospheric. The agreement between the results of calculations based on the PDPE method and experimental data is satisfactory. The energy E of the explosion has been estimated using two methods. One of these methods is based on the law of conservation of the acoustic pulse I, which is a product of the wave profile area S/2 of the signal under analysis and the distance to its source E _I [kt] = 1.38 × 10^–10 (I [kg/s])^1.482. The other method is based on the relation between the energy of explosion and the dominant period T of recorded signal E _T [kt] = 1.02 × (T [s]²/σ)^3/2, where σ is the dimensionless distance determining the degree of nonlinear effects during the propagation of sound along ray trajectories. According to the data, the explosion energy E _I,T ranges from 1.87 to 32 kt TNT.     

Baikal Electromagnetic Experiment

Izvestiya, Atmospheric and Oceanic Physics - The vertical component of the electric field Ez in the hydrosphere is not contaminated by the telluric component and therefore can effectively be used...     

Extreme Climatic Events in the Altai-Sayan Region as an Indicator of Powerful Volcanic Eruptions

Izvestiya, Atmospheric and Oceanic Physics - Analytic data on anomalies of the tree-ring structure of Siberian larch on the transect, passing through the Russian part of the Altai-Sayan Mountain...     

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.     

Diagnosis of trace metal contamination in sediments: the example of Ensenada and El Sauzal, two harbors in Baja California, Mexico

Total metal concentrations in sediments from within Ensenada and El Sauzal Harbors are generally higher than at the mouths. Grain-size analyses suggested that this enrichment could be due to the presence of fine-grained sediments in the inner part of the harbors rather than to anthropogenic perturbations. The (Me/Al)(sample) ratios for Pb, Co, Ni and Fe were significantly higher for Ensenada Harbor relative to El Sauzal Harbor, whereas the ratios for Cd, Mn, Zn and Cu were statistically equivalent for both harbors. Calculated enrichment factors [EF(Me)=(Me/Al)(sample)/(Me/Al)(shale)] indicated that the metals showing slight enrichment were those associated with anthropogenic contamination (Pb, Zn), or probably related to primary productivity in the water column (Cd, Co). The levels of most of the metals were not greatly enriched, a consideration that is of the utmost importance when contamination issues are at stake.