Variations of antioxidant efficiency and presence of endosymbiotic diatoms in the Antarctic porifera Haliclona dancoi

The role of endosymbiotic diatoms as pro-oxidant stressors in porifera has been investigated in the Antarctic sponge Haliclona dancoi in which the presence of diatoms is influenced by marked seasonal variations during the austral summer. Both chlorophaeopigments and frustules were absent in sponge tissues sampled in early November at the beginning of the summer and increased from the mid of December with slightly shifted temporal trends. The efficiency of antioxidant defenses in the sponge showed a marked response to symbionts with clearly enhanced values corresponding to the peak of diatoms.     

Twelve years of tracking 52-Hz whale calls from a unique source in the North Pacific

A unique whale call with 50–52 Hz emphasis from a single source has been tracked over 12 years in the central and eastern North Pacific. These calls, referred to as 52-Hz calls, were monitored and analyzed from acoustic data recorded by hydrophones of the US Navy Sound Surveillance System (SOSUS) and other arrays. The calls were noticed first in 1989, and have been detected and tracked since 1992. No other calls with similar characteristics have been identified in the acoustic data from any hydrophone system in the North Pacific basin. Only one series of these 52-Hz calls has been recorded at a time, with no call overlap, suggesting that a single whale produced the calls. The calls were recorded from August to February with most in December and January. The species producing these calls is unknown. The tracks of the 52-Hz whale were different each year, and varied in length from 708 to 11,062 km with travel speeds ranging from 0.7 to 3.8 km/h. Tracks included (A) meandering over short ranges, (B) predominantly west-to-east movement, and (C) mostly north-to-south travel. These tracks consistently appeared to be unrelated to the presence or movement of other whale species (blue, fin and humpback) monitored year-round with the same hydrophones.     

An overview of Mediterranean Ridge collisional accretionary complex as deduced from multichannel seismic data

 The Mediterranean Ridge (eastern Mediterranean) is a large accretionary complex that results from the Africa–Europe–Aegean plates convergence. Multichannel seismic data, combined with previous results showed that the ridge comprises distinct major structural domains facing different forelands: (1) An outer domain is bounded to the south by the ridge toe. Underneath the Ionian and Levantine outer Ridge, Messinian evaporites act as a major decollement level. (2) An axial, or crestal, ridge domain with mud diapiric and mud volcano activity is bounded to the north by backthrust. (3) A less tectonized inner Ridge domain, possibly a series of former forearc basins, abuts the Hellenic Trench. The ridge displays strong along-strike variations. These variations can be interpreted as consequences of an ongoing collision against the Libyan continental promontory.     

Spatial and temporal variability of particulate matter in the benthic boundary layer at the N.W. European Continental Margin (Goban Spur)

Near bottom water samples and sediments were taken during five cruises to 6 stations forming a transect across the N.W. European Continental Margin at Goban Spur. Flow velocity spot measurements in the benthic boundary layer (BBL) always increased from the shelf to the upper slope (1470 m) from 5 to 9 cm s⁻¹ in spring/summer and from 15 to 37 cm s⁻¹ in autumn/winter. Decreasing values were detected at the lower slope (2000 m) and the lowest values of ca. 2 cm s⁻¹ at the continental rise at 4500 m water depth. Long term measurements with a benthic lander at 1470 m show that currents have a tidal component and reach maximum velocities up to 20 cm s⁻¹, sufficiently high periodically to resuspend and transport phytodetritus. During these long-term observations, currents were always weaker in spring/summer than in autumn/winter. Critical shear velocities of shelf/slope sediments increased with depth from 0.5 to 1.7 cm s⁻¹ and major resuspension events and Intermediate Nepheloid Layers (INLs) should occur around 1000 m. Chloroplastic Pigment Equivalents (CPE) ranged from 0.0 to 0.21 μg dm⁻³, Particulate Organic Carbon (POC) from 12 to 141 μg dm⁻³ and Total Particulate Matter (TPM) from 0.2 to 10.0 mg dm⁻³. Aggregates in the BBL occurred with a median diameter of 152 to 468 μm. Data on suspended particulate matter in the near-bottom waters showed that hydrodynamic sorting within the particulate organic fraction occurred. Phytodetritus was packaged in relatively large aggregates and contributed little to the total organic carbon pool in nearbottom waters (CPE/POC ca.0.2%). The main organic fraction has low settling velocities and high residence times within the benthic boundary layer. As POC was not concentrated in the near bed region the degree to which carbon is accessible to the benthic community depends on aggregate formation, subsequent settling and/or biodeposition of the POC. Close to the sea bed downslope transport may dominate. Under flow conditions high enough to resuspend fresh phythodetritus from sediments at the productive shelf edge, this could be transported to 1500 m (Goban Spur) or abyssal depth (Canyon site between Meriadzek and Goban Spur) within 21 days.     

Gonadal development in Japanese medaka (Oryzias latipes) exposed to 17 β-estradiol

The purpose of this research was to evaluate the Japanese medaka (Oryzias latipes) as an ecotoxicological model for the rapid evaluation of environmental estrogens. A novel short-term (48-h) exposure to 17 β-estradiol is proposed in development of a positive control for disruption of gonadal development. Recently hatched medaka fry (30 fry per dose group) with undifferentiated gonads were exposed to 4.0, 29.4, and 115.6 μg/liter of 17 β-estradiol (acetone carrier) for 48 h in a water bath at 25 °C. The fry were then grown-out in spring water for 2 weeks, killed, and processed for histological evaluation. High lethality was encountered during the grow-out period in the 115.6 μg/liter dose group. Fry in the spring water and acetone (carrier) control groups developed into females or males. Fry exposed to 17 β-estradiol developed primarily into females or had testis-ova.     

Formation and chemical evolution of magnesium chloride brines by evaporite dissolution processes—Implications for evaporite geochemistry

The evolution of magnesium chloride brines with high bromide contents via a multistage reaction and dissolution process has been studied in brine seeps of a German potash mine. The observed chemical trends and phase equilibria can be modeled and interpreted in terms of a NaCl solution (cap rock brine) infiltrating into a potash zone characterized by the metamorphic mineral assemblage kieserite + sylvite + halite + anhydrite. Establishment of a persistent, stable equilibrium assemblage and constant fluid composition in the invariant point IP1 of the six component (Na-K-Mg-Ca-Cl-SO₄-H₂O) system of oceanic salts is prevented by the perpetually renewed input of NaCl-brine and by the intermittent exposure of incompatible kieserite. Instead, the solutions develop towards the metastable invariant point IP1(gy), with the mineral assemblage carnallite + polyhalite + sylvite + halite + gypsum, where gypsum takes the place of anhydrite (stage I). The temporary exposure of kieserite and the ensuing formation of polyhalite effectively buffer the solutions along the metastable polyhalite phase boundary during stages II and III. Eventually, in stage IV, polyhalite becomes depleted and admixture of more NaCl brine leads to low sulfate solution compositions, which are now only constrained by carnallite + sylvite + halite, and the once hexary system degenerates to a quaternary one (Na-K-Mg-Cl-H₂O) in point E. Bromide in brines shows equilibrium partitioning with respect to the wall rock minerals. The pattern of evolving brine compositions may serve as a model for similar brine occurrences, which in some cases may have been misinterpreted as remains of fossil, highly concentrated and chemically modified seawater. Similar magnesium chloride brines of salt lakes (e.g., Dead Sea, Dabusun Lake) show subtle differences and are constrained by fewer mineral equilibria (more degrees of freedom), and their low sulfate contents are due to gypsum precipitation, driven by calcium chloride input from dolomitization reactions. Finally, the observed reaction sequence is generalized, and a model for the formation of magnesium sulfate depleted, chloride-type potash salts and bischofite deposits by leaching of sulfate-type evaporites is proposed.     

A perturbation theory for Love waves in anelastic media

Summary. We give a systematic formulation and a rigorous justification of a perturbation technique for the computation of the eigenvalues and eigenfunctions of Love waves (and toroidal oscillations by an appropriate change for variables) in an anelastic medium with a constitutive law modelling geophysical media of current interest such as the Kelvin—Voigt Solid, the Maxwell Solid, the Standard Linear Solid, and the Standard Linear Solid with a continuous spectrum of relaxation times. We develop expressions relating the eigenvalues of eigenfunctions for Love waves in a continuously varying vertically stratified anelastic half-space to the corresponding elastic eigenvalues and eigenfunctions. Analytically, our correspondence principle has the form of a regular perturbation expansion in terms of a parameter for both the eigenvalues and eigenfunctions. The identification of ɛ is motivated by the dissipativity principle of viscoelasticity theory. Moreover, we show that our correspondence principle applies respectively only in the high and low frequency range for the Maxwell and Kelvin—Voigt Solids. Outside of the applicable range of frequencies, our correspondence principle yields no useful information. For the family of Standard Linear Solids it is uniformly applicable for all non-zero frequencies.
We also derive an explicit formula to estimate the radius of convergence of our perturbation expansions. This estimate of the radius of convergence for each eigenvalue and eigenfunction is functionally defined by the constitutive model for the anelastic medium. The estimate is frequency dependent and depends on the separation distance between the eigenvalue and the remainder of the spectrum of the corresponding elastic problem.     

Retrieval of optical characteristics of the aerosol atmosphere and Earth’s surface by the joint processing of different satellite information

Methods and algorithms for the retrieval of optical characteristics of the aerosol atmosphere and underlying surface by data from a multispectral satellite sensor (MSSS) are described. A procedure for the joint processing of MSSS and multizonal imaging system (MZIS) data is proposed and described with the aim of retrieving the albedo of the Earth’s surface with a high spatial resolution. In this case the spectral optical characteristics of the aerosol atmosphere are retrieved by MSSS data in the visible range of 400–700 nm. According to these results, transmission functions of the atmosphere in MZIS spectral channels are calculated and an atmospheric correction of MZIS data is performed. The accuracy of determining the albedo of the underlying surface in spectral channels of MZIS with high-spatial-resolution is estimated.     

Impact of subgrid-scale vegetation heterogeneity on the simulation of carbon-cycle characteristics

The carbon cycle module of the global climate model developed at the Obukhov Institute of Atmospheric Physics, Russian Academy of Sciences (IAP RAS CM) has been extended by implementing the subgrid-scale heterogeneity (SH) of plant functional types (PFTs). It is found that subgrid-scale PFT heterogeneity enhances the photosynthesis intensity and increases vegetation and soil carbon stocks in grass-dominated regions. In forest-dominated regions, photosynthesis is suppressed and vegetation and soil carbon stocks are diminished. Regionally, accounting for subgrid-scale vegetation heterogeneity may lead to twofold changes in these variables. On the whole, accounting for subgrid-scale PFT heterogeneity enhances (suppresses) the carbon flux in regions where it is directed from terrestrial ecosystems to the atmosphere (from the atmosphere to terrestrial ecosystems).