Studies on Migratory Movements of the Prawn Penaeus kerathurus (Forskal, 1775) at Amvrakikos Gulf, Western Greece

Abstract. The prawn Penaeus kerathurus completes its life cycle in Amvrakikos Gulf. The reasons for not entering the open sea depend on the status of biotic and abiotic factors of the gulf. The migratory movements of the species in the gulf are described by a simple square model, in each corner of which, the wintering, spawning, nursery, and recruitment area exist. The wintering area is located below the 25m isobath and wintering period lasts from late December to late March. Spermatophores on females are observed throughout the year but the highest percentages between April and August. The spawning season begins late in spring and continues through the summer. The spawning area is located below the 10m isobath, mainly around 25m. The nursery area of Penaeus kerathurus is in shallow waters near river estuaries, and the temporal limits were determined to be between mid-summer and mid-autumn. Finally, the recruitment area is located near the nursery area, with recruitment taking place in autumn, while the major stock renewal is restricted to winter.     

Selenium speciation and partitioning within Burkholderia cepacia biofilms formed on α-Al2O3 surfaces

The distribution and speciation of Se within aerobic Burkholderia cepacia biofilms formed on α-Al₂O₃ (1-102) surfaces have been examined using grazing-angle X-ray spectroscopic techniques. We present quantitative information on the partitioning of 10⁻⁶ M to 10⁻³ M selenate and selenite between the biofilms and underlying alumina surfaces derived from long-period X-ray standing wave (XSW) data. Changes in the Se partitioning behavior over time are correlated with microbially induced reduction of Se(VI) and Se(IV) to Se(0), as observed from X-ray absorption near edge structure (XANES) spectroscopy.Selenite preferentially binds to the alumina surfaces, particularly at low [Se], and is increasingly partitioned into the biofilms at higher [Se]. When B. cepacia is metabolically active, B. cepacia rapidly reduces a fraction of the SeO₃²⁻ to red elemental Se(0). In contrast, selenate is preferentially partitioned into the B. cepacia biofilms at all [Se] tested due to a lower affinity for binding to the alumina surface. Rapid reduction of SeO₄²⁻ by B. cepacia to Se(IV) and Se(0) subsequently results in a vertical segregation of Se species at the B. cepacia/α-Al₂O₃ interface. Elemental Se(0) accumulates within the biofilm with Se(VI), whereas Se(IV) intermediates preferentially sorb to the alumina surface.B. cepacia/α-Al₂O₃ samples incubated with SeO₄²⁻ and SeO₃²⁻ when the bacteria were metabolically active result in a significant reduction in the mobility of Se vs. X-ray treated biofilms. Remobilization experiments show that a large fraction of the insoluble Se(0) produced within the biofilm is retained during exchange with Se-free solutions. In addition, Se(IV) intermediates generated during Se(VI) reduction are preferentially bound to the alumina surface and do not fully desorb. In contrast, Se(VI) is rapidly and extensively remobilized.     

MétéEAU Nappes: a real-time water-resource-management tool and its application to a sandy aquifer in a high-demand irrigation context

The MétéEAU Nappes water-resource-management tool is presented. It is usable on the aquifer or part-of-aquifer scale for real-time observation of the state of the groundwater resource, and it is already operating in France. This online decision support tool is also able to predict the state of the resource in the short- and mid-terms. The paper explains the use of the tool in a case study in the Authion Valley, in the north-west of France, chosen for its context of tension surrounding the groundwater resource resulting from high volumes of abstraction for irrigation. The results of the simulation highlight the advantages of MétéEAU Nappes as a tool for prediction and simulation of the state of the groundwater resource. The results also show the advantages of this type of tool for water resource management, such as supplying local actors with reliable and real-time observations of the aquifer and providing forecasts to anticipate possible water shortage.

     

Ancient subsurface structure beneath crater Clavius:constraint by recent high-precision gravity and topography data

With the increasing precision of the GRAIL gravity field models and topography from LOLA, it is possible to investigate the substructure beneath crater Clavius. An admittance between gravity and topography data is commonly used to estimate selenophysical parameters, including load ratio, crustal thickness and density, and elastic thickness. Not only a surface load, but also a subsurface load is considered in estimation. The algorithm of particle swarm optimization(PSO) with a swarm size of 400 is employed as well.Results indicate that the observed admittance is best-fitted by the modeled admittance based on a spherical shell model, which was proved to be unsatisfactory in the previous study. The best-fitted load ratio f is around-0.194. Such a small load ratio conforms to the direct proportion between the nearly uncompensated topography and its corresponding negative gravity anomaly. It also indicates that a surface load dominates all the loads. Constrained within 2σSTD, a small crustal thickness(～30 km) and a crustal density of ～2587 kg m-3are found, quite close to the results from previous GRAIL research. Considering the well constrained crustal thickness and density, the best-fitted elastic thickness(～7 km) is rational. This result is slightly smaller than the previous study(～12 km). Such difference can be attributed to the difference in crustal density used and the precision of gravity and topography data. Considering that the small difference between the modeled gravity anomaly and observations is quite small, a parameter inversed here could be an indicator of the subsurface structure beneath Clavius.     

Formation and disruption of aquifers in southwestern Chryse Planitia, Mars

We present geologic evidence suggesting that after the development of Mars' cryolithosphere, the formation of aquifers in southwestern Chryse Planitia and their subsequent disruption led to extensive regional resurfacing during the Late Hesperian, and perhaps even during the Amazonian. In our model, these aquifers formed preferentially along thrust faults associated with wrinkle ridges, as well as along fault systems peripheral to impact craters. The characteristics of degraded wrinkle ridges and impact craters in southwestern Chryse Planitia indicate a profound role of subsurface volatiles and especially liquid water in the upper crust (the upper one hundred to a few thousands of meters). Like lunar wrinkle ridges, the martian ones are presumed to mark the surface extensions of thrust faults, but in our study area the wrinkle ridges are heavily modified. Wrinkle ridges and nearby plains have locally undergone collapse, and in other areas they are associated with domical intrusions we interpret as mud volcanoes and mud diapirs. In at least one instance, a sinuous valley emanates from a modified wrinkle ridge, further indicating hydrological influences on these thrust-fault-controlled features. A key must be the formation of volatile-rich crust. Primary crustal formation and differentiation incorporated juvenile volatiles into the global crust, but the crustal record here was then strongly modified by the giant Chryse impact. The decipherable rock record here begins with the Chryse impact and continues with the resulting basin's erosion and infilling, which includes outflow channel activity. We propose that in Simud Vallis surface flow dissection into the base of the cryolithosphere-produced zones where water infiltrated and migrated along SW-dipping strata deformed by the Chryse impact, thereby forming an extensive aquifer in southwestern Chryse Planitia. In this region, compressive stresses produced by the rise of Tharsis led to the formation of wrinkle ridges. Zones of high fracture density within the highly strained planes of the thrust faults underlying the wrinkle ridges formed regions of high permeability; thus, groundwater likely flowed and gathered along these tectonic structures to form zones of elevated permeability. Volatile depletion and migration within the upper crustal materials, predominantly along fault systems, led to structurally controlled episodic resurfacing in southwestern Chryse Planitia. The erosional modification of impact craters in this region is linked to these processes. This erosion is scale independent over a range of crater diameters from a few hundred meters to tens of kilometers. According to our model, pressurized water and sediment intruded and locally extruded and caused crustal subsidence and other degradational activity across this region. The modification of craters across this wide range of sizes, according to our model, implies that there was intensive mobilization of liquid water in the upper crust ranging from about one hundred to several thousand meters deep.     

Early Eocene magnetostratigraphy and tectonic evolution of the Xining Basin,NE Tibet

The Cenozoic strata of the Xining Basin, NE Tibet, have provided crucial records for understanding the tectonic and palaeo-environmental evolution of the region. Yet, the age of the lower part of the sedimentary stratigraphy and, consequently, the early tectonic evolution of the basin remain debated. Here, we present the litho- and magnetostratigraphy of various early Eocene sections throughout the Xining Basin independently constrained by the U–Pb radiometric age of a carbonate bed. Our study extends the dated stratigraphy down to 53.0 Ma (C24n.1r) and reveals highly variable accumulation rates during the early Eocene ranging from 0.5 to 8 cm/ka. This is in stark contrast to the low but stable accumulation rates (2–3 cm/ka) observed throughout the overlying Palaeogene and Neogene strata. Such a pattern of basin infill is not characteristic of flexural subsidence as previously proposed, but rather supports an extensional origin of the Xining Basin with multiple depocentres, which subsequently coalesced into a more stable and slowly subsiding basin. Whether this extension was related to the far-field effects of the subducting Pacific Plate or the India–Asia collision remains to be confirmed by future studies.     

Interaction Between Macrophytobenthic Groups on the Sublittoral Belt of a Greek Island

Abstract. The interrelationships between the main phytobenthic groups of Chlorophyceae, Phaeophyceae, and Rhodophyceae around Milos Island, Central Aegean Sea, were studied using standard ecological and mathematical methods. The analysis was based on seasonal sampling of 114 different macrophytobenthic species.
The employed ecological indices revealed that the sampling areas located on the north, south, and east side of Milos Island show similar annual fluctuations in abundance and species diversity. The resemblance was particularly high between all stations in October-February, between south and east stations during May, and between north and east stations during July.
Additionally, an annual cycle of group interaction with regard to species diversity and abundance exists between the Chlorophyceae, Rhodophyceae, and Phaeophyceae. The Rhodophyceae are the most abundant and dominant group throughout the year, showing percentages in the samples higher than 70% in all sampling areas.