The significance of transparent exopolymeric particles in the vertical distribution of bacteria and heterotrophic nanoflagellates in Lake Pavin

The abundance, size distribution, and bacterial colonization of Transparent Exopolymeric Particles (TEP) were examined in two consecutive years during the spring diatom development throughout the water column of the deep meromictic Lake Pavin, France. TEP concentrations ranged from 1.9 to 13.4 × 10⁵ particles l⁻¹ and their distribution and size spectra indicated that these particles are the main factor in governing the transport of diatoms to the deep hypolimnion of the lake. The majority of TEP was colonized by bacteria that constituted 0.4–8.9% of total DAPI-stained bacteria. The intensity of bacterial colonization was strongly related to temperature and decreased with particle size. A more important colonization of small particles in the hypolimnion during thermal stratification suggested that bacterial colonisation also increased with the age of the particle. The abundance of heterotrophic nanoflagellates (HNF) was more significantly related to the density of particles than to the density of total bacteria and the intensity of bacterial colonization of TEP. Our results therefore suggest that TEP are a more important factor for HNF development than attached and free bacteria. We conclude that TEP are involved not only in sedimentation processes but also in the dynamics of bacteria and protozoa in freshwater pelagic environments.     

The stratospheric quasi-biennial oscillation observed in the semidiurnal ground pressure data

Ground pressure observations made at Macao (22^○N, 113^○E) from 1953 to 1991 are analyzed and compared with the stratospheric quasi-biennial oscillation (QBO) data obtained during the same interval. The periods of the two phenomena and their time evolution are found to be close to each other. Furthermore, the time series of the stratospheric winds and the S2(p) QBO signature are highly correlated, thus confirming earlier analysis. On this basis, pressure measurements obtained at Batavia (now Djakarta: 6^○S, 107^○E) from 1870 to 1944 are used to trace back the QBO phenomenon before the advent of systematic stratospheric balloon measurements. The inferred period, which varies between 25 and 32 months, suggests that the QBO has been present in the atmosphere at least since 1870.     

Spatiotemporal changes in cadmium contamination in the Seine estuary (France)

Cadmium (Cd) is among the major contaminants in the Seine estuary. In the biota, the RNO (Réseau National d’Observation, the French Mussel-Watch) has shown that Cd concentrations in mussels living at the mouth of the estuary are related to changes in inputs to this area of phosphogypsum, a calcium sulphate that is a by-product of the phosphoric acid naturally enriched with Cd. In the water column, Cd concentrations at several key estuary sites show a very marked trend toward decreased contamination in the particles as well as in the dissolved phase. The behavior of Cd in the estuary has been studied between 1991 and 1998 in the framework of the scientific program Seine-Aval. This program has highlighted punctual Cd inputs in the estuarine water column. The partition of Cd between the dissolved and the particulate phase, previously described in various estuaries, is characterized by an intense phenomenon of solubilization in the mixing zone freshwater-seawater, but the colloidal Cd fraction remains low along the whole salinity gradient, about 5% to 10% of the apparent dissolved fraction. Although the decrease of inputs induced a fall of Cd concentrations in the water column, laboratory experiments show that the estuarine particles are far from being exhausted in Cd. Despite continuous efforts to reduce the urban and industrial inputs into the estuarine and coastal waters, the Seine estuary still remains very contaminated by Cd.     

Ophiolite emplacement by strike-slip tectonics between the Pontide Zone and the Sakarya Zone in northwestern Anatolia, Turkey

Northwestern Anatolia contains three main tectonic units: (a) the Pontide Zone in the north which consists mainly of the Gstanbul-Zonguldak Unit in the west and the BallLda<-Küre Unit in the east; (b) the Sakarya Zone (or Continent) in the south, which is juxtaposed against the Pontide Zone due to the closure of Paleo-Tethys prior to Late Jurassic time; and (c) the Armutlu-OvacLk Zone which appears to represent a tectonic mixture of both zones. These three major tectonic zones are presently bounded by the two branches of the North Anatolian Transform Fault. The two tectonic contacts follow older tectonic lineaments (the Western Pontide Fault) which formed during the development of the Armutlu-OvacLk Zone. Since the earliest Cretaceous, an overall extensional regime dominated the region. A transpressional tectonic regime of Coniacian/Santonian to Campanian age caused the welding of the Gstanbul-Zonguldak Unit to the Sakarya Zone by an oblique collision. In the Late Campanian, a transtensional tectonic regime developed, forming a new basin within the amalgamated tectonic mosaic. The different tectonic regimes in the region were caused by activity of the Western Pontide Fault. Most of the ophiolites within the Armutlu-OvacLk Zone belong to the Paleo-Tethyan and/or pre-Ordovician ophiolitic core of the Gstanbul-Zonguldak Unit. The Late Cretaceous ophiolites in the eastern parts of the Armutlu-OvacLk Zone were transported from Neo-Tethyan ophiolites farther east by left-lateral strike-slip faults along the Western Pontide Fault. There is insufficient evidence to indicate the presence of an ocean (Intra-Pontide Ocean) between the Gstanbul-Zonguldak Unit and the Sakarya Zone during Late Cretaceous time.     

Assessment of sandstone deterioration at Ta Keo temple (Angkor): first results and future prospects

A first application of geomorphological methods to the assessment of sandstone deterioration at Angkor is presented. Damage diagnosis was carried out on the first eastern tier of the central pyramid of the 1,000 year-old Ta Keo temple. Methods combine field observations and measurements at 230 sampling points, high-resolution lasergrammetry and stereophotogrammetry on a 2-m² test zone, and SEM observations. The first results indicate that decay operates through a synergistic combination of weathering phenomena dominated by scaling and solution, and exhibits a high spatial variability. Percentages of deteriorated surfaces vary from 17.6 to 93.8%, and average stone recession values from 0.00 to 2.71 cm (minimum) and 0.34 to 5.49 cm (maximum). On the test-zone, stereophotogrammetry and 3D-mapping of the present and reconstructed initial states using lasergrammetry indicate that erosion scars up to 6 cm deep have formed since 1963. On the whole, the amount of deteriorated surfaces more than tripled between 1963 and 2008. The degree of implication of salts in stone decay remains unclear for most efflorescences are composed of calcite (CaCO3), with secondary importance of barite (BaSO4) and gypsum (CaSO₄·2H₂O). Future prospects aim to evaluate the impact on stone decay of the clearing out of the temple from the forest in the 1920s.