Evolution des hydrocarbures dans des sédiments côtiers méditerranéens prélevés à proximité d'un emissaire d'une raffinerie de pétrole

Coastal Mediterranean sediments highly polluted by refinery effluents have been studied for their hydrocarbon content and bacterial activity. The study has taken into account both the distance from the refinery and depth of sampling. Very high hydrocarbon concentrations have been found (1–250 g/kg dry sediment). Micro-organisms in the sediments have a high bacterial activity and a good correlation exists between hydrocarbon concentrations and bacteria able to use these substrates as a carbon and energy source.     

Changes in structural and functional diversity of nematode communities during a spring phytoplankton bloom in the southern North Sea

The response of nematode communities to the sedimentation of a spring phytoplankton bloom in a sandy, well-oxygenated sediment at a single station (station 330) in the Southern North Sea was investigated monthly from early March to July 1999. Both structural (nematode density, diversity, vertical distribution and community composition) and functional (feeding type distributions, number of species within feeding groups) characteristics showed considerable changes shortly after the arrival of fresh organic material at the sediment surface. The general increase in numerical densities and diversity was related to changes within the groups of selective deposit-feeding and epistrate-feeding nematodes. It is hypothesised that sedimentation and subsequent remineralisation of fresh organic matter during the spring phytoplankton bloom result in an increase of suitable food items (both living and dead). This, combined with the availability of oxygen, creates conditions in which many nematode species can co-exist.     

Idealised flow models to predict alluvial sandstone body distribution in the Middle Jurassic Yorkshire Basin

Prediction of the subsurface position of alluvial channel sandstones is of great importance in the search for potential hydrocarbon reservoirs. For maximum production at minimum expense, wells need to be sited where there is abundant sandstone and, for enhanced oil recovery, detailed knowledge of sandstone-body geometry and connectivity is desirable. Attempts to predict the position of sandstone-bodies in the subsurface have included theoretical computer simulation and detailed empirical modelling of alluvial architecture (three-dimensional rock type distributions). Up to now, no reliable predictive method has been developed and any improvement is of significance.The method presented here combines the theoretical approach to tectonic control of alluvial architecture with the available geological data to predict subsurface concentrations and orientations of alluvial sandstone bodies.     

Stoneley waves,Lopez Island noise,and deep sea noise from 1 to 5 Hz

The Lopez Island OBS Intercomparison Experiment provided a data set of sufficient spatial density to allow study of the propagation of shot-generated Stoneley waves as well as ambient background noise. The Stoneley waves were observed propagating at velocities of 20 to 50 m s^-1, Phase velocities were determined by fitting peaks in the frequency wave number spectrum. Group velocities were calculated by narrowly filtering the data and determining the arrival time of the peak in the frequency packet. Particle displacement plots illustrate the surface wave character of these waves. The analysis of the ambient background noise failed to produce a clearly defined dispersion curve yet it did allow bounds to be placed on the phase velocities (20 to 50 m s^-1). The data were modeled using eleven layers overlying a half-space. The results indicated that the top 7 m of the sediment column at Lopez Island is best approximated by two zones. In the upper zone there is a fairly rapid change of shear velocity with depth. This zone overlies a region in which the shear velocity gradient is much lower. Deep ocean background noise recorded by University of Washington ocean bottom seismometers was also examined. Although insufficient data precluded any velocity analysis, definite similarities exist between these data and noise data observed at Lopez Island.Hawaii Institute of Geophysics Contribution No. 1174.     

Absolute Calibration of Jason-1 and TOPEX/Poseidon Altimeters in Corsica

The double geodetic Corsica site, which includes Ajaccio-Aspretto and Cape Senetosa (40 km south Ajaccio) in the western Mediterranean area, has been chosen to permit the absolute calibration of radar altimeters. It has been developed since 1998 at Cape Senetosa and, in addition to the use of classical tide gauges, a GPS buoy is deployed every 10 days under the satellites ground track (10 km off shore) since 2000. The 2002 absolute calibration campaign made from January to September in Corsica revealed the necessity of deploying different geodetic techniques on a dedicated site to reach an accuracy level of a few mm: in particular, the French Transportable Laser Ranging System (FTLRS) for accurate orbit determination, and various geodetic equipment as well as a local marine geoid, for monitoring the local sea level and mean sea level. TOPEX/Poseidon altimeter calibration has been performed from cycle 208 to 365 using M-GDR products, whereas Jason-1 altimeter calibration used cycles from 1 to 45 using I-GDR products. For Jason-1, improved estimates of sea-state bias and columnar atmospheric wet path delay as well as the most precise orbits available have been used. The goal of this article is to give synthetic results of the analysis of the different error sources for the tandem phase and for the whole studied period, as geophysical corrections, orbits and reference frame, sea level, and finally altimeter biases. Results are at the millimeter level when considering one year of continuous monitoring; they show a great consistency between both satellites with biases of 6 ± 3 mm (ALT-B) and 120 ± 7 mm, respectively, for TOPEX/Poseidon and Jason-1.     

Effect of rainfall as a component of climate change on estuarine fish production in Queensland, Australia

The speculation that climate change may impact on sustainable fish production suggests a need to understand how these effects influence fish catch on a broad scale. With a gross annual value of A$ 2.2 billion, the fishing industry is a significant primary industry in Australia. Many commercially important fish species use estuarine habitats such as mangroves, tidal flats and seagrass beds as nurseries or breeding grounds and have lifecycles correlated to rainfall and temperature patterns. Correlation of catches of mullet (e.g. Mugil cephalus) and barramundi (Lates calcarifer) with rainfall suggests that fisheries may be sensitive to effects of climate change. This work reviews key commercial fish and crustacean species and their link to estuaries and climate parameters. A conceptual model demonstrates ecological and biophysical links of estuarine habitats that influences capture fisheries production. The difficulty involved in explaining the effect of climate change on fisheries arising from the lack of ecological knowledge may be overcome by relating climate parameters with long-term fish catch data. Catch per unit effort (CPUE), rainfall, the Southern Oscillation Index (SOI) and catch time series for specific combinations of climate seasons and regions have been explored and surplus production models applied to Queensland's commercial fish catch data with the program CLIMPROD. Results indicate that up to 30% of Queensland's total fish catch and up to 80% of the barramundi catch variation for specific regions can be explained by rainfall often with a lagged response to rainfall events. Our approach allows an evaluation of the economic consequences of climate parameters on estuarine fisheries, thus highlighting the need to develop forecast models and manage estuaries for future climate change impact by adjusting the quota for climate change sensitive species. Different modelling approaches are discussed with respect to their forecast ability.     

Knowledge production, organisation and agglomeration economies

The increasing attention for the economic value of the scientific work produced in universities has resulted in a multitude of concepts concerning the production and transfer of knowledge and possible linkages with the business community. Many universities are engaged in activities aimed at improving the economic development of their respective regions. They often participate in Science Parks, Techno Parcs, and Technopoles. They attempt to stimulate spin-offs and to promote the further use of the knowledge produced in their departments. The regional economic impact varies with the kind of knowledge involved. Only certain parts can be put to commercial use, more in particular the technological products of the knowledge output. Property rights of knowledge have to be defended, which makes it less easy to imitate or use the knowledge in other regions. The current trend to sell knowledge makes it necessary to build a strong organisational structure, especially in the first stages of the production of knowledge that is commercially applicable. Such an organisation requires huge funds and the establishment of strong teams of experts, to prevent valuable knowledge from premature dissipation. These teams and departments have better prospects in larger urban areas with a strongly differentiated economy, with agglomeration economies and lower transaction costs. In these regions it will be easier to have spin-offs (new firms) and to retain a linkage with entrepreneurs-alumni from the universities. An efficient organisation is an important precondition for successful universities and regions.