A new Fine Scale Sampler (FSS) was designed and used in the Loire River plume (Bay of Biscay, France) in order to study phytoplankton distribution in highly stratified water columns. The FSS consists of a linear array of 15 sampling bottles, set horizontally at 20cm intervals. Data acquired from the CTD and fluorescence probe of the FSS enable it to be precisely positioned at the depth of the highest density gradient or at the chlorophyll a maximum. The FSS made it possible to investigate fine scale vertical distribution of phytoplankton and relationships with water density, nutrient concentrations or light availability, for spring and summer conditions. Under spring conditions, the entire upper layer exhibited a dominant diatom population (Chaetoceros sociale, Thalassiosira rotula) above 15m with evident uptake in dissolved inorganic nutrients and the maximum concentration of dinoflagellates (mainly small forms of Gymnodinium spp. and Gyrodinium spp.) was located 16m deep, where light energy began to be a limiting factor for phytoplankton growth. During summer conditions, the maximum phytoplankton biomass (10μgl−1 of chlorophyll a) was only concentrated in the 2m thick pycnocline layer, located at a depth of 12m. The diatom C. sociale was dominant in the phytoplankton peak. Dinoflagellates (Dinophysis acuminata and Gymnodinium spp.) were also concentrated around the density gradient. Low inorganic nitrogen concentration (<0.2μmoll−1) was responsible for the limitation of phytoplankton production in the surface layer above the pycnocline, and the phytoplankton growth was irradiance-limited underneath the pycnocline.

Because of the occurrence of episodic blooms of toxic dinoflagellates, eutrophication of the Seine Bight is a subject of growing concern. In order to better understand the relationships between these processes and human activity in the Seine watershed, two models have been used in connection:•A model describing nutrient (N, P, Si) transfer processes at the scale of the whole Seine Basin (RIVERSTRAHLER [Billen, G., Garnier, J., Ficht, A., Cun, C., 2001. Modelling the response of water quality in the Seine River Estuary in response to human activity in the watershed over the last 50 years. Estuaries 24, 977–993]), allowing human activity (agricultural practices, waterscape management, urban wastewater management, etc.) to be related to fluxes delivered to the sea.•A model of 3D hydrodynamic and ecological model of the Seine Bight (SiAM-3D/ELISE [Cugier, P., 1999. Modélisation du devenir à moyen terme dans l'eau et le sédiment des éléments majeurs (N, P, Si, O) rejetés par la Seine en baie de Seine. Thèse de doctorat, Univ. de Caen, p. 241; Cugier, P., Le Hir, P., 2000. Modélisation 3D des matières en suspension en baie de Seine Orientale (Manche, France). C. R. Acad. Sci. Paris, Sciences de la Terre et des planétes 331, 287–294]), capable of reproducing the spatio-temporal variations of sediment transport, thermo-haline stratification and phytoplanktonic development in the plume of the Seine river.

A three-dimensional model, based on the coupling between a hydrodynamic part taking into account sediment dynamics (SiAM-3D) and an ecological part which accounts for the main biological compartments and processes, has been developed to study nutrient cycles (nitrogen, phosphorus, silica) and their contribution to phytoplankton stock regulation in the Bay of Seine (French coast of the English Channel). The role of each nutrient in phytoplankton production has been identified. Spring phosphorus and summer silicate limitation of diatom growth is observed and confirmed by the model. The simulations show a shift from spring nitrogen to spring phosphorus limitation of diatom growth between the 1970s and the 1990s which is related to an increase in Seine river nitrogen loading and a decrease in phosphorus. Several scenarios of nutrient input reductions were investigated and show a greater sensitivity of flagellates to these reductions. The use of an original numerical method to track the nutrient coming from different sources shows the non-negligible impact of offshore inputs in annual plankton production. In some cases, 50% of the annual diatom production could be related to open sea nitrogen loading. The annual production of flagellates supported by the open sea loading did not exceed 36%.

As part of the French National Programme for Coastal Oceanography, this paper focuses on improvement of biogeochemical modelling in the Bay of Seine (Eastern Channel), by introducing phosphorus in nutrient cycles. The Bay of Seine receives the Seine river, which exhibits very high nutrient concentrations, and this coastal zone constitutes a typical case of eutrophication in a river plume area. In terms of analyses, sequential extraction and analysis of sedimentary phosphorus were used in order to measure various forms of particulate phosphorus in suspended matter and sediment (calcium-bound phosphate, Fe/Al-bound phosphate, exchangeable phosphate and organic phosphorus). In the modelling approach, the Bay is divided into 42 boxes and a two-layer, vertical thermohaline model is linked with the horizontal circulation scheme to take vertical stratification into account. The previous biological sub-model, with only nitrogen and silicon as nutrients, was improved by taking account of (a) various forms of bioavailable phosphorus (dissolved phosphate, exchangeable phosphate and organic phosphorus) and (b) experimental parameters, which govern the adsorption/desorption of phosphate at the solid–water interface. The ecological model accurately reproduces dissolved nutrient behaviour in the river plume, and concentrations of diatoms, flagellates and zooplankton are consistent with observed values. Simulated exchangeable phosphate and organic phosphorus in suspended matter are in the range of measured concentrations, whereas these particulate variables are simulated with less accuracy in the sediment. After evaluating the respective roles of nitrogen, phosphorus and silicon as limiting factors for phytoplanktonic growth, the model was used to estimate consequences of reduced phosphorus or nitrogen input for phytoplanktonic production in the Bay of Seine.

As part of the Programme National d'Oceanographie Cotiere, the nutrient dynamics of the Bay of Seine were studied between 1992 and 1994 in order to complement work on ecological modelling. Firstly, the River Seine's nutrient fluxes were established: 80 000-130 000 t a(-1) of dissolved inorganic nitrogen, 6 400-8 400 t a(-1) of dissolved phosphorus and 20 000-77 000 t a(-1) of dissolved silicium. Estuarine processes were taken into account. Consequences of nutrient loading for the bay were then evaluated at the pelagic level (nutrient and chlorophyll enrichments) and the benthic level (distribution of various phosphorus fractions in superficial sediments). The large continental inputs always induce concentration gradients in the water from the mouth of the river to the northwest of the bay. The northward spreading of fine particulate matter controls the distribution of adsorbed phosphate and iron-aluminium bound phosphate in sediments. In contrast, calcium bound phosphate, the main fraction in sediments, is not affected by river inputs. Organic phosphorus in sediments is related to phytoplankton blooms, with increasing concentrations during productive periods; afterwards the fast recycling prevents sedimentary accumulation. The nutrient depletions observed beyond the turbid plume during spring 1992 enabled the calculation of nutrient uptake rates, and the comparison of these rates with phytoplankton biomass (chlorophyll a + phaeopigments). Ratios of nutrient consumption to pigment concentration were estimated at 1 mu mol mu g(-1) for nitrogen, 0.05 for phosphorus and 0.5 for silicate. These values, as N/P and Si/N uptake ratios (respectively 17.5 and 0.4), were similar to usual values. (C) Elsevier, Paris.

Along with the emergence of high-speed communication technologies and protocols, tools for multimedia applications are growing in terms of their variety and their performances, making multimedia data flows candidates to the integration in almost every computer system. We particularly focus on the case of the factory plant where audio and video equipments could soon take part in the control/monitoring of manufacturing processes. Our paper presents a novel architecture for real time distributed systems using a 155.52 Mbit/s ATM network. The system is based on an intelligent network interface board, which integrates a processor and a field programmable gate array component to implement flexible high level real time data services in an off-host implementation approach. Moreover, the embedded ATM switch allows to build a large variety of topologies and provides high speed communication links, in particular for audio and video streams, inside the workstation. We also propose an MMS-like multimedia application service element for the integrated service computer manufacturing system and present some target applications.

As part of a French National Program aiming at better understanding and modelling the coastal eutrophication process, the Bay of Seine (Eastern Channel) has been chosen as a typical case of phytoplanktonic eutrophication in a river plume.Flow rates and nutrient concentrations in the river Seine show a continuous increase of N loadings during the last decade, whereas Si loadings are stationary and P loadings decrease, due to a reduction of industrial discharges. Seasonal cruises made in 1978 and 1992 showed the nutrient enrichment of the eastern part of the Bay and the high chlorophyll content of the plume area, especially in the surface layer. In order to quantify the respective roles of horizontal advection, vertical stratification, meteorologically-induced versus man-induced variations of nutrient loadings in the global eutrophication process, the mathematical modelling approach was applied. Based on a one nautical mile mesh size map of computed lagrangian tidal residual currents, a box-model of the whole Bay of Seine has been built thanks to IFREMER's ''ELISE'' software. Using 1978 data, a simple model of N and Si biogeochemical cycles first revealed the main importance of vertical haline stratification in the phytoplanktonic proliferation process. Then, simulations combining rainy (1988) or dry (1990) discharge regimes with increasing nitrogen mean levels showed that the interannual fluctuation of the global marine phytoplanktonic production in the bay is mainly conditioned, through run-off, by the interannual meteorologic variations, which blur the relatively weaker effect due to anthropogenic gradual increase of nitrogen loadings.

Today, communication networks are growing in terms of size and speed, delivering hundreds of megabits to tens of gigabits per second. This large amount of bandwidth leads to the definition of new kinds of distributed applications introducing multimedia. Nevertheless, current computer architectures are not well suited to process these delay guaranteed and cumbersome flows. This paper particularly focuses on the factory plant case where multimedia equipments could soon be integrated in the control of manufacturing processes. First, a novel real time distributed architecture based on a 155 Mbit/s ATM network is introduced. The main features of the communication board are an embedded ATM switch, and a processor coupled with a programmable gate array in order to provide efficient high level communication protocols. Then, a MMS-like multimedia application service element for integrated manufacturing services is introduced. It takes advantage of the particular architecture of the network interface board

Computing and networking technologies allow the integration of continuous media data flows to almost every computer system. We particularly focus on the case of the factory and process control plants where audio, animation and video devices will soon take part in the control and the monitoring of manufacturing processes. We propose a MMS-like multimedia application service element (MASE) for the configuration and the management of multimedia devices and continuous media data streams on manufacturing and process control plants. We also propose a novel architecture for real-time distributed systems using a 155.52 Mbit/s ATM network. The system is based on an intelligent communication board integrating a processor and a field programmable gate array component on which MASE and other flexible high level communication functions are implemented. The embedded ATM switch provides high speed communication links inside the workstation. The main advantages of our architecture include: the reduction of the multimedia load imposed on the host processor, the provision of an efficient real-time data service to applications, and the support of the TCP/IP protocol.

The Bay of Seine receives the French river with the highest nutrient concentrations, especially phosphorus. Dissolved (phosphate) and particulate phosphorus fluxes have been determined from fortnightly serial data collected by the Port Autonome de Rouen. These determinants exhibit behaviour opposite to that of the river flow: phosphate concentration decreases hyperbolically and particulate phosphorus increases linearily. An approach based on the rate of domestic effluent treatment agrees well (20%) with the measured phosphate flux. The determination of the main particulate phosphorus forms (adsorbed, apatite, non-apatite inorganic, organic) was undertaken over the whole estuarine salinity range. The speciation of particulate phosphorus exhibits a great homogeneity, irrespective of the salinity and the time of the year. From this study, it may be concluded that some 50% of the particulate phosphorus is potentially bioavailable. Heavy loads of particles expelled from the estuary during spring floods may therefore significantly contribute to the enrichment of the bay at the time when phytoplankton is actively growing.

The aim of this paper is to present some results of bacterial studies which were developed by IFREMER in coastal discharge areas of urban wastewaters; they are focused on the determination of bacterial inputs by wastewater treatment plants, the role of environmental factors on the enteric bacteria survival in the coastal zone, and the modelling of bacteria transport and disappearance in order to provide useful management information for minimizing faecal pollution in the coastal zone.

The main objective of this paper is to evaluate the possible relationship between urban wastewater disposal and eutrophication in the coastal zone. Firstly, nutrient loadings are studied in raw and treated sewages coming from physical-chemical and biological wastewater treatment plants. Secondly biological responses of coastal ecosystems to overenrichment are considered in term of macroalgal or phytoplanktonic proliferations. Finally it can be deduced that to assess the risk of eutrophication due to urban wastewater disposal, it is necessary a) to evaluate the form and the respective importance of urban and riverine nutrient loadings into the site, b) to determine the physical sensitivity of the disposal area by evaluating the morphological or hydrodynamical entrapment of water masses, c) to point out possible nitrogen or phosphorus limitation for primary production in a potentially eutrophicated site. All these evaluations may help optimizing a reduction strategy of nutrient coastal discharge by urban wastewater, and finding the limiting nutrient that must be controlled in the sewage treatment plant.

In order to improve bacterial water quality of shellfish farming areas, studies were conducted in the English Channel (Morlaix) and on the Mediterranean coast (Toulon). These two areas were chosen in order to compare behaviour of fecal bacteria in two different ecosystems. In the estuary of Morlaix sediments are polluted by way of settlement, but most of the bacteria are mixed with turbid waters and are able to survive a very long time (T90 are in a range of several hours to several days). By measuring the increase in salt tolerance of the strains grown in natural organic matter, it was demonstrated that Salmonella can tolerate coastal water salinities. Moreover, because light penetration is prevented by suspended matter, the solar bactericidal effect is very low. On the contrary, through lack of nutrients and very high sunlight intensity, die-off rates in Mediterranean waters are very high (at the surface T90 are less than 2 hours, and several hours in deep waters). A close relationship was found between the light intensity received by bacteria and the T90. Predicted T90 must be found using these two parameters(including turbidity and deep effect on light intensity). The authors suggest that precautions must be taken to carry out impact studies depending on water quality of the area, especially in turbid areas. The knowledge of these mechanisms is very important to evaluate waste water impact on the quality of shellfish farming areas, and to improve elimination of fccal bacteria in sewage treatment plants.

Click to increase image sizeClick to decrease image sizeModelling dissolved and particulate contaminants transport in the Morlaix estuary. Application to enteric bacteria discharge. Dissolved contaminants and cohesive sediment transport models have been developped and applied to a macrotidal estuary. These models are original as several dissolved and particulate constituents can be simultaneously computed, the later being followed in the surficial sediment according to the deposition events. Resides laboratory and field experiments have been conducted in order to evaluate the survival of enteric bacteria both within the sediment and the water body. Showing off rather long survival times especially in the sediment, the results have been introduced in the models in order to simulate the impact of urban disposal on water quality in a shellfishing area.