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L'Etang de Berre est un écosystème eutrophe qui reçoit de l'eau douce et des nutriments par deux rivières et par la Durance via la centrale hydro-électrique de Saint Chamas (SC). En intégrant les variations horaires, les échantillons journaliers nous ont permis de calculer un bilan annuel représentatif des apports en nutriments : SC apporte 1085 tonnes de N total (93 % est équi-réparti entre les formes nitrates et azote organique dissous) et 30 tonnes de P total (80 % est sous forme particulaire) sur la période Octobre 2008 à Novembre 2009. La fréquence d'échantillonnage requise pour obtenir le flux annuel en N total avec une erreur de 25 % est mensuelle. Pour le flux annuel de P total, l'erreur minimale est obtenue à partir de l'échantillonnage le plus fréquent testé (i.e. hebdomadaire) mais varie entre -30 % et +60 %. Si on compile toutes les études, on observe que les apports en nutriments à la lagune ont diminué ces 2 dernières décennies. En 2006, SC représente 50 % et 14 % des apports allochtones en N total et P total respectivement. Les sources diffuses et atmosphériques et la labilité des fractions organique dissoute et particulaire restent à préciser.

When placed in a Hele-Shaw cell and submitted to a uniform magnetic field, a suspension of superparamagnetic particles self-organizes into a 2D array of columns with hexagonal order on short distances and glasslike order on long distances. Such arrays were usefully used for fast electrophoretic separation of long DNA molecules. Although self-assembled matrices have the advantages of simplicity and tunability, it is impossible to have the precisely controlled order and pore size obtainable in a microlithographic array. We address the latter challenge here. A magnetic nickel template is prepared on one cell surface by lift-off. Under a uniform external field, the nickel dots create local magnetic field gradients that attracts the beads, imposing a predefined order. We demonstrate the ability to separate long DNA molecules with these matrices and achieve the first steps of studying the resolution of the DNA separation over a wide range of posts density.

Hydroecology (or aquatic ecology) is the study of aquatic systems in their three interacting aspects: physical, chemical and biological. The creation in 1974 of the Environment Department at EDF Research and Development Division marked the start in France of quantitative hydroecology applied so power generation installations. The studies developed around several main themes, determined both by the expansion of the nuclear power programme and by changes in French environmental regulations, in particular the 1976 law on impact studies, the 1984 fishing and hydrobiology law and the 1992 water law.In this framework, the effect of artificial warming of rivers, eutrophication of continental and marine waters, transfers of mineral micropollutants and radionuclides in rivers, and problems specific to hydropower installations such as guaranteed instream flow or fish pass design, have been studied. This work, conducted in collaboration with many other research laboratories, has led to the development of original quantitative approaches, notably in the field of numerical modelling. The paper selects several of the tools developed whose scope of application is wider than the environment and management of thermal or hydropower plants. Two major applications grouping the experience acquired in hydroecology are presented: the AGIRE software and the global environmental study of the Singrauli area in India.

A first version of a digital model of a coastal ecosystem developped in North Brittany between Roscoff and Saint-Brieuc is described. Designed for impact studies and taking into account a meterological time scale of over 20 years, this model simulates the daily changes in water temperature, salinity, phytoplanktonic biomass and nitrogen, with spacing of 2 km. After indicating the principal adjustment phases of the model and actions planned to improve its descriptive quality, an application of the latter is given showing possible consequences of nitrogen from the coastal rivers, in an agricultural region with heavy use of fertilizers, on the development of marine phytoplankton.

In many big rivers at the low-water mark major phytoplankton or microscopic algae development can be seen living and being moved along by the current. Unlike what is seen in many lakes at the end of Spring this algae development does not usually exhaust the stock of easily assimilated phosphorus contained in the water. Thus phosphorus is not a factor that limits the growth of phytoplankton and this is why we have the proliferation of plant life if other nutrients are not lacking. Since digital modelling is capable of taking into account hydrometerological conditions over several years it is an efficient instrument for assessing the reduction of waste being introduced into the catchment area that is necessary in order to obtain limiting conditions. Applications are given for the Doubs and the Moselle rivers for which we show that a large scale dephosphatization effort would be required in order to achieve a major reduction in the concentration of phytoplankton.