Discover our professions

Profession: Research director

Philippe Boët
Irstea –Estuary ecosystems and diadromous fish unit
Cestas – +33 (0)5 57 89 27 06

Whether freshwater or seawater, estuaries are multifunctional from an ecological, economic and social standpoint: they are an attractive landscape feature, they are used for fishing activities and are rich in resources and biodiversity. They are subject to numerous pressures related to human activity that endangers the future of the species that live there and which cause a reduction in the natural goods and services that these ecosystems provide to society. In order to understand how the Gironde estuary works, the laboratory equates the interactions between the various links in the food chain: algae, zooplankton, fish and also fishing activities and pumping systems. It reproduces ecosystems and simulates changes in them: oxygen reduction, temperature increase, a larger fish supply and flow reduction. It can then observe how significant pressure on one of these components can lead to a cascading imbalance in the whole system. Its objective is to identify all the essential elements involved in this process, such as shrimps, which are an important food source for many fish.

The research unit explores potential change scenarios under natural or human constraints, for possible trajectories. It identifies those changes which are favourable and those to be avoided.

L'unité explore ainsi des scénarios d'évolution éventuelle de l'écosystème sous des contraintes naturelles ou humaines, les trajectoires possibles, celles souhaitables ou au contraire à éviter.

Profession: Senior research engineer

Françoise Daverat
Irstea – Estuary ecosystems and diadromous fish unit
Cestas – +33 (0)5 57 89 08 06

Eels and salmon are unique in that they divide their lives between rivers and oceans. Studying their migration and their choice of habitat can reveal the best environments in which to preserve these endangered species. An indirect way to follow fish movement is to study their otoliths. Otoliths are the bones in the inner ear that grow regularly by accreting rings (similar to trees).

This bone matter is therefore reflective of the water composition in which fish live. It follows the same principle as sedimentary layers.

Therefore, measuring the chemical composition of otoliths can reconstruct the trajectory and growth of fish from birth to death. Certain chemical elements, which accumulate in these rings, confirm fish presence in estuarine or oceanic environments.

Profession: Senior research engineer

Alain Dutartre
Irstea – Water networks, purification and quality unit
Cestas – +33 (0)5 57 89 08 00.

Often ignored by the general public, unless their overgrowth makes them easily visible and obstructive, aquatic plants are present everywhere in freshwater environments (rivers, lakes, humid areas). Producing organic matter and home to numerous species of aquatic fauna, they play an important role in how ecosystems operate. However, they can also serve as a bio-indicator, as investigated by Alain Dutartre’s team. Whether discreet or exuberant, native or exotic, aquatic plants indicate the ecological quality and the potential for change wherever they are present. Therefore, by studying their development conditions and characteristics, the way aquatic environments are managed can be improved.

Profession: Senior research engineer

Anne Gassiat
Irstea – Amenities and dynamics of rural areas unit
Cestas – +33 (0)5 57 89 08 00

Everybody has looked at a familiar place and thought, “Everything has changed so much here, I no longer recognise it!” Companies and individuals are increasingly drawn towards coasts, rivers and estuaries, which means rural areas are cropped (forests and agricultural land) due to urban sprawl.

Institutions, groups and associations play important roles in these changes. My research is based on the theme of “earth seen from the water”. I study the changes in land use using water as a starting point (coastal, river or estuarine waters). I try to analyse how our territories and our spaces are built around water with a view to supporting public decision-making. For this purpose, I rely on existing land databases and on qualitative surveys led by these important establishments. In this way, I can gain a clearer understanding of how they view these changes and how they adapt to them, by taking into account public policy implementation.

Profession: Chief engineer of bridges, water and forests.

Yves Le Gat
Irstea – Water networks, purification and quality unit
Cestas – +33 (0)5 57 89 08 00

The laboratory provides management and consultancy tools to keep the immense heritage of these drinking water and sanitation distribution networks in optimal condition. Yves Le Gat’s modelling work predicts the changes in water pipe breakage and sewer damage. Equations enable him to “see” these underground networks which are normally so difficult to access.

In order to evaluate them, a perfect knowledge of the materials is required, as well as the diameter, lengths and other parameters of this network that is so vital to our cities. This knowledge helps to formulate and to compare, in the long term, different scenarios for network rehabilitation. Authorities can then choose those that guarantee the best relationship between network performance and the most reasonable rehabilitation costs.

Profession: Senior research engineer

Nicolas Mazzella
Irstea – Water networks, purification and quality unit – Water chemistry laboratory – Irstea
Cestas – +33 (0)5 57 89 08 00

These days the DDASS (French Department of Health) and water agencies use a technique known as grab sampling to investigate aquatic environments. This method, despite being inexpensive and easily implemented, has a major fault: it only indicates the water quality at the given moment when the sample is taken. However, over the past fifteen years, another approach has emerged.

This consists of using devices in the water that continuously trap pollutants and can obtain an integrated measurement of concentrations over time, with an insignificant overhead compared with grab sampling. Nicolas Mazzella and his team are concerned with pesticide water pollution. In order to do this, he analyses the samples taken by these new devices and in collaboration with hydrobiologists and ecotoxicologists, he studies the exposure of pesticides to aquatic organisms, as well as the toxicity of these pollutants.

Profession: Geomatician

Kévin Petit
Irstea – Amenities and dynamics of rural areas unit
Cestas – +33 (0)5 57 89 26 98

How do you find your way? What is the population density of Tokyo? How are water resources distributed in Africa? We handle more and more geographical data today, data that we can locate on the globe. All “objects” (a city, a piece of land, a road, etc.) can be referenced and displayed geographically because they have latitude, longitude and altitude.

In his laboratory, Kevin Petit is responsible for collecting, organising, processing, analysing and restoring these geographical data in map form. This work can assist numerous researchers in all domains: agriculture, environment, economics and sociology. As it is like a drawing, the map makes us see information directly and intuitively that would be difficult to understand or conceive by reading a few sentences.

Don’t we say that a picture says a thousand words?

Therefore, maps are a very powerful tool for discussion and decision-making.

Profession: Research director

Yvan Racault
Irstea – Water networks, purification and quality unit
Cestas – +33 (0)5 57 89 08 00

The team works on optimising wastewater treatment processes. It is particularly concerned with a technique that combines activated sludge with membrane filtration to produce high quality purified water. This concept consists of adding oxygen to the bacteria already present in wastewaters in order to promote their survival and development. They feed on substrate waters and transform organic matter into biomass (sludge) and into CO2. The organic membranes immersed in the mud ensure a very fine water filtration (10,000 times smaller than a millimetre) preventing microorganisms, such as bacteria. The filtered water is of a very high quality, it can be released into the most sensitive environments and can even be reused for agriculture or re-injected into the soil to provide ground water.

 This type of process, which respects water management, is growing in popularity. By modelling the biological and physical processes taking place in this processing, Yvan Racault and his team aim to improve the understanding of mechanisms and to simulate operations scenarios in order to test different design strategies and installations management.

Profession: Research associate in environmental economics

Tina Rambonilaza
Irstea – Amenities and dynamics of rural areas unit
Cestas – +33 (0)5 57 89 08 00

The team concentrates on society’s latest expectations with respect to space and rural areas. There are 65 million French people and they all want their own private space (main home or second home) and often in those places that allow them to benefit from natural surroundings without being too far from a city. This obviously poses problems. Firstly, for ecological and environmental issues: population density and their activities bring about pressure on natural environments which can compromise their ecological stability and damage the environment (pollution, landscape degradation). However, there are also economic and social issues: an increase in demand for housing causes a surge in property and land prices and means that people of certain social categories are unable to live in these areas.

By using surveys and data from readily available statistical census documents, Tina Rambonllaza aims to understand the changes in rural areas caused by urban expansion. In addition, she puts forward ideas for reflection regarding the sustainable management of these changes.

Profession: Doctoral student

Valérie Samedy
Irstea –Estuary ecosystems and diadromous fish unit
Cestas – +33 (0)5 57 89 08 00

Do you know that you can detect and study fish by locating the echo that they transmit?

This is known as fisheries acoustics and focuses on living aquatic resources. This innovative technique, which has the advantage of covering large geographical expanses, is used in areas that are not suitable for conventional fish sampling and does not harm the environment or the fish studied.

Valérie Samedy develops this technique for estuaries by comparing nature and the characteristics of acoustic signals detected with the biological reality. She leads the Gironde Acoustic Fishes (GAF) campaigns that will establish a research strategy to suit the environment and will produce a standard sampling and monitoring protocol. The objective is to meet the demands of future regulations, which will impose more and more ways to observe and measure, such as bio-indicators, without harming fish fauna.