Identifying pressures to take better action: the ORION approach

Identifying where rivers are suffering in order to choose the right actions

ORION is a cross-border project (France–Wallonia–Flanders) that aims to diagnose the state of rivers and water bodies in the Meuse basin and predict how they will evolve so that action can be taken in the right place at the right time.

Researchers are monitoring three types of signals: chemical (pollutants), microbiological (viruses, parasites and antibiotic resistance) and ecotoxicological (responses of living organisms), all in the context of global warming. In concrete terms, the project seeks to identify the constraints (referred to as ‘pressures’) exerted on water bodies, how organisms react to them, and what this implies for bathing, biodiversity and resource management.

What progress has ORION made in the last six months?

During the first half of 2025, under the coordination of the University of Reims Champagne-Ardenne (URCA), the six operators (universities, laboratories and technical institutes) discussed, in particular, the development of common protocols to ensure the complementarity of the tests and guarantee their scientific value.

The aim of the first few months of the project was not only to agree on the protocols of interest, but also on the sites to be studied. In this context, the teams at the PeGire laboratory (ULiège) gathered the information needed to construct pressure maps showing where and when the river is most likely to be impacted.

Among the various chemical pressures on the Meuse basin, PFAS, nicknamed ‘forever chemicals’ because of their high persistence and resistance to natural degradation, are widely found. They are therefore the focus of attention for the project's researchers. To address this issue, ISSeP has validated a method for analysing these substances in surface water and will extend it for this project to sentinel species (living sensors that are particularly sensitive to these molecules or likely to store them). The aim is to compare what is measured in water with any accumulation in organisms. This is a key step in assessing ecotoxicological risks: this link between water and living organisms is essential for assessing hazards and deciding where to take priority action.

The project is also looking at two other families of molecules. Firstly, PAHs, molecules composed of a network of carbon atoms, produced during incomplete combustion due to low oxygen levels (domestic heating, exhaust fumes from combustion engines, industrial activities, etc.). As such, they are not harmful, but when the liver tries to get rid of them, to metabolise them, the compounds produced are carcinogenic. It is like a harmless glass marble which, once broken, becomes dangerously sharp. The other molecules studied are phthalates, which are added to plastics to make them more flexible. They are present in a large number of flexible everyday objects and, unfortunately, their bond with plastic is fragile, meaning they are widely dispersed in aquatic environments. And while they are biodegradable, this process is facilitated by the presence of oxygen: once in water, their persistence becomes problematic. Phthalates are classified as endocrine disruptors: they can interfere with the proper functioning of internal hormonal messages in living organisms, particularly those related to reproduction (known as reprotoxicity).

Several tools are used to determine whether water contains elements capable of disrupting living organisms:

• Biological screening tests: genetically modified yeasts are placed in water samples after periods of heavy rain. If they change colour, this is evidence of abnormal hormonal activity in the water that warrants further investigation.    Animals in the environment are key indicators, as some absorb chemicals and are unable to eliminate them effectively from their bodies. PAHs and phthalates in particular have an affinity for fats, easily binding to them and persisting in living tissue. As a result, living organisms gradually accumulate these substances, a phenomenon known as bioaccumulation. Analysing organs and blood allows us to link pollutant concentrations in water to their presence in aquatic organisms.
• The measurement of vitellogenin (or VTG) in fish is a biomarker, i.e. a specific biological response, and monitoring it enables the early detection of endocrine disruption. This protein, normally produced by females to transport the lipids needed for egg formation, can, for example, appear abnormally in males after exposure to hormonal substances present in the environment.
• Sperm motility, or the ease with which spermatozoa move, is also assessed. Even under normal conditions, a significant proportion of these reproductive cells are defective and their locomotion is reduced, which is not surprising given the huge number of cells produced. Endocrine disruptors can, among other influences, increase the frequency of these defective cells and thus impair reproduction.
• Another biomarker to be measured, this one immunological, is phagocytosis. This is the process by which certain living cells are able to engulf and break down foreign particles (bacteria, cell debris, etc.). In the laboratory, immune cells are placed in contact with foreign elements (in this case, tiny latex beads) to gauge their reactivity and effectiveness in ingesting them. This reveals the impact on the immune response, or immunotoxicity, of substances present in the environment.

✨ The ORION approach is to 

1. Identify/See: combine chemistry, microbiology and ecotoxicology, multiply approaches to obtain a reliable picture of the pressures and vulnerabilities of water bodies.
2. Understand: use predictive modelling to anticipate the effect of discharges, weather events and climate on rivers. Like weather forecasts: this involves observing the behaviour of a system in order to reproduce it artificially by simplifying it (i.e. creating a dynamic model) in an attempt to predict its future behaviour.
3. Act: testing scenarios (‘what if...?’) to help managers and decision-makers choose the most effective measures.

In concrete terms, what is ORION used for?

• Anticipating risks to water potability: although ORION is not directly involved in drinking water distribution, the project's study of the pressures on rivers provides managers with tools to prevent risky situations before water is collected and treated.
• Ensuring bathing water quality: by combining chemistry, microbiology and biological responses, the project helps to focus monitoring on sensitive bathing sites during periods of use (particularly in summer).
• Preserving biodiversity: climate-related heat waves, droughts and floods alter the habitat of aquatic species. ORION's datasets and biological tests make it possible to quantify these effects locally in order to better target the measures to be taken.

In short

The first half of the year laid a solid foundation combining operational governance, the completion of analytical methods, initial structuring data sets, successful ecotoxicological tests and public engagement. This forms the basis for an integrated diagnosis involving managers, scientists and citizens alike.

Water: everyone's business

The ORION project was highlighted at the Printemps des Sciences in Namur (March 2025), in the presence of regional authorities, and then at the Assises Rhénanes de l'Eau in Strasbourg, where the project was cited as a good cross-border practice. Two exhibitions — Sentinelles en eaux troubles (Sentinels in troubled waters) and Qu'arrive-t-il à la rivière de Gammarus ? (What is happening to the Gammarus river?) — welcomed more than 500 visitors to UNamur.

What next?

Autumn 2025 will mark the launch of the prospecting phase for caging sites, a key step in preparing for the field campaigns that will take place from spring 2026 onwards. These visits will enable the selected sites to be identified and validated, their accessibility and hydrological conditions to be assessed, and the installation of caging devices for sentinel species to be prepared.

✨ Who does what?

ORION brings together universities, public laboratories, agencies and water managers from France, Wallonia and Flanders. This alliance enables the cross-referencing of field data, laboratory tests and modelling tools to produce comparable results on both sides of the border.

• University of Reims Champagne-Ardenne (URCA): general coordination and aquatic ecotoxicology (governance, testing and biomonitoring).
• University of Liège – PeGire Laboratory: data, pressure maps and pressure-impact maps for the Meuse and its tributaries.
• Public Service Scientific Institute (ISSeP): PFAS metrology (surface water), chemical characterisation and adaptation to biota, YES/YAS and VTG tests.
• National Institute for Industrial Environment and Risks (INERIS): ecotoxicological testing and biomarkers under controlled and field conditions, biota modelling.
• University of Namur – Environmental and Evolutionary Biology Research Unit (URBE): ecophysiology and ecotoxicology of fish – Confluent des Savoirs (CDS): dissemination and popularisation of the project.
• ACTALIA: bacteriology, virology & parasitology (in water and in a sentinel species).

FAQ

What is bioaccumulation? It is the process by which a living organism stores a chemical substance, such as a pollutant, in its body tissues. This means that the living organism is unable to eliminate it effectively. The result is an increasing concentration of the substance in the organism compared to its environment, which can become toxic over time. Bioaccumulation occurs via the environment and food.

What is a biomarker? A biomarker is a measurable biological indicator (e.g. a protein or hormone) present in the body (blood, mucus, tissue, etc.). The measured level acts as an alarm signal, allowing analyses or measures to be prioritised before the toxicity has more significant and irreversible consequences.

What are PFAS? These are artificial molecules created for their resistance and ability to repel not only water but also fats. PFAS is the acronym for ‘perfluoroalkyl and polyfluoroalkyl substances’. These molecules resemble matchsticks: a chain of carbon atoms of varying lengths, partially or completely covered with fluorine atoms, with a head at the end of the chain that can have different properties. PFAS are very difficult to destroy, as they have been designed for their resistance: carbon-fluorine bonds are among the strongest there are.

What are PAHs? This is the acronym for Polycyclic Aromatic Hydrocarbons, molecules that form after incomplete combustion, i.e. in an oxygen-poor environment. They are found in smoke, soot, exhaust fumes, barbecues, etc. Some are known to be carcinogenic, which is why it is not recommended to eat food that has been charred during cooking.

What are phthalates? They are synthetic molecules added to plastic during manufacture to make it soft and flexible: they are plasticisers. They are everywhere around us: shower curtains, flooring, packaging, beauty products, nail varnish, etc. The problem is that they are not chemically bonded to the plastic and can therefore easily escape over time. Some are suspected of being endocrine disruptors.

What is an ecotoxicological risk? It is the probability that living organisms will suffer adverse effects as a result of exposure to a pollutant resulting from human activities. It depends both on the amount of the substance present in the environment and on the sensitivity of the organisms exposed.