Trois groupes de paramètres pour suivre la qualité des milieux aquatiques

• Nitrogen and phosphorus nutrients originate from agricultural, industrial, or urban sources. They can result from excessive use of mineral or organic fertilizers (manure spreading), industrial or domestic discharges (use of phosphate-enriched detergents to soften water). Such discharges promote algae development in aquatic environments and deplete dissolved oxygen. These pollutants ultimately disrupt biological balances; • Pesticides include phytopharmaceutical products used primarily in agriculture (insecticides, herbicides, fungicides…) and biocidal products (household disinfectants, anti-fouling paints…). These substances or their degradation products can have acute and/or chronic toxic effects on ecosystems as well as on humans;

• Metals (copper, lead, cadmium…) present in aquatic environments may be of natural origin or come from industrial, agricultural, or urban discharges. Their hazard level varies greatly depending on their nature; • Other organic or inorganic compounds come from industrial discharges, service sector activities, and households. Examples include polycyclic aromatic hydrocarbons (PAH), chlorinated solvents, dioxin-type compounds, pharmaceuticals… These substances can reach waterways through wastewater treatment plants or after being released into the atmosphere.

Some of these chemical parameters have undesirable effects for humans or the environment at very low concentrations ("micropollutants" when these concentrations are around one microgram per liter), while others act at higher concentrations ("macropollutants").

Animal and plant species are bio-indicators of aquatic environment quality.

The composition and abundance of four species groups are monitored: diatoms (microscopic algae), macrophytes (aquatic plants visible to the naked eye), invertebrates (insects, crustaceans, mollusks, worms), and fish.

Physical parameters characterize notably suspended matter or sediments present in waters (volume, mass, size, percentage…) and conditions affecting the development of aquatic fauna and flora such as temperature and turbidity.