Ecological diagnosis: how healthy are our rivers and streams ?

How can we assess the ecological condition of our rivers and streams ? Since 2012, the Seine river basin has been the subject of an ecological and ecotoxicological monitoring pilot study. Irstea researchers are using a range of regulatory and innovative tools to comprehensively and concretely assess the quality of the watercourses studied. Below we take a look back over some images from the most recent sampling campaign.

Human activities are undermining the balance of aquatic ecosystems, and several complementary approaches are available to identify these disturbances :

  • establish an overall picture of chemical and ecological quality using measures proposed by the European Water Framework Directive (EWFD).
  • determine ecotoxicological indicators that can make the link between changes in the environment and impacts on aquatic organisms.

Specialists in ecotoxicology research, a team of researchers at the Irstea Antony center launched a pilot study [1] in 2012 to evaluate the quality of rivers in the Seine-Normandy river basin. 20 sites from among the monitoring stations of the Seine-Normandy Water Agency (AESN) were selected, all with different pollution gradients (presence of nutrients, micropollutants, etc.). With the in situ installation of a network of sensors during the summer of 2012, continuous monitoring for 3 years of the temperature and water level at these sites has been possible. In addition, successive rounds of measurements were performed, as well as three annual sampling campaigns.

Biomarkers + bioindicators = ?

The objective of this study is to combine different tools : some used in EWFD networks (bioindicators, chemical measurements), and some developed by research teams to estimate the effect of contaminants on aquatic organisms (biomarkers) and improve the description of chemical risk (passive samplers and bioassays). Tools designed independently, but which, once combined, could provide an overview of the health of aquatic ecosystems and waterways.

Focus on the work of researchers in the field, during a sampling campaign at the Chalmaison and Courtomer sites in Seine-et-Marne.

© Irstea

Water samples to measure oxygen, temperature, conductivity, and the mineral composition of the water (calcium, sodium, magnesium, etc.).

Total and dissolved concentrations of metals, non-biodegradable contaminants, are also measured.

© Irstea

 

Weighted cages being installed in the water. Inside are rows of plastic sheets on which biofilm is deposited, or in other words everything suspended in the water (bacteria, microorganisms, etc.).

This is one way of analyzing microscopic aquatic life.

 

© IrsteaDeployment of passive samplers: sensors are installed on the outside of the cages, in order to estimate the concentration of labile metals present, or in other words the percentage of mobile metal in the aqueous medium. The sensors are made of a resin that attracts metal and a gel that allows their diffusion towards the resin. The metals are then collected in the sensor. These tools are robust.

This type of monitoring is proving to be much more accurate. Indeed, spot measurements do not allow assessment of the potential impact on organisms, as they do not allow for the notion of effects over time.

 

© IrsteaCages of scuds calibrated by size (a small shrimp known to bioaccumulate metals and organic contaminants and used by researchers as a bioindicator). Each cage contains several vials of scuds with a food source (Alder leaf).

After a week of exposure in situ, researchers retrieve the scuds and count them in order to estimate their survival rates, feeding behavior, etc. The levels of metals accumulated in their tissues will also be determined in the laboratory.

Some "wild fishing" was also performed: indigenous scuds were collected at each site. Internal metal content will be compared to that of the caged organisms. In this way different biomonitoring methodologies (active and passive) can be compared.

Results

The data collected during the three annual sampling campaigns (2012-2014) will provide researchers with a more representative picture of the quality of the watercourses studied, and allow them to improve diagnostic tools so that they can help guide water managers in deciding future actions. Results are expected in 2015.

The Seine river basin in figures

The Seine river basin :

  • occupies 12 % of the national territory
  • sustains a quarter of the French population
  • a third of its agricultural and industrial production
  • and more than half of its river traffic.

The basin is well-suited to the launch of such a pilot activity (as it sometimes has high levels of river eutrophication and a large number of facilities altering the hydrological connectivity, etc.).

For more information

[1] BioMArqu’Indic Project, started in 2012. Started within the framework of PIREN-Seine, the project is funded by the Seine-Normandy Water Agency (AESN). Project led by the Irstea Antony center. Irstea involvement: HBAN (BELCA team + QUASARE + BELCA - Lyon). Partners: University of Reims (Animal-Environment Interactions unit), University Paris-Sud (SPE Group-JRU 8079 CNRS - AgroParisTech), University of Bordeaux I (LPTC-JRU EPOC) and the company Vigicell.