Ecotoxicology

Ecotoxicity Network

In the context of the Water Framework Directive (2000/60/EC), the main industrial or urban effluent are studied in detail using a battery of tests to assess the capacity of the receiving waterbody  to dilute the toxic load. The water body is the unit for assessing whether or not environmental objectives have been met, introduced by the Water Framework Directive. This is where objectives are set and the risk of not achieving them by the end of the management plan is assessed. It is also at this level that the environmental effectiveness of the measures (actions) taken by managers is assessed. The aim of investigative control is to determine the cause of non-achievement of objectives, and bioassays are particularly suitable tools in this context. Since 2005, the Walloon Region’s surface water ecotoxicity network has been adapted to meet these new requirements, focusing on waterbodies requiring more in-depth study in order to better understand pressure-impact relationships. In this context, the Ecotoxicity Unit :

• Measures the toxicity of industrial effluents and receiving surface waters (upstream/downstream of emission);
• chooses the tests which, grouped in batteries, are best able to describe the toxicity of effluents from specific industrial sectors;
• studies the capacity of rivers to dilute the toxic load brought by these industrial effluents;
• applies these tests as a tool for monitoring effluent treatment efficiency.

In addition, every 5 years, the test battery is routinely used at around 30 stations in the Water Framework Directive monitoring network (five-year network).

Sediment toxicity

Sediments are the ultimate reservoir for many point source (industrial or urban effluents, disused economic sites) and non-point source (agricultural pesticides) polluents. They are thus the “memory” of contamination. Conversely, they can also be a source of contamination. Bioassays are very useful for assessing the actual state of sediments in which both known and unknown contaminants are present at concentrations sufficient to cause toxicity to the test organisms. The combination of three assessment methods (chemical, bioassay and ecological – the “triad” approach) provides an answer that could not be given by any of the methods taken individually. The Ecotoxicology Unit :

• performs whole-sediment tests with sediment-dependent organisms;
• applies a battery of aquatic ecotoxicological tests on pore water and sediment leachates.

Endocrine disruption

Endocrine disruptors, as defined by the WHO, are exogenous substances that alter the functions of endocrine systems, thereby causing adverse effects on organisms and populations.

Endocrine disruptors are substances with a wide variety of structures. They include a wide variety of chemical classes which make systematic research and study difficult, hence the interest for these categories of substances in using effect-based tools in a screening approach to guide chemical monitoring.

The bioassays used by the cell are the YES (Yeast Estrogen Screen) and YAS (Yeast Androgen Screen) tests. These mechanistic tests, using yeast genetically modified by the insertion of the human estrogen and androgen receptor, enable (anti)-estrogenic (YES) and (anti)-androgenic (YAS) activity to be quantified.

Biota contamination

To meet the obligations of the Water Framework Directive and its daughter directives, member states are required to assess the chemical status of surface water bodies. Within this framework, certain Environmental Quality Standards (EQS) have been set for biota (fish, invertebrates) by Directive 2008/105/EC and Directive 2013/39/EU.
In order to meet these challenges, the Ecotoxicology Unit monitors surface water bodies on the “biota” matrix, in particular with regard to the sampling of organisms (fish and invertebrates), the preparation of samples for analysis (dissection, pooling, freeze-drying, etc.) and the detection of priority substances to check compliance with EQS. In addition, invertebrate caging techniques are also deployed as part of this monitoring network. Caging is an alternative method to organism sampling, particularly at sites where the species of interest are absent.

Toxicity of chemical substances

Bioassays on chemical substances are carried out to support the examination of environmental samples (completing the database, setting limit conditions), to assist companies in quantifying the toxicity of formulations by means of simple tests, and to evaluate and develop test systems (comparing the responses of different test systems).

Monitoring based on the effects and modes of action of certain families of substances: biomarkers on sentinel species

The Ecotoxicology unit uses the Gammaruspulex as a model species for biomonitoring. Indeed, the use of gammarids offers a number of advantages: they are abundant in many watercourses and have a very wide distribution in Europe, they are sensitive to many pollutants but sufficiently resistant to survive when these pollutants are present in the environment, their life cycle is entirely aquatic and, moreover, numerous bibliographical studies are available on their subject. They can easily be caged in situ using populations of organisms from reference sites. In addition to the quantification of bioaccumulable substances (PAHs) in this biota, this organism is also used for the determination of two biomarkers: acetylcholinesterase (AChE) which detects the exposure of aquatic organisms to inhibitors such as neurotoxic pesticides (organophosphates and carbamates) and glutathione-S-transferases (GSTs) which are involved in the phase II detoxification of hydrophobic xenobiotics (PAHs, PCBs, pesticides, ….). Other enzyme activities will be used as biomarkers in the near future to complete the tool. The feeding rate of gammarids is also monitored during caging or in the laboratory. This parameter is in fact inhibited by a wide range of contaminants (heavy metals, biocides, drugs and other organic compounds) and therefore provides information on the health status of individuals and therefore of the environment.

Bioindication based on macroinvertebrates and their biological, physiological and ecological traits for a triad approach

The complementary use of bioindicators based on the composition of macroinvertebrate communities (inventory of taxa present and their abundance in order to develop a triad approach) provides a global (holistic) view of the state of the rivers investigated. Indeed, taken separately, each of the components making up the triad (chemical analyses, effects-based methods, population impact studies) provides relevant but incomplete information. On the other hand, combining the three approaches and relating the results obtained from each of them allows us to better understand the impact of the pressures exerted at a given station, by highlighting the factors that most affect the quality of the ecosystems under consideration. This will make it possible to identify with greater certainty the causes of ecosystem deterioration (the weight of evidence) and to act more effectively to reduce the impact on the ecosystem. Developments in the synthetic analysis of biological, physiological and ecological traits of taxa open up interesting prospects for describing and interpreting the structure and functioning of aquatic ecosystems, and for assessing their biological quality.

Quality assurance

The ecotoxicology laboratory is ISO 17025 accredited for several parameters (Belac Accreditation Number: 060-TEST-ISO17025). Studies and tests are carried out to international standards.

In addition, the Ecotoxicology unit has the infrastructure and skills to implement a series of test kits:

• Phytotoxkit™
• Algaltoxkit F™
• Daphtoxkit™
• Rotoxkit F™
• Ostracodtoxkit™
• Spirodellatoxkit™

This range of choices enables the use of a battery of tests covering a spectrum of ecological functions and different sensitivities.