The effects of climate change pose an ever-greater threat to our groundwater because more frequent and longer periods of drought reduce groundwater levels. Groundwater is therefore already supplemented with surface water in conurbations like the Rhine-Main area. This surface water often contains treated wastewater that may add pollutants to the groundwater. More frequent heavy rainfalls - another consequence of climate change - lead to large quantities of pollutants entering the groundwater. As a result, over one third of all groundwater bodies in Germany fail to achieve good chemical status. The European Water Framework Directive establishes the legal framework for assessing the quality of groundwater. However, a "huge amount of investigation" into the groundwater quality is still required, according to Professor Henner Hollert from the Institute of Ecology, Diversity and Evolution at Goethe University Frankfurt. Chemical analyses have identified at least some of the pollutants in the groundwater, including drugs, pesticides and perfluoroalkyl substances (PFAS), which originate from the wastewater, traffic or agriculture. "What we don't have at all is effect-based data, i.e. data about how the pollutants impact life in the groundwater ecosystem and also human health. We already know a lot about surface water, but not about the groundwater."
The project "Ecological and Ecotoxicological Groundwater Quality Monitoring based on an Integrative Triad Approach" (gwTriade) is now set to plug that knowledge gap. The triad approach combines three different scientific pillars: chemical analyses, bioassays and studies of biocenosis, i.e. the interactions between organisms living in a certain habitat. The crucial aspect is that results from the three measuring methodologies are combined into an overall result - only when this has been done can the ecological status be comprehensively assessed. "We are the first to apply the triad approach to groundwater," Hollert stresses. "It gives us a good overview. We can see what pollutants are present in the groundwater, and how they affect organisms and biological systems - both under laboratory conditions and in the field."
Six institutes are involved in the project and the tasks are shared among them. Hollert and his colleague Dr. Sabrina Schiwy coordinate gwTriade and conduct tests using a battery of bioassays that was also recently put forward to the European Commission for environmental monitoring. The testing systems are cell culture systems, zebrafish embryos, algae and Daphnia (tiny water fleas). Schiwy explains how Daphnia is used: "First of all we test the effects of the pollutants in the unaltered groundwater samples. Next, we dilute the groundwater samples and thus the concentrations of pollutants, and observe what happens. In this way we discover which dilutions of groundwater pollutants cause which effects in Daphnia." For example, if a substance with reproductive toxicity is present, the water fleas do not multiply as much as they normally would. In zebrafish embryos neurotoxic effects may occur, i.e. disruptions of the nervous system that lead to a change in behavior. "Zebrafish have a typical pattern of swimming behavior," Schiwy explains. "If it's light, they show relaxed behavior. If it suddenly gets dark, they swim in hectic zigzags." The reason is that the sudden appearance of a shadow could mean a predator is approaching. To see in the lab whether the fish larvae display this normal behavior, they are exposed to an alternating regime of light and darkness in a special experimental set-up. If the fish do not react, this is an indication that pollutants might have impaired their nervous system. If the researchers suspect this, the neurotoxic effect is characterized in detail using methods from molecular biology. The behavioral tests are not solely about ecotoxicological aspects, Henner Hollert adds, but are also relevant to human toxicology. Studies involving the early stages of zebrafish - an alternative to classical animal experiments - are also an established model in environmental medicine. "Zebrafish are vertebrates, which means that the results give indications about possible effects in human beings. We can draw conclusions for the protection of human health."
To supplement the bioassays in Frankfurt, chemical analyses are also performed by the IWW Water Centre in Mühlheim an der Ruhr and the Zweckverband Landeswasserversorgung (state water supply association) in Langenau. The IWW analyzes the PFAS contamination in particular and also investigates the geosystem. This generates a geochemical, hydrochemical and hydraulic description of the sites where the groundwater samples are taken. The third type of investigation is undertaken by the University of Kaiserslautern-Landau (RPTU). It examines the composition of the groundwater fauna, which includes Cyclops and rotifers, for example, using taxonomic methods and modern methods from molecular biology. With e-DNA analyses and metabarcoding it is possible to detect genetic fragments of all living creatures that have lived or currently live in the water. This enables research into the composition of the entire community of living organisms in the groundwater. The Institute of Groundwater Ecology (IGÖ) in Landau provides support here with its expertise in groundwater ecology and especially in identifying new groundwater organisms for bioassays.
The gwTriade scientists are not only interested in examining certain selected sites. They want to develop a concept for the integrative assessment of the groundwater quality for regional and national bodies throughout Germany with responsibility for groundwater, such as water suppliers and nature conservation authorities. Hollert says, "Our assessment system gives them a guide to how they can apply the methods for monitoring groundwater quality - and to how the data collected can be examined and put into context." The task of finding potential users and clarifying their needs is assumed by the Institute for Social-Ecological Research (ISOE) in Frankfurt. It also tries to identify use conflicts relating to groundwater that could occur in the future, for instance between using groundwater as a resource and protection of the ecosystem. From a biological viewpoint, according to Hollert and Schiwy, groundwater is also a habitat. It's just that until now this perspective has not received enough attention.
Background: gwTriade: Ecological and Ecotoxicological Groundwater Quality Monitoring based on an Integrative Triad Approach
https://bmbf-lurch.de/lurch/en/Joint+projects/Joint+projects/gwTriade.html
Images for download:
https://www.uni-frankfurt.de/146261494
Caption: A copepod is a crustacean barely a millimeter in size which lives in groundwater. The presence of such animals is an indicator of good water quality. Photo: Sabrina Schiwy, Goethe University Frankfurt
