The key objective of this work package is the comprehensive representation of groundwater fauna biodiversity of the sites selected in WP1. On one hand, the diversity will be surveyed in a classical morphological way to ensure a reference to the previous biodiversity data (Stein et al 2012; 10.1038/srep00673). In addition, these data are used to cross-reference with aquifer eDNA data. Water from the aquifers of the selected sites (WP1) will be filtered, DNA isolated, sequenced, and matched with reference data (public databases and internal databases) to identify the species present. This procedure was tested for the first time and applied on a large scale in the BMBF project Bio-TGW. The first results indicate that these two methods complement each other excellently. Furthermore, there is an opportunity to further develop the eDNA techniques as a very effective monitoring tool.

The data collected in WP4 will serve as the basis for integrative groundwater quality management (GQM) and will be a key contributor to the social-ecological assessment of the place value of groundwater ecosystems in WPs 7 and 8. In addition, the association of environmental data, bioassays, and community species composition will describe a number of fundamental ecological issues of groundwater habitats for the first time:

• What are the ecological requirements of groundwater species that have scarcely been studied so far?
• How do groundwater species differ in their vulnerability with respect to specific environmental stressors?
• Which chemicals detected in the environment are significant for the ecosystem?
• Which of the descriptively determined correlations between community species composition and chemical data can be experimentally validated?