Notenboom Jde Boom Kvan Beelen P2017-02-201990-06-30The purpose of the study is to obtain a better knowledge of organisms occuring in the upper layers of phreatic groundwaters and to get an indication of the environmental variables determining the structure of their communities. A sampling program has been carried out of bore holes situated in alluvial and diluvial, sandy and gravelly aquifers. The groundwater fauna of the samples consist of Protozoa, Tardigrada, Rotifera, Enchytraeidae, Nematoda and Crustacea. A multivariate analysis of the data showed that the abiotic factors: acidicity, electric conductivity, calcium content and groundwater stage are slightly correlated with the structure of the communities. These factors might be related partly with the food supply and oxygen availability in the uppermost groundwater. The harpacticoid copepod Parastenocar seems to be rather common in upper sandy and gravelly aquifers and it appears to be a suitable test and indicator organism in groundwater ecotoxicological studies. Other groups of organisms probably of importance as bioindicators for groundwater pollution and disturbance are the Nematoda and Rotifera.<br>104 pnl13grondwaterecologielevensgemeenschappenmeercellige organismen; grondwaterecotoxicologieReport2017-02-20