Department Environmental Toxicology

Fish biomonitoring of waste water effluents


Effect-Assessment of wastewater effluents by molecular biomarkers in fish

The identification and monitoring of chemical effects in organisms exposed in the environment is based on an array of approaches and specific endpoints. However, many of the existing tests have been established for only a few model organisms. Accounting for the variety of species and their different responses to environmental stressors is still a big challenge for ecotoxicological risk assessment. mRNA expression analysis of selected biomarker-genes is a promising approach for field monitoring of non-model organisms because it can capture a wide spectrum of responses of organisms to chemical exposure.  

Our project is a part of large frame project “EcoImpact” (link to the EcoImpact-project) which aims to investigate how micropollutants from wastewater influence stream ecosystems. We established biomarker gene sets for brown trout (Salmo trutta) and rainbow trout (Oncorhynchus mykiss) to assess the effects of micropollutants (such as pharmaceuticals, pesticide etc.) in fish.  A typical biomarker set consists of 20-30 specific genes which reflect different cellular stress responses like gerneral-, metal-, oxidative stress, biotransformation, immunregulation etc.. The transcriptional regulation of these genes is measured in liver and kidney tissue samples of wild brown trout caught downstream and upstream of a wastewater treatment plant (WWTP). Afterwards gene regulation between up and downstream fish are compared. 

Our results have shown that mRNA levels are site dependent. Fish taken downstream generally express a different transcriptional regulation pattern than fish from upstream, indicating higher abundance of environmental stressors downstream. Furthermore, based on the gene expression analysis we were able to detect specific exposures with different environmental pollutants such as heavy metals, endocrine disruptors, pharmaceuticals or pesticides. Indeed, chemical analysis confirmed presence of such compounds in the water from the test sites. Therefore, it appears that our method is a promising screening assay for assessing surface water quality and fish health. The biomarker gene sets are very flexible and further adaptation for specific effects and other applications are possible.

Our team is also establishing a fish cell line assay as an in vitro water monitoring tool (link to animal alternatives), a real animal free approach. For this approach, permanent rainbow trout cell lines are directly exposed in the lab with surface water samples from the field sites. Then, the transcriptional regulation is measured in the cells and compared with the gene expression results from the wild caught fish and chemical analysis.