Determining the Impacts of Environmental Contaminants to Zebra Mussels Using Genetic Biomarkers

Abstract

ABSTRACT DETERMINING THE IMPACTS OF ENVIRONMENTAL CONTAMINANTS TO ZEBRA MUSSELS USING GENETIC BIOMARKERS by Nicklaus James Neureuther The University of Wisconsin-Milwaukee, 2016 Under the Supervision of Professor Rebecca Klaper, PhD Persistent legacy contaminants and emerging chemicals of concern continue to be a threat to the function and health in the Great Lakes Areas of Concern (AOCs). While chemical monitoring programs traditionally sample water and sediment, these studies can only provide information of the type and level of contamination within an (AOC). This being said, information on the biological impacts to the biota are needed to measure impairments of chemical exposure, to support remediation efforts in their ability to eventually restore AOCs. To accomplish this, I proposed to measure chemical exposure using molecular biomarkers from D. polymorpha (Pallas, 1771), more commonly known as the zebra mussel. This species has been successfully used as a bioindicator of contamination in the Great Lakes and in Europe due to it being an invasive species and having the physiological qualities of being a sessile filter feeder. These unique physiological properties, in addition to the zebra mussel already having a library of gene expression biomarkers known to be critical in relation to stress and detoxification, including the genes: GST, AHR, P-gP and HSP70, made this organism an obvious choice. Working in conjunction with the already iii established chemical monitoring program, the NCCOS NOAA Mussel Watch Program (MWP), the goal was to test these genomic biomarkers to see how robust they could be as an indicator of exposure in conjunction with chemical data from the field. We demonstrated that in an aquatic environment that these genes of exposure revealed a significant relationship with the legacy contaminants polychlorinated bi-phenols (PCBs) and polycyclic aromatic hydrocarbons (PAHs) and the emerging contaminants, 4 nonylphenol (4NP) and triclocarban (TCC) over a gradient of contamination and that these results were affected by length of exposure. Likewise, AOCs are dynamic environments containing complex mixtures of contaminants, which tend to co-correlate, making it difficult to parse out effects of exposure from single contaminants. To investigate individual chemical and gene expression relationships further, zebra mussels were exposed to environmentally relevant levels of TCC under laboratory conditions. This study confirmed my field results that the gene GST could be a potential biomarker of TCC. As a whole, these two studies demonstrated that using the zebra mussel as not only a bioindicator of contamination but as a biomonitor of exposure using gene expression biomarkers could be an effective tool used by monitoring programs to help gauge restoration success.