Metabolomics Provide Sensitive Insights into the Impacts of Low Level Environmental Contamination on Fish Health-A Pilot Study

Abstract

This exploratory study aims to investigate the health of sand flathead (Platycephalus bassensis) sampled from five sites in Port Phillip Bay, Australia using gas chromatography-mass spectrometry (GC-MS) metabolomics approaches. Three of the sites were the recipients of industrial, agricultural, and urban run-off and were considered urban sites, while the remaining two sites were remote from contaminant inputs, and hence classed as rural sites. Morphological parameters as well as polar and free fatty acid metabolites were used to investigate inter-site differences in fish health. Significant differences in liver somatic index (LSI) and metabolite abundance were observed between the urban and rural sites. Differences included higher LSI, an increased abundance of amino acids and energy metabolites, and reduced abundance of free fatty acids at the urban sites compared to the rural sites. These differences might be related to the additional energy requirements needed to cope with low-level contaminant exposure through energy demanding processes such as detoxification and antioxidant responses as well as differences in diet between the sites. In this study, we demonstrate that metabolomics approaches can offer a greater level of sensitivity compared to traditional parameters such as physiological parameters or biochemical markers of fish health, most of which showed no or little inter-site differences in the present study. Moreover, the metabolite responses are more informative than traditional biomarkers in terms of biological significance as disturbances in specific metabolic pathways can be identified.

Keywords: Platycephalus bassensis; amino acids; biomarkers; diet; energy metabolism; fatty acid metabolites; flathead; metals.

Figure 1

Map showing the location of sampling sites where sand flathead (Platycephalus bassensis) were collected in Port Phillip Bay, Victoria, Australia in March 2015. Land use in the surrounding areas and proximity to the cities of Melbourne and Geelong are also included.

Figure 2

Partial least squares discriminant analysis (PLS-DA) showing the separation of polar metabolites in the livers of female sand flathead (Platycephalus bassensis) collected at five sites in Port Phillip Bay, Victoria, Australia in March 2015. Cross validation results are in the Supplementary Materials as Figure S1 and Table S1.

Figure 3

Box plots showing the abundance of different classes of polar metabolites in the livers of female sand flathead collected from five sites (n = 3–6 fish per site) around Port Phillip Bay, Victoria, Australia in March 2015. Green = Sorrento, blue = St Leonards, yellow = Corio Bay, purple = Mordialloc, and red = Hobsons Bay. Blue outline represents the rural sites, red outline represents the urban sites.

Figure 4

Partial least squares discriminant analysis (PLS-DA) showing the separation of free fatty acid metabolites in the livers of female sand flathead collected at five sites in Port Phillip Bay, Victoria, Australia in March 2015. Cross validation results are in the Supplementary Materials as Figure S3 and Table S4.

Figure 5

Box plots showing the abundance of some free fatty acid metabolites in the livers of female sand flathead collected from five sites (n = 3–6 fish per site) in Port Phillip Bay, Victoria, Australia in March 2015. Green = Sorrento, blue = St Leonards, yellow = Corio Bay, purple = Mordialloc, and red = Hobsons Bay. Blue outline represents rural sites; red outline represents urban sites.