Assessing the responses and effects of marine pollution in highly developed coastal areas using biomarkers in a New Zealand triplefin, Forsterygion capito

Abstract

This thesis developed and validated methodologies using triplefin Forsterygion capito as bioindicators of environmental health to assess the impact of marine pollution. A series of molecular, histological, and physiological measurements were used to evaluate their health status in different sites in Auckland, New Zealand, testing the hypothesis that this species is a good indicator of pollution. In addition, a novel alternative to assessing pollution without harming the animals was developed. The research presented provides valuable information related to the health status of triplefin F. capito inhabiting both contaminated and reference sites around Auckland. First, mRNA biomarkers were developed in the laboratory by inducing the expression of four target genes: cyp1a (cytochrome P450), mt (metallothionein), vtg (vitellogenin), and cyp19b (cytochrome P450 aromatase) in the triplefin fish F. capito. Levels of cyp1a were upregulated in the livers of fish exposed to benzo(a)pyrene, and the vtg gene was a significant biomarker of oestradiol exposure in male fish. In the field study, the transcriptional responses of mt and cyp1a were shown to be strong molecular biomarkers showing high mRNA levels in fish from a contaminated site. In addition, vtg mRNA levels were elevated in a male fish from another contaminated site. To evaluate the general health of this species, biomarkers of effects at intermediate biological level were used. The Fulton's condition factor provided an initial indication of this species's health, and suggested that some condition factor values were associated with metal pollution via synergistic effect between chemicals. Lesions found in livers and gills were non-specific to certain stressors, but the high prevalence and intensity of telangiectasia and hyperplasia in gills seemed to be associated with metals. Finally, to test the hypothesis that the bacterial communities found in fish skin mucus reflect the quality of the surrounding water, a novel method was proposed as a non-invasive technique using next generation DNA sequencing technology. Our results showed clear differences in the bacterial communities from fish mucus collected between contaminated and reference sites. Bacteria in this thesis were also commonly found in other fish species, indicating that the methodology was successfully developed. The majority of the bacterial community in this study were associated with hydrocarbons rather than with metals. All in all, a comprehensive idea of the responses and effects of pollution through this fish species was obtained. Therefore, due to the habitual characteristics of this species and our findings, it is highly recommended that triplefin fish F. capito would be a good sentinel sp. for further monitoring programmes.