Analysis of bile fluorescence profiles of feral Nile tilapia as biomarkers of exposure to polycyclic aromatic hydrocarbons: associations with the rainfall

Abstract

The present study was conducted to evaluate the potential use of bile fluorescence patterns of feral Nile tilapia (Oreochromis niloticus) as biomarkers of exposure to polycyclic aromatic hydrocarbon (PAH) contaminations in tropical waters. Bile fluorescence profiles of the fish inhabiting two water bodies with different levels of PAH pollution (Weras Ganga and Bathalagoda reservoir) were investigated at regular intervals over two years (September 2007 to July 2009) using fixed wavelength fluorescence and synchronous fluorescence spectrometry. Despite temporal variability of the bile fluorescence patterns, the fluorescence signals corresponding to naphthalene-, phenanthrene-, pyrene- and benzo(a)pyrene- type metabolites were consistently higher in the fish from Weras Ganga compared to the fish from Bathalagoda reservoir and the laboratory maintained control fish indicating that the fish inhabiting Weras Ganga had been continuously exposed to higher levels of PAHs. Summated fluorescence for the four types of PAH metabolites and fluorescence signals corresponding to naphthalene- and pyrene- type metabolites in the fish from Weras Ganga were positively correlated (P < 0.05) with the rainfall pattern indicating more PAH inputs associated with the rainfall. Despite slight temporal variations, no significant associations were found between the biliary fluorescence signals in the fish from Bathalagoda reservoir and the rainfall pattern. This field study supports the use of bile fluorescence patterns in feral Nile tilapia as a simple and rapid method for screening contamination and bioavailability of PAH in tropical freshwater bodies.