Assessment of bile fluorescence patterns in a tropical fish, Nile tilapia (Oreochromis niloticus) exposed to naphthalene, phenanthrene, pyrene and chrysene using fixed wavelength fluorescence and synchronous fluorescence spectrometry.

Bile fluorescence patterns in Nile tilapia, a potential fish for biomonitoring tropical water pollution were assessed following exposure to selected polycyclic aromatic hydrocarbons (PAHs): naphthalene, phenanthrene, pyrene and chrysene. Non-normalized fixed wavelength fluorescence signals in the fish exposed to these PAHs reflected dose and/or time response relationships of their metabolism. Normalizing signals to biliverdin introduced deviations to these response patterns. The optimal wavelength pairs (excitation/emission) for synchronous fluorescence scanning measurements of bile metabolites of naphthalene, phenanthrene, pyrene and chrysene were identified as 284/326, 252/357, 340/382 and 273/382 respectively. This study supports the use of bile fluorescence in Nile tilapia by fixed wavelength fluorescence and synchronous fluorescence spectrometry with non-normalized data as a simple method for screening bioavailability of these PAHs.

Assessment of biological effects of pollutants in a hyper eutrophic tropical water body, Lake Beira, Sri Lanka using multiple biomarker responses of resident fish, Nile tilapia (Oreochromis niloticus).

Biomarkers measured at the molecular and cellular level in fish have been proposed as sensitive "early warning" tools for biological effect measurements in environmental quality assessments. Lake Beira is a hypertrophic urban water body with a complex mixture of pollutants including polycyclic aromatic hydrocarbons (PAHs) and Microcystins. In this study, a suite of biomarker responses viz. biliary fluorescent aromatic compounds (FACs), hepatic ethoxyresorufin O-deethylase (EROD) and glutathione S-transferase (GST), brain and muscle cholinesterases (ChE), serum sorbitol dehydrogenase (SDH), and liver histology of Oreochromis niloticus, the dominant fish inhabiting this tropical Lake were evaluated to assess the pollution exposure and biological effects. Some fish sampled in the dry periods demonstrated prominent structural abnormalities in the liver and concomitant increase in serum SDH and reduction in hepatic GST activities in comparison to the control fish and the fish sampled in the rainy periods. The resident fish with apparently normal liver demonstrated induction of hepatic EROD and GST activities and increase in biliary FACs irrespective of the sampling period indicating bioavailability of PAHs. Muscle ChE activities of the resident fish were depressed significantly indicating exposure to anticholinesterase substances. The results revealed that fish populations residing in this Lake is under threat due to the pollution stress. Hepatic abnormalities in the fish may be mainly associated with the pollution stress due to recurrent exposure to PAHs and toxigenic Microcystis blooms in the Lake.

Use of biomarkers in Nile tilapia (Oreochromis niloticus) to assess the impacts of pollution in Bolgoda Lake, an urban water body in Sri Lanka.

The present study reports the first analysis of water pollutants in Sri Lankan waters using a suite of biomarkers in Nile tilapia (Oreochromis niloticus) residing in Bolgoda Lake which receives urban, industrial and domestic wastes from multiple sources. The fish were collected from the lake in the dry period (April 2005) and wet periods (September 2005, October 2006) and the levels of biomarkers viz. hepatic ethoxyresorufin O-deethylase (EROD), glutathione S-transferase (GST), metallothioneins, biliary fluorescent aromatic compounds, brain and muscle cholinesterases (ChE) were compared with those of the laboratory reared control fish and the fish obtained from a less polluted water body, Bathalagoda reservoir (reference site). The results revealed that biomarker levels of the fish collected from the reference site were not significantly different from the controls. Hepatic EROD and GST activities in fish from Bolgoda Lake were induced 4.2-16.6 folds and 1.4-3.3 folds respectively compared with the control fish. Analysis of bile in the lake fish revealed recent uptake of naphthalene, pyrene and benzo(a)pyrene type polycyclic aromatic hydrocarbons (PAHs). The induction of EROD activities in feral fish reflects the exposure of fish to aryl hydrocarbon receptor agonists including PAHs present as pollutants in the Bolgoda Lake. Cholinesterase activity in the fish inhabiting one sampling site of Bolgoda Lake was lower (22-40% inhibition) than the activity measured in the control fish indicating the presence of anticholinesterase pollutants in the area. Hepatic metallothionein levels in the lake fish were higher (1.9-3.2 folds) in comparison to the controls indicating metal exposure. The results support the potential use of these biomarkers in Nile tilapia in assessing pollution in tropical water bodies.

Occurrence and distribution of polycyclic aromatic hydrocarbons (PAHs) in Bolgoda and Beira Lakes, Sri Lanka.

The pollution of polycyclic aromatic hydrocarbons (PAHs) has been widely used to assess the potential impact of anthropogenic activities on aquatic environments because their occurrence in water is closely tied to urban activities. Many PAHs possess mutagenic and carcinogenic properties (Menzie et al. 1992). PAH distribution and toxic potentials have therefore been the focus of numerous studies in waterways including the Great Lakes (USEPA Report 1994), Yanisei Bay (Dahle et al., 2003), and the Fraser River basin (Yunker et al., 2002). Sri Lanka, a small island nation with a dense population of about 20 million people, faces a multitude of environmental stresses ranging from deforestation to traffic congestion and the deterioration of water quality. This study was undertaken to understand the occurrence, sources, and potential impacts of PAHs in the waterways of Sri Lanka. Two lakes, Beira and Bolgoda, were selected for the study due to their economic value and high level of pollution. Beira Lake, situated in downtown Colombo, the capital city of Sri Lanka, is highly polluted. Sources of pollution are multifarious. For instance, clusters of communities have sprung up along the edges of the lake in recent times and many shacks have been built. These communities are generally not connected to municipal sewer systems and substantial quantities of domestic sewage and untreated wastewaters are discharged directly into the lake. Small industries have also grown rapidly around the lakes, most of which are not believed to have adequate facilities to treat industrial wastewater, especially organic wastes. In addition, Sri Lanka has experienced an upsurge of motor vehicles, including millions of three-wheelers and minivans that are powered by leaded gasoline and diesel fuels. Traffic congestion and severe air pollution due to vehicle emissions are now common daily occurrences and are considered a major potential source of PAHs in the lakes. Although Bolgoda Lake is situated some distance from Colombo, it is heavily polluted due to the growing number of towns with an attendant increase in small businesses and various industries along its shores. These new developments have undoubtedly impacted the lake through the discharge of PAHs and other anthropogenic chemicals present in industrial wastewater and from street runoffs. The lake, additionally, receives a large quantity of pollutants from the industrial zone in the north. The pollution caused by PAHs has led to various studies on the distribution and origin of PAHs in the environment (Yunker et al., 1996; Budzinski et al., 1997). Based on the proportions of different PAHs, most studies aim to distinguish PAHs of petrogenic sources from those of pyrolytic origins. The PAHs of petrogenic origin, prevalent in coals and fossil fuels, are formed from diagenesis of sedimentary organic material under low to moderate temperature and tend to consist of low-molecular-weight PAHs with two to three aromatic rings (Potter et al., 1998). The pyrolytic PAHs, on the other hand, are formed at much higher temperatures (greater than 500 degrees C for example) and consist mainly of four or more aromatic rings (Commins, 1969). Thus, an increase in the proportion of higher-molecular-weight PAHs is taken to be indicative of contaminations of mainly pyrolytic origin. The prevalence of high-molecular-weight PAHs in the urban dusts (Wise et al., 1988) and in atmospheric particles (Sicre et al., 1987) illustrates the chemistry of their formation at high temperature. The purpose of this study was to determine the PAH concentrations and distribution with respect to sampling location, origin and sources in two polluted lakes.