The present study was carried out to assess the levels of eight metals viz. Pb, Cu, Cd, Ni, Cr, Mn, Hg and Zn in two species of food fish, Etroplus suratensis and Ambassis commersoni from Negombo estuary. The levels of Hg were analyzed by cold vapour atomic absorption spectrometry whereas the other metals were analyzed by flame/graphite furnace atomic absorption spectrometry. Total metal levels in muscle, gill and liver tissues of the fish showed a wide range. Accumulation of most metals in the tissues of the fish followed the increasing order, muscle < gills ≤ liver. Of the different metal levels detected in the fish, only the level of Cd in liver tissue of 6% of E. suratensis and 12% of A. commersoni exceeded the level specified for human consumption by European Union. Interspecies comparisons revealed that mean level of Zn in the muscle tissue of A. commersoni was two fold higher than that of E. suratensis. The levels of metals in the muscle tissue of both fish species were positively correlated with the body weight or body length of the fish. Based on the levels of Hg, Pb, and Cd in the fish, edible muscle of both fish species collected from the estuary was found to be safe for human consumption. However, heavy consumption of bigger size fish may pose a health risk to the consumers as there were strong positive correlations between body weight or body length and metal levels in muscle tissues of both species of fish. H.A.P. Indrajith et al./ Sri Lanka J. Aquat. Sci. 13 (2008): 63-81

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...

The brackish coastal wetlands in the Bundala National Park, the only RAMSAR site of southern Sri Lanka, are an important waterfowl habitat and economic zone. Bundala Lagoon, one of the three key lagoons of the Bundala wetlands, remains largely intact and relatively pristine, but the other two interconnected lagoons, namely, Embilikala and Malala, are impacted by drainage from 25.6 km 2 of upstream agricultural lands. Seasonal variations of water quality of the three lagoons and the key processes affecting water quality and quantity in these lagoons were studied during three agricultural seasons, to better understand the characteristics of the system. Bundala Lagoon, which was not affected by agriculture, recorded the highest ammonia and total nitrogen concentrations and the lowest phosphorus levels. Higher phosphorus levels in Embilikala Lagoon were related to the upstream agricultural activities with 65% of its total phosphorus measured being reactive phosphorous. Phosphorus additions occurred during the early months of the paddy cultivating seasons. Processes affecting the water quality of the Embilikala-Malala lagoon system included agricultural drainage, livestock additions, and breaching of the sand bar between Malala Lagoon and the sea. The salinity level of the Bundala Lagoon was higher than the others due to the connection to the sea, salt farms in the western part, and less dilution of salt from relatively low surface runoff and rainwater. All three lagoons reported pH levels conducive to most aquatic species. The primary production by phytoplankton in the lagoons of the Bundala wetland was phosphorus limited regarding their ratios of nitrogen to phosphorus. This study provides an overview of the present status of the lagoons of the wetland. Further work is needed to evaluate the impact of the external nutrient and water inputs on the flora and fauna of the lagoon environments. Suitable management practices to ensure the sustainability of the lagoon ecosystem can be derived through this increased understanding.

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.

Bioaccumulation potential of selected heavy metals viz. Pb, Cd, Cr, Cu, and Zn in muscle, gills and liver of food fish, Mystus gulio (Anguluwa) inhabiting in Bolgoda Lake were assessed by analyzing metal levels in the fish collected from four main locations: Weras Ganga, North Lake, Bolgoda Ganga and South Lake. In addition, water and sediment samples were taken concurrently from the sampling locations for determination of the metal levels. The metal levels were analysed by atomic absorption spectrometry using standard procedures. Dissolved total metal levels in lake water (in µg L-1) varied depending on the sampling location: