engleski

Thallium bioaccumulation in different bioindicator organisms from the karst Krka River in Croatia

Metals present one of the major threats for aquatic systems due to their persistence, toxicity and potential to bioaccumulate in organisms. Naturally present trace metal concentrations in karst rivers are low which makes them very sensitive to anthropogenic influence. Krka River is a typical karst river in the Republic of Croatia whose lower part was proclaimed National Park. However, it is nowadays threatened by municipal and industrial wastewaters near the park border. The aim of this study was to evaluate Tl bioaccumulation in acanthocephalans, fish intestinal parasites known by their effective metal accumulation, and in species involved in their life cycle, fish and crustaceans, from two sampling locations (river source as a reference, and downstream of wastewater inputs as a polluted site) in autumn and spring. Thallium is a rare heavy metal but its high toxicity, water solubility and tendency of bioaccumulation made it a US EPA priority pollutant. It is released from both natural and anthropogenic sources. While generally present in the environment at low levels ; human impact has greatly increased its content [1]. HR ICP-MS was used to measure Tl concentrations in samples of digested acanthocephalans, gammarids and intestinal and muscle tissue of brown trouts, as well as in water samples. In both seasons, Tl concentrations were comparable in crustaceans and fish intestine, but these levels were 2-4 times higher than in muscle, although all followed the same pattern with 2-3 times higher levels in the reference compared to the polluted site. The same pattern was observed in acanthocephalans, but Tl levels were around 30 times higher than in gammarids and fish intestine and around 100 times higher than in fish muscle, therefore confirming effective Tl accumulation. Such results are not in accordance with Tl concentrations in river water, which were very low and comparable between sites (4-5 ng L-1) [2]. Thus, obvious higher Tl exposure at the reference site needs strict monitoring and further investigation of potential Tl sources, dietborne exposure and sediment content.

thallium ; bioindicator ; brown trout ; acanthocephalans ; bioaccumulation

nije evidentirano