Efficiency of metal bioaccumulation in acanthocephalans, gammarids and fish in relation to metal exposure conditions in a karst freshwater ecosystem.

ABSTRACT

BACKGROUND: Each of the bioindicator organisms studied, such as fish, crustaceans, or parasites, have certain advantages when used in the assessment of metal exposure. In this research, special attention was given to intestinal parasites, acanthocephalans, as effective metal bioaccumulators with the main aim of estimating and comparing metal accumulation in all organisms involved in their life cycle and testing their usage as sensitive bioindicators in metal exposure assessments. METHODS: Efficiency of metal accumulation was evaluated in fish intestine (brown trout, Salmo trutta Linnaeus, 1758), gammarids (Gammarus balcanicus Schäferna, 1922) and acanthocephalans (Dentitruncus truttae Sinzar, 1955) in the Krka River at site threatened by industrial and municipal wastewaters (Town of Knin) and reference site (Krka River source) in two seasons (autumn and spring). All samples were digested in a drying oven at 85 °C for 3.5 h using nitric acid and hydrogen peroxide. Samples were diluted with ultrapure water and total concentrations of 15 trace and macroelements were measured by HR ICP-MS. RESULTS: Higher concentrations of Co, Cu, Fe and Mn at the contaminated than at the reference site were recorded in all bioindicator organisms. Additionally, Se, Sr, Zn, Ca, K and Mg were elevated at the contaminated site in acanthocephalans, Cs, Pb, Zn and K in gammarids and Se, Sr and Ca in fish intestine. Opposite, concentrations of Cd, Cs and Rb were mostly higher in organisms from the reference than wastewater impacted site, which did not coincide with waterborne metal exposure but indicated importance of assessing dietary metal uptake. CONCLUSION: More effective metal accumulation was confirmed in acanthocephalans than fish and gammarids, especially of Cd and Pb in respect to gammarids, and of Cd, Cu, Pb, Mn and Sr in respect to fish intestine. Thus, both fish intestine and whole body of D. truttae were confirmed as sensitive indicators of low environmental metal exposure, reflecting site-specific differences, which proved their potential to be used in monitoring programmes and metal exposure assessment in real environmental situations.