Assessment of Lemna gibba L. (duckweed) as a potential ecological indicator for contaminated aquatic ecosystem by boron mine effluent

Abstract

Duckweeds, as a group, are important early warning indicators for the assessment of contaminated ecosystems due to their propensity to accumulate pollutants. In the present study, we investigated the potential use of Lemna gibba L (Lemnaceae) as an ecological indicator for boron (B) mine effluent containing B concentration above 10 mg l(-1). For this purpose, L gibba fronds were grown for 7 days in simulated water contaminated with B mine effluent. The important note is that this study was carried out in Kirka (Eskisehir, Turkey) B reserve area, which is the largest borax reserve in all over the world, under natural climatic conditions in the field. The results demonstrated that accumulations of B by L. gibba gradually increased based on the initial B concentrations (10, 25, 50,100, and 150 mg l(-1)) of the mine effluent. B concentration in the dry weight of the plant reached 639 mg kg(-1) when the minimum initial dosage (10 mg l(-1)) was applied and 2711 mg kg(-1) when the maximum initial dosage (150 mg l(-1)) was applied during the study. However, significant reductions in their relative growth rates occurred in 50, 100 and 150 mg l(-1) initial B concentrations. Results suggest that 25 mg l(-1) B concentration in water seemed to be a sensitive endpoint for L. gibba that could be used as a critical bioindicator level of B contaminated water. Following our data, we also constructed a simple growth model under the climatic conditions in this region of Turkey, but in instructive as a worldwide model. L gibba is, therefore, suggested to be able to use as both an indicator and a phytoremediation tool because of its high accumulation capacity for B contaminated water