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 10mgl−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 Kırka (Eskişehir, 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 150mgl−1) of the mine effluent. B concentration in the dry weight of the plant reached 639mgkg−1 when the minimum initial dosage (10mgl−1) was applied and 2711mgkg−1 when the maximum initial dosage (150mgl−1) was applied during the study. However, significant reductions in their relative growth rates occurred in 50, 100 and 150mgl−1 initial B concentrations. Results suggest that 25mgl−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.