Phytoremediation of anatoxin-a by aquatic macrophyte Lemna trisulca L.

Abstract

The neurotoxin anatoxin-a (ANTX-a), one of the most common cyanotoxin, poses a health risk to people and can be lethal to aquatic organisms. This paper presents results on its bioremediation by the aquatic macrophyte Lemna trisulca. We show that the plant is resistant to the harmful impact of toxin and is capable of removing ANTX-a from water. Some of the ANTX-a concentrations which were used in our experiments were much higher than those found in natural conditions. The exposition of L. trisulca to 2.5μg ANTX-a/mL did not affect its biomass accumulation within 24d. Significant decreases in biomass content by 21% and 30% were demonstrated in samples cultivated in media containing 12.5μg ANTX-a/mL after 18 and 24day of experiment, respectively. One gram of fresh weight (f.w.) of L. trisulca cultured for 14d in the media containing 50μg ANTX-a removed 95% of the initial toxin concentration; for media with 250μg ANTX-a, 86% was removed. In tests of ANTX-a binding stability and degradation we transferred the macrophyte to fresh media without added toxin; within 14d the content of accumulated ANTX-a in the macrophyte decreased by 76% (from initial 19.3μg ANTX-a/gf.w.), 71% (from 37.3μg ANTX-a/g f.w.) and 47% (from 63.7μg ANTX-a/g f.w.). The quantity of ANTX-a released to media was minimal: from 3.5% to 5.1% of the initial bioaccumulated value. The data show that part of the ANTX-a was degraded. Mass spectra analyses did not indicate transformation of ANTX-a to already known forms. These findings suggest that L. trisulca has much potential as a phytoremediation agent for stabilization of aquatic environments.