Arsenic accumulation by aquatic macrophyte coontail (Ceratophyllum demersum L.) exposed to arsenite, and the effect of iron on the uptake of arsenite and arsenate

In this study, the aquatic macrophyte Ceratophyllum demersum L. (coontail or hornwort) was tested for its efficiency of arsenic (As) uptake under laboratory conditions. Our results revealed that the solution pH had a significant effect on As accumulation by C. demersum (p<0.001). The accumulation was highest at pH 5 and decreased as pH values increased. Plants that were exposed to various concentrations of arsenite (As(III)) for 24 and 48h, exhibited tolerance and toxic responses, respectively. As accumulation by C. demersum depended on the concentrations of As(III) and the duration of exposure (p<0.001). At 40μM after 24h, plants accumulated 227.5μg Asg ^-1 dw and showed no visible symptoms of toxicity. However, after 48h, As level reached 302.4μgg ^-1 dw and biomass production decreased significantly. Toxic effects were evident by plant necrosis and negative biomass production, leading to a decrease in the amount of accumulated As. Also, the addition of iron (Fe) into the nutrient solutions (0.18mM) had contrasting effects on the uptake of 2 As species - the uptake of As(III) was enhanced by the presence of Fe, but the uptake of arsenate (As(V)) was considerably inhibited.