Mercury uptake from contaminated water and sediment by the rooted and submerged aquatic macrophyte Eriocaulon septangulare

Abstract

Laboratory experiments were designed to assess the relative importance of root vs shoot uptake of mercury by the submerged isoetid aquatic macrophyte Eriocaulon septangulare. Roots of mature plants that had been cultured for 31 days in sediments contaminated with non-toxic (approx. 1 μg g−1) concentrations of inorganic mercury had significantly higher concentrations and significantly greater mercury content than plants cultured in the same way but in sediments without added mercury. Under the same experimental conditions, mercury content of leaves was related to the concentration of mercury in the water, being greater in the treatments which had higher total mercury in the water. The mercury in water in the experiments originated from the sediment. There was no evidence for transport of mercury from root to shoot within the plant, although there was possibly some transport in the opposite direction. The design of the experiment avoided making two compartments with a physical separation between the water (leaf)/sediment (root) interface, but with this design it was not possible to determine with certainty whether or not “downward” transport of mercury occurred within the plant. The results with E. septangulare and mercury support the idea that aquatic macrophytes can be useful monitors of metals in sediments.