MERCURY UPTAKE FROM CONTAMINATED WATER AND SEDIMENT BY THE ROOTED ANDSUBMERGED AQUATIC MACROPHYTE ERIOCAULON-SEPTANGULARE

Laboratory experiments were designed to assess the relative importance of root vs shoot uptake of mercury by the submerged isoetid aquatic m acrophyte Eriocaulon septangulare. Roots of mature plants that had bee n cultured for 31 days in sediments contaminated with non-toxic (appro x. 1 mug g-1) concentrations of inorganic mercury had significantly hi gher concentrations and significantly greater mercury content than pla nts cultured in the same way but in sediments without added mercury. U nder the same experimental conditions, mercury content of leaves was r elated to the concentration of mercury in the water, being greater in the treatments which had higher total mercury in the water. The mercur y in water in the experiments originated from the sediment. There was no evidence for transport of mercury from root to shoot within the pla nt, although there was possibly some transport in the opposite directi on. The design of the experiment avoided making two compartments with a physical separation between the water (leaf)/sediment (root) interfa ce, but with this design it was not possible to determine with certain ty whether or not ''downward'' transport of mercury occurred within th e plant. The results with E. septangulare and mercury support the idea that aquatic macrophytes can be useful monitors of metals in sediment s.