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

Abstract

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 I~g 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.Rooted and submerged vascular plants can take up substances from their environment by one of two routes: either from the water column, through submerged shoots, or from interstitial water of the sediment, through the roots. The relative importance of these two routes for nutrient or for metal uptake, respectively, is not clear, although it is accepted that both pathways may operate in the same plant (Denny 1980 Campbell et al. 1985Campbell et al. , 1988.A number of investigators have suggested that aquatic macrophytes can serve as useful monitors of the bioavailability of sediment-bound toxic metals (Aulio 1980;Campbell et al. 1985Campbell et al. , 1988Lyngby and Brix 1987).Furthermore, the ability of rooted macrophytes to accumulate metals from the sediment compartment suggests that aquatic plants can play a role in metal cycling in lakes (Mclntosh et al. 1978;Larsen and Schierup 1981) by transferring metals to herbivores, by releasing metals during decomposition Schierup and Larsen 1981), or by secreting metals into the water column (Kraus et al. 1986). The cycling will be more effective if metal accumulated in the roots can be transported to the shoots.Many field studies have demonstrated metal accumulation in aquatic plants and the relative importance of root vs shoot accumulation seems quite variable. But because most field studies have not considered the root and shoot uptake separately, uptake routes and possible transport of metal within plants remain unclear.In order to address the relative importance of root vs shoot uptake in a rooted aquatic plant, we designed a laboratory experiment to assess the relative importance of two routes of Hg transfer between the sediment and Eriocaulon septan...

Detection and Quantification of Unbound Phytochelatin 2 in Plant Extracts of Brassica napus Grown with Different Levels of Mercury

“…Pea (Pisum sativum) and spearmint (Mentha spicata) absorb Hg from solution, and roots accumulate much greater amounts of Hg than shoots (Beauford et al, 1977). Similar results have been found in Norway spruce (Picea abies; Godbold and Hü tterman, 1988), willow (Wang and Greger, 2003), and aquatic plants (Coquery and Welbourn, 1994).…”

“…Kumar et al (1995) tested many fast-growing Brassicas, including rape plants (Brassica napus), for their ability to tolerate and accumulate metals. Many studies have shown that plant roots accumulate Hg when they are exposed to Hg-contaminated soils (Lenka et al, 1992;Coquery and Welbourn, 1994;Bersenyi et al, 1999;Kalac and Svoboda, 2000). Laboratory studies have shown that plant roots absorb Hg from solution and that roots accumulate a much greater amount of Hg than do shoots (Cavallini et al, 1999).…”

Hg, Cu, Pb, Cd, and Zn Accumulation in Macrophytes Growing in Tropical Wetlands

“…Coelho et al (2009) reported that sea grasses accumulated considerable amounts of Hg in the aboveground biomass, with belowground/aboveground ratios reaching as high as 1.4, while rooted macrophytes accumulated less Hg in their aboveground biomass than macroalgae. In the work of Coquery and Welbourn (1994), there was no evidence for the transport of Hg from roots to shoots of the submerged isoetid macrophyte Eriocaulon septangulare With.…”

Effects of macrophytes on the fate of mercury in aquatic systems

“…Basipetal transport of IHg was also reported in Eriocaulon septangulare , but no measurement of MeHg was performed . Overall, the existing literature suggests that in shoots IHg is mainly accumulated from the water, whereas MeHg is accumulated from both water and sediments through roots to shoots translocation .…”