Total mercury and methylmercury concentrations in water hyacinth (Eichhornia crassipes) from a South Carolina coastal plain river

Abstract

The Waccamaw River is located along the eastern coastline of South Carolina. Large areas of the shoreline contain water hyacinth (Eichhornia crassipes) mats. These plants trap organic matter, inhibit light and oxygen penetration into the water and serve as a substrate for bacterial colonization, which may be conducive to the formation of methylmercury. The purpose of this study was to quantify the amount of total and methylmercury in plants, water under the mats and surface water from an area adjacent to the mats. Concentrations of total and methylmercury and percentages of methylmercury in water samples ranged from 2.9 to 8.9 ng L−1, 0.2–2.5 ng L−1, and 9–31 %, respectively and were not significantly different between sites. Concentrations of total mercury in water hyacinth shoots and roots ranged from 2.2 to 58.7 ng g−1 dw and 29.7–71.9 ng g−1 dw, respectively. Methylmercury ranged from 0.84 to 2.24 ng g−1 dw (shoots) and from 8.95 to 37.1 ng g−1 dw (roots). Concentrations of total and methylmercury in the roots were significantly higher than the shoots. Percentages of methylmercury in the roots and shoots varied from 2 % to 63 % and were not significantly different. Total and methylmercury in one square meter of water hyacinth ranged from 8833–52,459 ng m−2 dw and from 2686–15,786 ng m−2 dw, respectively. These plants may represent another vector of methylmercury to aquatic food webs and contribute to the bioaccumulation of methylmercury in aquatic organisms.