Metal concentrations in wetland plant tissues influences transfer to terrestrial food webs

Abstract

Wetland plants tolerate potentially hazardous metals through a variety of strategies, including exclusion or accumulation. Whether plants sequester metals and where they store them in their tissues is important for understanding the potential role of plants as remediators or vectors of metals to terrestrial food webs. Here we evaluate metal sequestration in Great Salt Lake wetlands for one invasive (Phragmites australis; phragmites) and three native plant species, i.e. threesquare bulrush (Schoenoplectus americanus), hardstem bulrush (Schoenoplectus acutus), alkali bulrush (Bolboschoenus maritimus), and their terrestrial invertebrates. We observed higher concentrations of arsenic and copper than other metals in plant tissues, although high lead concentrations were observed in phragmites. All plants acted as excluders of arsenic and selenium, retaining the bulk of the metal mass in belowground tissues. In contrast, lead, copper, and cadmium were transferred to above ground tissues of hardstem bulrush and phragmites. The aboveground translocation facilitated the movement of these metals into invertebrates, with the highest concentrations in most cases found in predators. Though our results highlight the potential for metal remediation via wetland plant growth and removal, care should be taken to ensure that remediation efforts do not lead to bioaccumulation.

Keywords: Bioaccumulation; Biomagnification; Food webs; Metals; Phragmites.