Mercury movement from Hg-enriched wetland soils to arboreal food webs: a weak role for folivory

Abstract

Mercury (Hg) is a toxicant of concern, particularly in aquatic food webs. Mercury can move to terrestrial systems through consumption of aquatic prey or emergence of insects with aquatic larval phases. The possible movement of Hg from sediments to wetland plants and into terrestrial food webs though primary consumers has received less attention. We investigated differences and correlations in Hg in soil, wood and leaves of willows (Salix caroliniana) and folivorous beetles from a wetland with enhanced levels of Hg. Further, we compared samples from tree islands that had enriched Hg in soil through bird guano with control islands. Hg in any sample type did not correlate with Hg in any other sample type from the same island. We found higher [Hg] in soils and significantly higher [Hg] in leaves from colony islands, while [Hg] in beetles appeared to be higher in control islands. In any case, despite comparatively high [Hg] in soil and leaves, Hg in folivorous beetles was below detection levels and lower than that reported from other studies. We conclude that movement of Hg from wetland trees to terrestrial food webs through wetland vegetation is negligible in this ecosystem.