posted on 2019-02-07, 00:00authored byMartin Tsz-Ki Tsui, Songnian Liu, Rebecka L. Brasso, Joel D. Blum, Sae Yun Kwon, Yener Ulus, Yabing H. Nollet, Steven J. Balogh, Sue L. Eggert, Jacques C. Finlay
Compared to the extensive
research on aquatic ecosystems, very
little is known about the sources and trophic transfer of methylmercury
(MeHg) in terrestrial ecosystems. In this study, we examine energy
flow and trophic structure using stable carbon (δ13C) and nitrogen (δ15N) isotope ratios, respectively,
and MeHg levels in basal resources and terrestrial invertebrates from
four temperate forest ecosystems. We show that MeHg levels in biota
increased significantly (p < 0.01) with δ13C and δ15N at all sites, implying the importance
of both microbially processed diets (with increased δ13C) and trophic level (with increased δ15N) at which
organisms feed, on MeHg levels in forest floor biota. The trophic
magnification slopes of MeHg (defined as the slope of log10MeHg vs δ15N) for these forest floor food webs (0.20–0.28)
were not significantly different (p > 0.05) from
those observed for diverse temperate freshwater systems (0.24 ±
0.07; n = 78), demonstrating for the first time the
nearly equivalent efficiencies with which MeHg moves up the food chain
in these contrasting ecosystem types. Our results suggest that in
situ production of MeHg within the forest floor and efficient biomagnification
both elevate MeHg levels in carnivorous invertebrates in temperate
forests, which can contribute to significant bioaccumulation of this
neurotoxin in terrestrial apex predators.