Insect Life Traits Are Key Factors in Mercury Accumulation and Transfer within the Terrestrial Food Web

Abstract

16As plants and associated insects are at the bottom of some terrestrial food webs, they are the 17 primary contributors to mercury (Hg) fluxes in ecosystems. In addition to the trophic position 18 of these organisms, factors related to their life traits have been hypothesized to influence their 19 exposure to Hg. This study investigates the transfer of Hg in a soil-nettle-insect system and 20 the insect-related factors affecting their Hg concentrations in a revegetated chlor-alkali 21 landfill. Twenty-three insect species were identified and classified according to their life 22 traits, their relationship with nettle and their morphological characteristics. We observed low 23 total mercury (THg) concentrations in nettles, with only 1% methylmercury (MeHg) being 24 detected, while concentrations ranged from 5 to 3700 µg/kg dry wt. in insects with a MeHg 25 percentage of up to 75%. The nettle-related insects were primarily exposed to Hg through the 26 food web with significant biomagnification, particularly at the level of secondary predators. 27 Within the nettle-unrelated group, the insect habitat was the most explanatory factor, with the 28 highest enrichment being for the insects that spent part of their cycle in direct contact with Hg 29 sources. Therefore, these insects require special attention because they are an essential vector 30 of Hg transfer for terrestrial top predators. 34Landfills in the chlor-alkali industries require stabilization of mercury (Hg) to prevent 35 air pollution by evaporated Hg 1 . Revegetation of these sites offers a suitable solution to 36 confine the Hg released from the soil in plant biomass 2 , as plants are net sinks that incorporate 37 the atmospheric Hg into leaf tissues 3 . These plantations, mainly from Salicaceous species (i.e., 38 willow), favour the appearance of spontaneous herbaceous cover highly dominated by the 39 common stinging nettle, Urtica dioïca L. (Urticaceae) 4 . In natural conditions, this nettle is 40 considered an invertebrate "super-host" providing food for a large diversity of insects with 41 different biology 5 and is involved in strong trophic interactions [6][7][8] . In this context, herbivorous 42 insects on revegetated landfills are potentially exposed to Hg and, more precisely, to 43 methylmercury (MeHg), the form of Hg that biomagnifies readily from soil and sediment to 44 plants 9 . The accumulation of MeHg in herbivorous insects can cause serious physiological, 45 neurological, behavioural and reproductive disorders for insects or invertebrate predators, 46 birds and mammals through their diet 10,11 . 47Studies and reviews focusing on Hg transfer in the terrestrial food chain and its 48 toxicity on specific groups (i.e., birds, invertebrates, mammals, and microorganisms) have 49 increased since 2010 12,13 . Some recent works, mainly targeting high trophic levels taxa, 50 concluded that elevated MeHg concentrations in high trophic wildlife are ubiquitous across 51 the world's ecosystems and that there is a lack of accurate information on...

Distributions of Total Mercury and Methylmercury in Dragonflies from a Large, Abandoned Mercury Mining Region in China

“…Similar trends were also observed at sites AZR (THg: r 2 = 0.15, P = 0.000; MeHg: r 2 = 0.14, P = 0.002) and XXR (THg: r 2 = 0.30, P = 0.003; MeHg: r 2 = 0.20, P = 0.000; Figures 3a, b). The result is consistent with a previous report of a positive relationship (THg: r 2 = 0.38, P ≤ 0.001) between bodyweight and THg concentration in predatory insects such as Nabidae (Yung et al, 2019). δ 15 N Species O. triangulare and P. avescens from site WK exhibited signi cant differences in THg (P < 0.001) and MeHg (P < 0.001).…”

“…Life traits such as feeding guilds, life cycle, and habitat are the main factors controlling the accumulation of Hg (Yung et al, 2019). In the present study, signi cant bioaccumulation was apparent in the dragon ies, in which Hg concentrations increased with bodyweight.…”

Partial overlap of fungal communities associated with nettle and poplar roots when co-occurring at a trace metal contaminated site

“…A detailed description of the experimental design is provided in Ciadamidaro et al, (2017) and Phanthavongsa et al, (2017). Five years after planting, the spontaneous herbaceous layer evolved in the same way as that of another similar experiment set up in eastern France, with a dominance of the stinging nettle under poplars with a coverage rate depending on the poplar cultivar (Yung et al, 2019). In order to get rid of this variable and appreciate the contaminant effect on the microbiomes associated with nettle and poplar roots, we selected only one plot for each poplar cultivar (i.e.…”

“…The stinging nettle (Urtica dioica L.) colonizes a vast diversity of nitrophilic environments and particularly anthropogenic areas (Balabanova et al, 2015;Shams et al, 2010;Viktorova et al, 2016). It has thus been frequently observed as a companion species in a wide range of nitrogen-rich environments such as Salicaceous plantations at both natural (Cronk et al, 2016) and anthropized sites (Yung et al, 2019). Nettle has recently raised growing interest in the domain of phytomanagement because it (i) constitutes a new resource of high-quality herbaceous fibres for the manufacture of biomaterials (Bacci et al, 2009;Di Virgilio et al, 2015;Jeannin et al, 2019Jeannin et al, , 2020, (ii) promotes the biodiversity of local entomofauna (James et al, 2015;Perrin, 1975;Yung et al, 2019) and (iii) spontaneously grows in contaminated sites (Murtic et al, 2019;Paukszto and Mirosławski, 2019;Viktorova et al, 2016).…”

Native stinging nettle (Urtica dioica L.) growing spontaneously under short rotation coppice for phytomanagement of trace element contaminated soils: Fibre yield, processability and quality

“…The control site in France is a natural area located at Courcelle les Montbéliard, 140 km east of the site S1, not directly influenced by the point source. (Yung et al, 2019b) gives a description of this site. The other control site is located in Belgium at Ghent region at 120 km north east of the site S2.…”