Mercury methylation, uptake and bioaccumulation by the earthworm Lumbricus terrestris ( Oligochaeta )

Álvarez, Carolina Rodríguez; Jiménez-Moreno, María; Bernardo, Francisco Javier Guzmán; Martín-Doimeadios, Rosa C. Rodríguez; Nevado, J. J. Berzas

doi:10.1016/j.apsoil.2014.06.008

Cited by 28 publications

(5 citation statements)

References 41 publications

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“…The U.S. Environmental Agency (2010) defined the Bioaccumulation factor as ‘The ration of the contaminant in an organism to the concentration in the ambient environment at a steady state, where the organism can take in the contaminant through ingestion with its food as well as through direct content’. It is calculated as the ratio of the Hg concentration in the earthworm (in µg/g dry wt) to the total soil Hg content (in µg/g dry wt) (Álvarez et al 2004 ; Rodríquez Álvarez et al 2014 ; Nannoni et al 2011 ). Previous studies (Burton et al 2006 ; Nannoni et al 2011 ) found BAF to be <1 which is in agreement with value obtained in the present study (Table 5 ).…”

Section: Resultsmentioning

confidence: 99%

Bioaccumulation of total mercury in the earthworm Eisenia andrei

2016

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Earthworms are a major part of the total biomass of soil fauna and play a vital role in soil maintenance. They process large amounts of plant and soil material and can accumulate many pollutants that may be present in the soil. Earthworms have been explored as bioaccumulators for many heavy metal species such as Pb, Cu and Zn but limited information is available for mercury uptake and bioaccumulation in earthworms and very few report on the factors that influence the kinetics of Hg uptake by earthworms. It is known however that the uptake of Hg is strongly influenced by the presence of organic matter, hence the influence of ligands are a major factor contributing to the kinetics of mercury uptake in biosystems. In this work we have focused on the uptake of mercury by earthworms (Eisenia andrei) in the presence of humic acid (HA) under varying physical conditions of pH and temperature, done to assess the role of humic acid in the bioaccumulation of mercury by earthworms from soils. The study was conducted over a 5-day uptake period and all earthworm samples were analysed by direct mercury analysis. Mercury distribution profiles as a function of time, bioaccumulation factors (BAFs), first order rate constants and body burden constants for mercury uptake under selected conditions of temperature, pH as well as via the dermal and gut route were evaluated in one comprehensive approach. The results showed that the uptake of Hg was influenced by pH, temperature and the presence of HA. Uptake of Hg2+ was improved at low pH and temperature when the earthworms in soil were in contact with a saturating aqueous phase. The total amount of Hg2+ uptake decreased from 75 to 48 % as a function of pH. For earthworms in dry soil, the uptake was strongly influenced by the presence of the ligand. Calculated BAF values ranged from 0.1 to 0.8. Mercury uptake typically followed first order kinetics with rate constants determined as 0.2 to 1 h−1.

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Section: Resultsmentioning

confidence: 99%

Bioaccumulation of total mercury in the earthworm Eisenia andrei

2016

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“…However, the mechanisms behind the bioaccumulation of MeHg and THg in earthworms are still elusive. Increased MeHg:THg in earthworms could originate from a more efficient accumulation of MeHg over THg due to higher lipo-solubility [14,15]. Other lines of evidence support the idea that the methylation is controlled by the earthworm intestinal microbiome [16].…”

Section: Introductionmentioning

confidence: 86%

Soil Hg Contamination Impact on Earthworms’ Gut Microbiome

et al. 2020

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Mercury (Hg) is one of the most toxic heavy metals and is known for its persistence in the environment and potential to accumulate along the food chain. In many terrestrial polluted sites, earthworms are in direct contact with Hg contamination by ingesting large quantities of soil. However, little is known about the impact of Hg soil pollution on earthworms’ gut microbiome. In this study, two incubation experiments involving earthworms in soils from a long-term Hg-polluted site were conducted to assess: (1) the effect of soil Hg contamination on the diversity and structure of microbial communities in earthworm, cast and soil samples; and (2) how the gut microbiome of different digestive track parts of the earthworm responds to soil Hg contamination. The large accumulation of total Hg and methyl-Hg within the earthworm tissues clearly impacted the bacterial and fungal gut community structures, drastically decreasing the relative abundance of the dominating gut bacterial class Mollicutes. Hg-tolerant taxa were found to be taxonomically widespread but consistent along the different parts of the earthworm digestive tract. This study revealed that although Hg might not directly affect the health of macro-organisms in the food-web such as earthworms, their metabolism and legacy in the soil might be impacted through changes in their gut microbiome.

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“…Unfortunately, very high Hg 0 concentration (2-6 g/L) were used in these experiments and the experimental design does not allow discarding the possibility of Hg methylation in the substrate and subsequent MeHg uptake by the organisms. Rodríguez-Álvarez et al (2014) worked with the earthworm Lumbricus terrestris exposed to natural non-contaminated and historically Hg-contaminated soils. Four independent experiments were carried out using both soils with and without freshly IHg spike.…”

Section: Earthwormsmentioning

confidence: 99%