Mercury methylation and associated microbial communities in vegetated and unvegetated mudflat of the Ganghwa intertidal wetland, Yellow Sea
Abstract
Methylmercury (MeHg) that acts as a neurotoxin is susceptible to biomagnification, which ultimately affect human health. Hg-methylation mostly occurs through biological processes. Currently, several studies on hgcAB gene required for Hg-methylation have reported various Hg-methylating communities, including syntrophs, methanogens, and Firmicutes. Intertidal sediments in coastal ecosystems are regarded as a biogeochemical hot spot where rapid turnover of organic material and inorganic nutrients occurs in the land-sea continuum. In this regards, the Ganghwa intertidal wetland (GIW) developed in the mid-west of the Korean peninsula is considered as a significant environmental buffer mineralizing organic matter and pollutants loaded via inflow of the Han River passing through the Seoul-Gyeonggi-Incheon metropolitan area where a population over 25 million people reside. However, little is known on the mercury methylation and directly associated microbial communities in the GIW. We investigated vertical distribution of total mercury (THg) and MeHg and microbial communities related to Hg-methylation in vegetated mudflat (VMF) and unvegetated mudflat (UMF) in GIW where microbial sulfate reduction (SR) is is a significant organic carbon oxidation pathway. The concentrations of THg and MeHg were higher in surface sediments of the VMF site (42.5 and 0.3 ng g-1 in dry weight, respectively) than in the UMF site (33.2 and 0.08 ng g-1, respectively), which indicate that the presence of vegetation influences on distribution of THg and MeHg. Mercury methylation rate (MMR) showed significant positive correlation with SRR (r2 = 0.7406, p = 0.0392), which indicated that mercury methylation is closely related to sulfate reduction. Phylogenic analysis of hgcA gene revealed that bacteria closely related to Deltaproteobacteria and Chloroflexi were the two major bacterial groups responsible for the Hg-methylation. Especially, Desulfobulbus in Deltaproteobacteria appeared to be the putative sulfate reducing bacteria responsible for the Hg-methylation. We further discussed the effect of vegetation on the distribution of microbial communities related to Hg-methylation.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFM.B51I2356H
- Keywords:
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- 3339 Ocean/atmosphere interactions;
- ATMOSPHERIC PROCESSES;
- 0409 Bioavailability: chemical speciation and complexation;
- BIOGEOSCIENCES;
- 0414 Biogeochemical cycles;
- processes;
- and modeling;
- BIOGEOSCIENCES;
- 0461 Metals;
- BIOGEOSCIENCES