Table 1 Hg impact on microbes and associated carbon and nitrogen cycling

From: Aligning global mercury mitigation with climate action

Cycle

Process

Ecosystem

Microbe

Hg Concentration

Hg Impact

Ref

Carbon cycle

Methanogenesis

Rice paddy

Methanobacteria

0.25–990

Increased CH4 emissions

33

Organic matter decomposition

Pasture field

Verrucomicrobiota; Fungi

0.25–36.1

Increased CO2 release due to Hg-tolerant decomposers

22

Syntrophic interactions

Rice paddy*

Sulfate-reducing bacteria; Geobacteraceae; Methanogens

5–50

Altered syntropy, with an increased abundance of methanogens and enhanced CH4 emissions

80

Nitrogen cycle

Nitrification

Vegetable field*

Ammonia-oxidizing bacteria

0–30

Significant reduction in abundance and nitrification rates

36

Rice paddy

Nitrospirota

1.11–29.07

Reduced \({{\mbox{NO}}}_{3}^{-}\) production due to Hg-induced abundance decline

18

Rice paddy and upland

Nitrospirota

0.27–52.4

Relative abundance decreased with elevated MeHg concentrations

81

Denitrification

Wheat-maize field*

Denitrifiers

0–100

Transient spikes in denitrification genes, nirS and nosZ

37

Rice paddy

Gemmatimonadota

4.86–28

Increased abundance under Hg stress, altering nitrogen retention

18

Cross-cycle feedback

Microbial stress adaptation

Cropland

General microbial community

2.40–420.7

Increased abundance and diversity after Hg exposure

82

Rice paddy

Pseudomonadota

1.11–29.07

Reduced microbial diversity at high Hg concentrations, notably Pseudomonadota for carbon/nitrogen cycling

18

Rice paddy and upland

Firmicutes; Bacteroidota

0.27–52.4

Positive correlation with Hg; shifts in decomposition and nitrogen cycling

81

Functional diversity loss

Forest*

General microbial community

0.03-32

High Hg basal respiration decreased; structural degradation

20

Rice paddy

General microbial community

0.27–588

Reduced microbial diversity under Hg stress, e.g., Planctomycetota and Actinomycetota

21

Community resilience

Tropical forest

General microbial community

3.20–32

Reduced microbial diversity under high Hg stress

19

Agricultural floodplain

General microbial community

0.25–36

Increased basal respiration and nitrification rate at high Hg concentrations; carbon and nitrogen cycling were slightly hampered

47

  1. “*” indicates spiked experiments. All Latin names listed above are updated following recent bacterial taxonomy revisions and thus may be slightly different from what they are in the original articles. Concentration unit: μg/g dry wt. in soils or sediments.
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