Does an ‘iron gate’ carbon preservation mechanism exist in organic–rich wetlands?

Wang, Hongjun; River, Mark; Richardson, Curtis J.

doi:10.1016/j.soilbio.2019.04.011

Cited by 21 publications

(13 citation statements)

References 11 publications

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“…33 Recent investigations, however, refuted the "iron gate" in organic-rich wetlands. 76 In addition, McGivern et al identified nine enzyme groups involved in anoxic phenol metabolism by a multiomics investigation of the phenol metabolisms in a wetland in the USA which are not included under the umbrella term "phenol oxidases". 60 As a consequence, these contradictory results led to the conclusion that the "latch mechanism" in combination with counteractive mechanisms (such as the "iron gate" 59 or anoxic phenol metabolism 60 ) simultaneously controls carbon cycling within wetlands, with the relative potency of each mechanism depending on various factors, 77,78 including the composition of the wetland soil, 59 the wetland type, 79 the wetland vegetation, 59,80 the organic matter composition, the concentration of phenolic compounds, 68 the duration of drought 59 as well as the hydrological legacy, 81 seasonal variations, 47 the pH 80,82,83 and the temperature of the respective wetland ecosystem, 82,83 and the presence of enzyme inhibitors.…”

Section: Critical Assessment Of the Global Impact Of The "Latch Mecha...mentioning

confidence: 99%

“… 33 Recent investigations, however, refuted the “iron gate” in organic-rich wetlands. 76 In addition, McGivern et al identified nine enzyme groups involved in anoxic phenol metabolism by a multiomics investigation of the phenol metabolisms in a wetland in the USA which are not included under the umbrella term “phenol oxidases”. 60 …”

Section: Introductionmentioning

confidence: 99%

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The Novel Role of Tyrosinase Enzymes in the Storage of Globally Significant Amounts of Carbon in Wetland Ecosystems

Panis

Rompel

2022

Environ. Sci. Technol.

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Over the last millennia, wetlands have been sequestering carbon from the atmosphere via photosynthesis at a higher rate than releasing it and, therefore, have globally accumulated 550 × 10 15 g of carbon, which is equivalent to 73% of the atmospheric carbon pool. The accumulation of organic carbon in wetlands is effectuated by phenolic compounds, which suppress the degradation of soil organic matter by inhibiting the activity of organic-matter-degrading enzymes. The enzymatic removal of phenolic compounds by bacterial tyrosinases has historically been blocked by anoxic conditions in wetland soils, resulting from waterlogging. Bacterial tyrosinases are a subgroup of oxidoreductases that oxidatively remove phenolic compounds, coupled to the reduction of molecular oxygen to water. The biochemical properties of bacterial tyrosinases have been investigated thoroughly in vitro within recent decades, while investigations focused on carbon fluxes in wetlands on a macroscopic level have remained a thriving yet separated research area so far. In the wake of climate change, however, anoxic conditions in wetland soils are threatened by reduced rainfall and prolonged summer drought. This potentially allows tyrosinase enzymes to reduce the concentration of phenolic compounds, which in turn will increase the release of stored carbon back into the atmosphere. To offer compelling evidence for the novel concept that bacterial tyrosinases are among the key enzymes influencing carbon cycling in wetland ecosystems first, bacterial organisms indigenous to wetland ecosystems that harbor a TYR gene within their respective genome ( tyr + ) have been identified, which revealed a phylogenetically diverse community of tyr + bacteria indigenous to wetlands based on genomic sequencing data. Bacterial TYR host organisms covering seven phyla (Acidobacteria, Actinobacteria, Bacteroidetes, Firmicutes, Nitrospirae, Planctomycetes, and Proteobacteria) have been identified within various wetland ecosystems (peatlands, marshes, mangrove forests, bogs, and alkaline soda lakes) which cover a climatic continuum ranging from high arctic to tropic ecosystems. Second, it is demonstrated that (in vitro) bacterial TYR activity is commonly observed at pH values characteristic for wetland ecosystems (ranging from pH 3.5 in peatlands and freshwater swamps to pH 9.0 in soda lakes and freshwater marshes) and toward phenolic compounds naturally present within wetland environments ( p -coumaric acid, gallic acid, protocatechuic acid, p -hydroxybenzoic acid, caffeic acid, catechin, and epicatechin). Third, analyzing the available data confirmed that bacterial host organisms tend to exhibit in vitro growth optima at pH values similar to their respective wetland habitats. Based on these findings, it is concluded that, following increased aeration of previously anoxic wetland soils due to climate change, TYRs are among th...

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Section: Critical Assessment Of the Global Impact Of The "Latch Mecha...mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

The Novel Role of Tyrosinase Enzymes in the Storage of Globally Significant Amounts of Carbon in Wetland Ecosystems

Panis

Rompel

2022

Environ. Sci. Technol.

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“…This soil C protection mechanism has been observed in both dominantly aerobic and anaerobic systems, including sediments, C‐rich paddy soils, and upland soils (Kögel‐Knabner et al., 2010; Lalonde et al., 2012; Wagai & Mayer, 2007). The negative relationship observed here suggests that reactive organo‐Fe complexes are not the predominant mechanism of soil C protection in drained soils (Wang, River, & Richardson, 2019). Alternatively, organo‐Fe complexes may also be utilized by microbial Fe reducers in these soils following depletion of other reactive Fe pools (i.e., Fe CA ) when soils experience reducing conditions associated with rainfall or irrigation events.…”

Section: Discussionmentioning

confidence: 83%

Mineralogical associations with soil carbon in managed wetland soils

Anthony

Silver

2020

Global Change Biology

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“…This reflects the relatively low susceptibility of mire DOM to microbial breakdown (Ågren et al, 2008; Berggren et al, 2009; M. Chen & Jaffé, 2014). While iron may stabilize soil OM under oxic condition (e.g., iron associated lignin), it may have negligible or even positive impacts on degradation in some organic‐rich hydric soils (Emsens et al, 2016; Wang et al, 2019), and fluctuating redox conditions could also be important for bioavailability (C. Chen et al, 2020; Hall et al, 2015). This could suggest that iron may provide protection against biodegradation of OM in oxic waters and perhaps support a longer‐term storage of OM in aquatic sediments (Lalonde et al, 2012).…”

Section: Discussionmentioning

confidence: 99%

Particles and Aeration at Mire‐Stream Interfaces Cause Selective Removal and Modification of Dissolved Organic Matter

et al. 2020

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Peatlands are dominant sources of dissolved organic matter (DOM) to boreal inland waters and play important roles in the aquatic carbon cycle. Yet before peat-derived DOM enters aquatic networks, it needs to pass through peat-stream interfaces that are often characterized by transitions from anoxic or hypoxic to oxic conditions. Aeration at these interfaces may trigger processes that impact the DOM pool, and its fate downstream. Here we experimentally assessed how the aeration of iron-and organic-rich mire-waters influences biodegradation, particle-formation, and modification of DOM. In addition, we investigated how suspended peat-derived particles from mires may influence these processes. We found that within 5 days of aeration, 20% of the DOM transformed into particulate organic matter (POM). This removal was likely due to combination of mechanisms including coprecipitation with oxidized iron, aggregation, and DOM-adsorption onto peat-derived particles. Peat-derived particles promoted microbial activity, but biodegradation was a minor loss mechanism of DOM removal. Interestingly, microbial respiration accounted for only half of the oxygen loss, suggesting substantial nonrespiratory oxygen consumption. The differences observed in DOM characteristics between anoxic and aerated treatments suggest that hydrophilic, aromatic DOM coprecipitated with iron oxides in aerated samples, and the corresponding C:N analysis of generated POM revealed that these organic species were nitrogen-poor. Meanwhile, POM formed via adsorption onto peat-derived particles generated from nonaromatic DOM and more nitrogen-rich species. Hence, selective removal of DOM, dissolved iron, and thus oxygen may be important and overlooked processes in mire-dominated headwater systems. Plain Language Summary Substantial amounts of dissolved organic matter are discharged from boreal peatlands into small streams and delivered to downstream rivers and lakes, impacting water quality, freshwater ecology, and the aquatic carbon cycle. About half of this dissolved organic matter is processed and removed during downstream transport, mainly via degradation and CO 2 emission, but also through particle formation and sedimentation. Less is known about the processing in upstream systems, where peat-water emerges into small streams. These peat-stream interfaces are characterized by rapid transitions from anoxic to oxic conditions. Since oxygen exposure may promote both microbial activity and chemical reactions, e.g., coprecipitation with iron, these interfaces might be critical locations for dissolved organic matter transformations. Here we experimentally study microbial and nonbiological processing of dissolved organic matter when anoxic mire-waters are aerated. We also assess how particles found in the peat-water may stimulate these processes. Our results suggest significant nonbiological particle formation and modification of the dissolved organic matter pool when anoxic waters from peatlands are first delivered to streams. In addition, we find that natural pa...

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Does an ‘iron gate’ carbon preservation mechanism exist in organic–rich wetlands?

Cited by 21 publications

References 11 publications

The Novel Role of Tyrosinase Enzymes in the Storage of Globally Significant Amounts of Carbon in Wetland Ecosystems

The Novel Role of Tyrosinase Enzymes in the Storage of Globally Significant Amounts of Carbon in Wetland Ecosystems

Mineralogical associations with soil carbon in managed wetland soils

Particles and Aeration at Mire‐Stream Interfaces Cause Selective Removal and Modification of Dissolved Organic Matter

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