Assessing N2 fixation in estuarine mangrove soils

Shiau, Yo‐Jin; Lin, Ming-Fen; Tan, Chen-Chung; Tian, Guangming; Chiu, Chih‐Yu

doi:10.1016/j.ecss.2017.03.005

Cited by 14 publications

(11 citation statements)

References 33 publications

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“…The hypothesis that fits all the geochemical observations is that the sediments and water column of the CMP are hot spots for microbes that fix nitrogen during sulfate reduction. The only probable explanation for low δ 15 N values in this area is N‐fixation, and it is well documented that S‐reducers in mangrove ecosystems also fix N (Romero et al, ; Shiau et al, ). We suggest that the δ 34 S values are so high because the flushing in this part of the estuary is poor, forcing the microbial communities to reduce the heavier 34 S that they would otherwise preferentially avoid (e.g., Emery & Robinson, ).…”

Section: Discussionmentioning

confidence: 84%

“…In a mangrove ( Kandelia obovata ) forest in Taiwan, the soil nitrogenase activity increased from ambient rates of 1.74 ± 0.58 μmol C 2 H 4 m −2 hr −1 to potential rates of 171 ± 11 μmol C 2 H 4 m −2 hr −1 , supporting the idea that the N‐fixers are generally present in mangrove soils but their rate of fixation is limited by the availability of C sources. Salinity did not affect these rates (Shiau et al, ). Further, these rate observations are underestimates of potential fixation as they did not account for soil diatoms and cyanobacteria nor did they measure water column fixation.…”

Section: Discussionmentioning

confidence: 97%

“…Nitrogen fixation, which is the conversion of N 2 gas into bioavailable forms, is a dominant process in mangrove forests, even in urban areas, and fixation in mangrove sediments and tropical estuarine waters is correlated with the supply of organic matter and carbon rather than N availability (Bhavya et al, ; O'Neil & Capone, ; Shiau et al, ). Nitrogen fixation is associated with sulfate reduction, where the activity of nitrogenase, the enzyme responsible for N reduction, has been linked to sulfate‐reducing bacteria (Romero et al, ; Shiau et al, ). Fixation studies conducted in mangroves in Taiwan and Belize found that the addition of carbon increased soil nitrogenase activity dramatically.…”

Section: Discussionmentioning

confidence: 99%

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Unexpected Nitrogen Sources in a Tropical Urban Estuary

et al. 2020

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Tropical urban estuaries are severely understudied. Little is known about the basic biogeochemical cycles and dominant ecosystem processes in these waterbodies, which are often low lying and heavily modified. The San Juan Bay Estuary (SJBE) in San Juan, Puerto Rico, is an example of such a system. Over the past 80 years, a portion of the estuary has filled in, changing the hydrodynamics and negatively affecting water quality. Here we sought to document these changes using ecological and biogeochemical measurements of surface sediments and bivalves. Measurements of sediment physical characteristics, organic matter content, and stable isotope ratios (δ13C, δ15N, δ34S) illustrated the effects of the closure of the Caño Martín Peña (CMP) on the hydrology and water quality of the enclosed and semi‐enclosed parts of the estuary. The nitrogen stable isotope (δ15N) values were lowest in the CMP, the stretch of the SJBE that is characterized by waters with low dissolved oxygen and high fecal coliform concentrations. Despite this, the results of this study indicate that nitrogen (N) contributions from N‐fixing, sulfate‐reducing microbes may meet or even exceed contributions from urban runoff and sewage. While the importance of sulfate reducers in contributing N to mangrove ecosystems is well documented, this is the first indication that such processes could be dominant in an intensely urban system. It also underscores just how little we know about tropical coastal ecosystems in densely populated areas throughout the globe.

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Section: Discussionmentioning

confidence: 84%

Section: Discussionmentioning

confidence: 97%

Section: Discussionmentioning

confidence: 99%

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Unexpected Nitrogen Sources in a Tropical Urban Estuary

et al. 2020

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“…Moreover, studies are increasingly focusing on evaluating how microbial N 2 fixation contributes to mangrove forests. Microbial N 2 fixation rates can vary widely from 0 to 10.1 mmol N m −2 d −1 , depending on the mangrove forest's geographic location [7][8][9][10].…”

Section: Introductionmentioning

confidence: 99%

“…N 2 fixation also corresponds to soil P availability [13]. Using MoO 4 , a chemical that inhibits sulfatereducing bacteria (SRB) activity, as an inhibitor, several studies have further indicated that SRB can contribute over 50% of the total N 2 fixation in mangrove forests [3,9].…”

Section: Introductionmentioning

confidence: 99%

Composition and Activity of N2-Fixing Microorganisms in Mangrove Forest Soils

Shiau

Lin

Yam

et al. 2021

Forests

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Mangrove forests are considered to be a highly productive ecosystem, but they are also generally nitrogen (N)-limited. Thus, soil N2 fixation can be important for the stability of both mangrove ecosystem functions and upland N supply. This study evaluates the N2 fixation activity and composition of relevant microorganisms in two coastal mangrove forests—the Guandu mangrove in an upstream estuary and the Bali mangrove in a downstream estuary—using the acetylene reduction method, real-time polymerase chain reaction, and next-generation sequencing. The results demonstrated that ambient nitrogenase activity was higher in downstream mangrove forests (13.2–15.6 nmol hr−1 g−1 soil) than in upstream mangrove forests (0.2–1.4 nmol hr−1 g−1 soil). However, both the maximum potential nitrogenase activity and nitrogenase gene (nifH gene) copy number were found to be higher in the upstream than in the downstream mangrove forests, implying that the nitrogenase activity and diazotrophic abundance may not necessarily be positively correlated. In addition, amended MoO4 (which inhibits the activity of sulfate-reducing bacteria in N2-fixation) yielded low nitrogenase activity, and sulfate-reducing bacteria made up 20–50% of the relative diazotrophic abundance in the mangrove forests, indicating that these bacteria might be the major active diazotrophs in this environment.

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Community Structure of Active Aerobic Methanotrophs in Red Mangrove (Kandelia obovata) Soils Under Different Frequency of Tides

et al. 2017

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Methanotrophs are important microbial communities in coastal ecosystems. They reduce CH emission in situ, which is influenced by soil conditions. This study aimed to understand the differences in active aerobic methanotrophic communities in mangrove forest soils experiencing different inundation frequency, i.e., in soils from tidal mangroves, distributed at lower elevations, and from dwarf mangroves, distributed at higher elevations. Labeling of pmoA gene of active methanotrophs using DNA-based stable isotope probing (DNA-SIP) revealed that methanotrophic activity was higher in the dwarf mangrove soils than in the tidal mangrove soils, possibly because of the more aerobic soil conditions. Methanotrophs affiliated with the cluster deep-sea-5 belonging to type Ib methanotrophs were the most dominant methanotrophs in the fresh mangrove soils, whereas type II methanotrophs also appeared in the fresh dwarf mangrove soils. Furthermore, Methylobacter and Methylosarcina were the most important active methanotrophs in the dwarf mangrove soils, whereas Methylomonas and Methylosarcina were more active in the tidal mangrove soils. High-throughput sequencing of the 16S ribosomal RNA (rRNA) gene also confirmed similar differences in methanotrophic communities at the different locations. However, several unclassified methanotrophic bacteria were found by 16S rRNA MiSeq sequencing in both fresh and incubated mangrove soils, implying that methanotrophic communities in mangrove forests may significantly differ from the methanotrophic communities documented in previous studies. Overall, this study showed the feasibility of CH DNA-SIP to study the active methanotrophic communities in mangrove forest soils and revealed differences in the methanotrophic community structure between coastal mangrove forests experiencing different tide frequencies.

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Assessing N2 fixation in estuarine mangrove soils

Cited by 14 publications

References 33 publications

Unexpected Nitrogen Sources in a Tropical Urban Estuary

Unexpected Nitrogen Sources in a Tropical Urban Estuary

Composition and Activity of N2-Fixing Microorganisms in Mangrove Forest Soils

Community Structure of Active Aerobic Methanotrophs in Red Mangrove (Kandelia obovata) Soils Under Different Frequency of Tides

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