Global overview on nitrogen dynamics in mangroves and consequences of increasing nitrogen availability for these systems

Reis, Carla Roberta Gonçalves; Nardoto, Gabriela Bielefeld; Oliveira, Rafael S.

doi:10.1007/s11104-016-3123-7

Cited by 92 publications

(51 citation statements)

References 149 publications

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“…N 2 fixation was one of the most dominant pathways compared to other N-cycling processes associated with fiddler crab microbiota, suggesting that this characteristic benthic invertebrate has a potentially relevant role in mangrove ecosystems as a vector of newly fixed N to the surrounding environment. The study area is a system where N 2 fixation is an important conduit for bioavailable N 39 . Therefore, fixed N is an essential element in mangrove food webs, including detritus-feeding fiddler crabs.…”

Section: +68mentioning

confidence: 99%

N2 fixation dominates nitrogen cycling in a mangrove fiddler crab holobiont

Žilius

Bonaglia

Broman

et al. 2020

Sci Rep

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Mangrove forests are among the most productive and diverse ecosystems on the planet, despite limited nitrogen (N) availability. Under such conditions, animal-microbe associations (holobionts) are often key to ecosystem functioning. Here, we investigated the role of fiddler crabs and their carapaceassociated microbial biofilm as hotspots of microbial N transformations and sources of N within the mangrove ecosystem. 16S rRNA gene and metagenomic sequencing provided evidence of a microbial biofilm dominated by Cyanobacteria, Alphaproteobacteria, Actinobacteria, and Bacteroidota with a community encoding both aerobic and anaerobic pathways of the N cycle. Dinitrogen (N 2) fixation was among the most commonly predicted process. Net N fluxes between the biofilm-covered crabs and the water and microbial N transformation rates in suspended biofilm slurries portray these holobionts as a net N 2 sink, with N 2 fixation exceeding N losses, and as a significant source of ammonium and dissolved organic N to the surrounding environment. N stable isotope natural abundances of fiddler crab carapace-associated biofilms were within the range expected for fixed N, further suggesting active microbial N 2 fixation. These results extend our knowledge on the diversity of invertebratemicrobe associations, and provide a clear example of how animal microbiota can mediate a plethora of essential biogeochemical processes in mangrove ecosystems. Among coastal ecosystems, mangrove forests are of great importance as they account for three quarters of the tropical coastline and provide different ecosystem services 1,2. Mangrove ecosystems generally act as a net sink of carbon, although they release organic matter to the sea in the form of dissolved refractory macromolecules, leaves, branches and other debris 3,4. In pristine environments, mangroves are among the most productive ecosystems on the planet, despite growing in tropical waters that are often nutrient depleted 5. The refractory nature of the organic matter produced and retained in mangroves can slow the recycling of nutrients, particularly of nitrogen (N) 3,6. Nitrogen limitation in such systems may be overcome by microbial dinitrogen (N 2) fixation when combined with high rates of bioturbation by macrofauna 7,8. Bioturbation by macrofauna affect N availability and multiple N-related microbial processes through sediment reworking, burrow construction and bioirrigation, feeding and excretion 9. Macrofauna mix old and fresh organic matter, extend oxic-anoxic sediment interfaces, increase the availability of energy-yielding electron acceptors and increase N turnover via direct excretion 10,11. Thus, macrofauna may alleviate N limitation by priming the remineralization of refractory N, reducing plants-microbe competition 12,13. Such activity ultimately promotes N-recycling, plant assimilation and high N retention, as well as favours it loss by stimulating coupled nitrification and denitrification 14. Mangrove sediments are highly bioturbated by decapods such as crabs 15. Crab populations ...

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Section: +68mentioning

confidence: 99%

N2 fixation dominates nitrogen cycling in a mangrove fiddler crab holobiont

Žilius

Bonaglia

Broman

et al. 2020

Sci Rep

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“…In oyster reefs, however, anammox rates have not yet been reported, to the best of our knowledge. Mangroves (Cao et al, 2017;Reis et al, 2017) and salt-marshes (Sousa et al, 2012) have also been reported to support very high anammox and denitrification rates, particularly when receiving high nitrate inputs (Koop-Jakobsen and Giblin, 2010;Reis et al, 2017). Hence, a high capacity for removal of reactive nitrogen, through both burial and, particularly, removal of reactive nitrogen as N 2 gas, is a key, but hitherto insufficiently realized ecosystem service of seagrass meadows (Reynolds et al, 2016;Zarnoch et al, 2017), oyster reefs (Cerco and Noel, 2007;Kellogg et al, 2014;Caffrey et al, 2016;Smyth et al, 2016), mangroves (Valiela and Cole, 2002;Cao et al, 2017;Reis et al, 2017) and salt-marshes (Valiela and Cole, 2002;Koop-Jakobsen and Giblin, 2010;Sousa et al, 2012).…”

Section: Interventions To Enhance Nitrogen Emissions As Nmentioning

confidence: 99%

Intervention Options to Accelerate Ecosystem Recovery From Coastal Eutrophication

Duarte

2018

Front. Mar. Sci.

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Three decades following the onset of efforts to revert widespread eutrophication of coastal ecosystems, evidence of improvement of ecosystem status is growing. However, cumulative pressures have developed in parallel to eutrophication, including those associated with climate change, such as warming, deoxygenation, ocean acidification and increased runoff. These additional pressures risk countering efforts to mitigate eutrophication and arrest coastal ecosystems in a state of eutrophication despite the efforts and significant resources already invested to revert coastal eutrophication. Here we argue that the time has arrived for a broader, more comprehensive approach to intervening to control eutrophication. Options for interventions include multiple levers controlling major pathways of nutrient budgets of coastal ecosystems, i.e., nutrient inputs, which is the intervention most commonly deployed, nutrient export, sequestration in sediments, and emissions of nitrogen to the atmosphere as N 2 gas (denitrification). The levers involve local-scale hydrological engineering to increase flushing and nutrient export from (semi)enclosed coastal systems, ecological engineering such as sustainable aquaculture of seaweeds and mussels to enhance nutrient export and restoration of benthic habitats to increase sequestration in sediments as well as denitrification, and geo-engineering approaches including, with much precaution, aluminum injections in sediments. These proposed supplementary management levers to reduce eutrophication involve ecosystem-scale intervention and should be complemented with policy actions to protect benthic ecosystem components.

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“…Nitrogen isotope tracer techniques have been widely used to quantify nitrogen transformations in sediments (Kristensen et al, 1998;Reis et al, 2017;Rivera-Monroy & Twilley, 1996). However, analysis of stable multi-isotopes of nitrogen forms (e.g., 15 N and 18 O of nitrate, ammonium, and N 2 O) is rarely applied to define nitrogen source and cycling processes involved in the mangrove system.…”

Section: Introductionmentioning

confidence: 99%

Major Processes Shaping Mangroves as Inorganic Nitrogen Sources or Sinks: Insights From a Multidisciplinary Study

et al. 2019

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Mangrove wetlands support numerous ecosystem services including nutrient cycling and carbon sequestration and storage (blue carbon). Mangrove sediments may serve as a nitrogen source or sink to the hydrosphere and atmosphere at both regional and global scales. However, major mechanisms controlling the connection between the mangrove and the adjacent tidal creek (nitrogen cycling in sediments and outfluxing) remain unclear. A multidisciplinary study based on intensive investigation, incorporating detailed sediment profiling, multi‐isotopes analysis, sediment incubation, and microbiological identification was conducted in the Yunxiao mangrove reserve and Zhangjiang Estuary in southeast China. Here we show that mineralization and denitrification are major processes shaping mangroves as an ammonium source and nitrate sink. Enrichment of ammonium in pore water (10–40 cm in depth) likely resulted from strong ammonification with limited nitrification in the anaerobic sediments. Denitrification played a key role in nitrate removal from pore waters while producing N2O and N2. Decreasing δ15N‐N2O and associated δ15N:δ18O ratio suggested that most of the outgassing N2O was derived from incomplete denitrification in sediment pore water. Overall, there was a net export of dissolved inorganic nitrogen from mangroves toward the estuary in winter and spring but a net import to mangroves in summer and fall, mainly driven by tidal pumping with seasonal variation of bio‐uptake. These findings highlight the role of mangrove wetlands in regulating nutrient status and carbon budget in coastal areas.

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Global overview on nitrogen dynamics in mangroves and consequences of increasing nitrogen availability for these systems

Cited by 92 publications

References 149 publications

N2 fixation dominates nitrogen cycling in a mangrove fiddler crab holobiont

N2 fixation dominates nitrogen cycling in a mangrove fiddler crab holobiont

Intervention Options to Accelerate Ecosystem Recovery From Coastal Eutrophication

Major Processes Shaping Mangroves as Inorganic Nitrogen Sources or Sinks: Insights From a Multidisciplinary Study

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