The Dynamics of Plant-Mediated Sediment Oxygenation in Spartina anglica Rhizospheres—a Planar Optode Study

Ria de Aveiro is a mesotidal coastal lagoon with one of the largest continuous salt marshes in Europe. The objective of this work was to assess C, N and P stocks of Spartina maritima (low marsh pioneer halophyte) and Juncus maritimus (representative of mid-high marsh halophytes) combined with the contribution of Halimione portulacoides, Sarcocornia perennis, and Bolbochenous maritimus to the lagoon ≈4400 ha marsh area. A multivariate analysis (PCO), taking into account environmental variables and the annual biomass and nutrient dynamics, showed that there are no clear seasonal or spatial differences within low or mid-high marshes, but clearly separates J. maritimus and S. maritima marshes. Calculations of C, N and P stocks in the biomass of the five most representative halophytes plus the respective rhizosediment (25 cm depth), and taking into account their relative coverage, represents 252053 Mg C, 38100 Mg N and 7563 Mg P. Over 90% of the stocks are found within mid-high marshes. This work shows the importance of this lagoon’s salt marshes on climate and nutrients regulation, and defines the current condition concerning the ‘blue carbon’ and nutrient stocks, as a basis for prospective future scenarios of salt marsh degradation or loss, namely under SLR context.

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“…ref. 30). This is related to halophytes-specific processes31 and related to their seasonal changes in biomass and nutrient dynamics.…”

Section: Discussionmentioning

confidence: 99%

‘Blue Carbon’ and Nutrient Stocks of Salt Marshes at a Temperate Coastal Lagoon (Ria de Aveiro, Portugal)

Sousa

Santos

Silva

et al. 2017

Sci Rep

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“…The use of planar optode technology, in combination with rhizoboxes, facilitates the quantitative monitoring of temporal and spatial dynamics of O 2 and CO 2 around individual roots with minimal disturbance of the biomass and biogeochemical gradients (Blossfeld et al ., ). In the last two decades, planar O 2 optodes have rendered possible the recording of O 2 distribution in sediments and soils (Glud et al ., ; Holst et al ., ), and planar optode technology is slowly gaining a foothold in research on rhizosphere O 2 dynamics (Jensen et al ., ; Frederiksen & Glud, ; Askaer et al ., ; Minett et al ., ; Jovanovic et al ., ; Koop‐Jakobsen & Wenzhöfer, ; Larsen et al ., ; Han et al ., ; Koop‐Jakobsen et al ., ). In comparison, planar optode investigations of CO 2 are still in their infancy (Santner et al ., ), and studies on CO 2 dynamics in rhizospheres are still very sparse.…”

Section: Introductionmentioning

confidence: 97%

Dynamics of oxygen and carbon dioxide in rhizospheres of Lobelia dortmanna – a planar optode study of belowground gas exchange between plants and sediment

et al. 2018

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Root-mediated CO uptake, O release and their effects on O and CO dynamics in the rhizosphere of Lobelia dortmanna were investigated. Novel planar optode technology, imaging CO and O distribution around single roots, provided insights into the spatiotemporal patterns of gas exchange between roots, sediment and microbial community. In light, O release and CO uptake were pronounced, resulting in a distinct oxygenated zone (radius: c. 3 mm) and a CO -depleted zone (radius: c. 2 mm) around roots. Simultaneously, however, microbial CO production was stimulated within a larger zone around the roots (radius: c. 10 mm). This gave rise to a distinct pattern with a CO minimum at the root surface and a CO maximum c. 2 mm away from the root. In darkness, CO uptake ceased, and the CO -depleted zone disappeared within 2 h. By contrast, the oxygenated root zone remained even after 8 h, but diminished markedly over time. A tight coupling between photosynthetic processes and the spatiotemporal dynamics of O and CO in the rhizosphere of Lobelia was demonstrated, and we suggest that O -induced stimulation of the microbial community in the sediment increases the supply of inorganic carbon for photosynthesis by building up a CO reservoir in the rhizosphere.

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“…Moreover, bacteria can assimilate OM from multiple sources and decomposition rates and pathways are affected by local plant communities. Submerged grasses, macroalgae, and microalgae contribute directly to whole‐pond respiration rates and influence sediment bacteria by producing labile OM and altering redox conditions (Holmer and Nielsen ; Koop‐Jakobsen and Wenzhöfer ; Spivak and Reeve ). In addition, marine algae and marsh grass detritus washed into ponds can be deposited to sediments and stimulate respiration.…”

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confidence: 99%

Shallow ponds are biogeochemically distinct habitats in salt marsh ecosystems

Spivak

Gosselin

Sylva

2018

Limnology & Oceanography

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Runaway expansion of shallow ponds can catalyze the conversion of vegetated marshes into open water environments. Predicting how this transition affects ecosystem functioning is difficult because little is known about pond biogeochemistry. We characterized sediment organic matter sources and transformations in three ponds with different plant communities, over alternating periods of tidal isolation and flushing, during summer and fall, using a combination of stable isotopes, lipid biomarkers, and benthic fluxes. Sediment respiration rates (1.66 ± 0.09 mmol C m−2 d−1 to 28.53 ± 7.76 mmol C m−2 d−1) were comparable to shallow estuaries and driven by sulfate reduction. Rates varied across ponds, reflecting differences in summertime Ruppia maritima and macroalgae abundances, but were similar between seasons. Interactions between aboveground plant and sediment bacterial communities translated into distinct biogeochemical processes across the three ponds. Tidal isolation and summer weather intensified plant and bacterial community effects on pond carbon dynamics, resulting in algal biomass and lipid δ13C values that were 3–12‰ enriched, compared to nearby habitats. Surface sediment organic matter mainly derived from pond microalgae and was compositionally distinct from tidal creeks and marshes. Surprisingly, sediment bacteria were not tightly coupled to benthic microalgae but decomposed multiple carbon sources in surface sediments and became increasingly reliant on buried peat at deeper horizons. Pond development over time could largely be explained by sediment respiration and the simultaneous accretion of the surrounding marsh platform. The role of decomposition in pond expansion is consistent with previous assessments based on whole‐pond metabolism rates. Consequently, future pond expansion could alter ecosystem biogeochemistry and reduce carbon storage.

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The Dynamics of Plant-Mediated Sediment Oxygenation in Spartina anglica Rhizospheres—a Planar Optode Study

Cited by 53 publications

References 43 publications

‘Blue Carbon’ and Nutrient Stocks of Salt Marshes at a Temperate Coastal Lagoon (Ria de Aveiro, Portugal)

‘Blue Carbon’ and Nutrient Stocks of Salt Marshes at a Temperate Coastal Lagoon (Ria de Aveiro, Portugal)

Dynamics of oxygen and carbon dioxide in rhizospheres of Lobelia dortmanna – a planar optode study of belowground gas exchange between plants and sediment

Shallow ponds are biogeochemically distinct habitats in salt marsh ecosystems

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