Short-term fate of intertidal microphytobenthos carbon under enhanced nutrient availability: a &amp;lt;sup&amp;gt;13&amp;lt;/sup&amp;gt;C pulse-chase experiment

Riekenberg, Philip M.; Oakes, Joanne M.; Eyre, Bradley D.

doi:10.5194/bg-15-2873-2018

Cited by 12 publications

(21 citation statements)

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“…DIC and nutrients that arose from bacterial remineralization likely supported MPB productivity and were recycled within the sediment by co-metabolism within the microbial community. Increased microbial recycling resulted in increased contribution of uncharacterized material to 13 C within sediment OM in the elevated treatment 32 . Therefore, inclusion of the byproducts of remineralization from sediment OM (DOC) allows for more complete accounting of the C arising from PEs, especially in highly productive systems.…”

Section: Discussionmentioning

confidence: 99%

“…The pulse of labile MPB-C was strongly retained within sediment OM in both treatments across 3.5 d (Fig. 3), with relatively low effluxes for DI 13 C and DO 13 C across this time resulting in relatively long estimates for MPB-C turnover (419 d ambient vs 199 d elevated) 32 . Strong short-term retention of MPB-C in both treatments indicates that the microbial community readily utilized the newly produced labile 13 C and subsequently recycled respired DI 13 C to support productivity.…”

Section: Characterization Of Exported Docmentioning

confidence: 96%

“…We applied 13 C to MPB in situ to track the production of algal carbon that occurred during a single tidal minimum within the intertidal setting in order to track production and processing of MPB derived C. Application of stable isotope (SI) tracer material (99% NaH 13 CO 3 ) during a tidal low allowed for incorporation across ~ 4 hours of 1549±140 µmol 13 C m -2 into sediment OC followed by significant flushing of non-incorporated 13 C from the sediment during tidal inundation of the site as confirmed by loss of 99.0% of the material in the label application based on measured incorporation in the sediment within the initial cores 32 . Of the 13 C incorporated into sediment OC, ~46% or 716 µmol 13 C is expected to be in the form of carbohydrates as calculated from uptake rates for 13 C presented in Oakes, et al 19 for mannose, fucose, rhamnose, galactose, glucose, xylose, and OC.…”

Section: Labeling Of Mpb Exudatesmentioning

confidence: 98%

“…Initial samples were taken 30 min after closure of the lids, dark samples were taken after ~12 hours incubation with no light, and light samples were taken 3 hours after illumination after the end of the dark sampling. Oxygen measurements were taken for the overlying water with oxygen saturation never occurring below 86.1% during the dark incubations (oxygen fluxes presented in Riekenberg, et al 32 ). DIC and DOC concentrations and δ 13 C values (‰) were measured via continuous-flow wet oxidation isotope-ratio mass spectrometry using an Aurora 1030W total organic C analyzer coupled to a Thermo Delta V isotope ratio mass spectrometer (IRMS) 42 .…”

Section: Benthic Flux Incubationsmentioning

confidence: 99%

“…Laboratory core incubations allowed explicit control of nutrient additions, reducing the variability in water quality that occurs naturally across the tidal cycle. Pulsed applications of nutrients were used to mimic a range of nutrient concentrations without exceeding sediment capacity for uptake32 . NH 4 + pulses were completely taken up within 24 h of application.…”

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confidence: 99%

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Shining light on priming in euphotic sediments: Nutrient enrichment stimulates export of stored organic matter

Riekenberg¹,

Oakes²,

Eyre³

2020

Preprint

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Estuarine sediments are important sites for the interception, processing and retention of organic matter, prior to its export to the coastal oceans. Stimulated microbial co-metabolism (priming) potentially increases export of refractory organic matter through increased production of hydrolytic enzymes. By using the microphytobenthos community to directly introduce a pulse of labile carbon into sediment, we traced a priming effect and assessed the decomposition and export of pre-existing organic matter. We show enhanced efflux of pre-existing carbon from intertidal sediments enriched with water column nutrients. Nutrient enrichment increased production of labile microphytobenthos-carbon which stimulated degradation of previously unavailable organic matter and led to increased liberation of “old” (6855 ± 120 years BP) refractory carbon as dissolved organic carbon. These enhanced DOC effluxes occurred at a scale that decreases estimates for global organic carbon burial in coastal systems and should be considered as an impact of eutrophication on estuarine carbon budgets.

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Section: Discussionmentioning

confidence: 99%

Section: Characterization Of Exported Docmentioning

confidence: 96%

Section: Labeling Of Mpb Exudatesmentioning

confidence: 98%

Section: Benthic Flux Incubationsmentioning

confidence: 99%

mentioning

confidence: 99%

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Shining light on priming in euphotic sediments: Nutrient enrichment stimulates export of stored organic matter

Riekenberg¹,

Oakes²,

Eyre³

2020

Preprint

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Hot spots drive uptake and short‐term processing of organic and inorganic carbon and nitrogen in intertidal sediments

Riekenberg,

Eyre,

van der Meer

et al. 2024

Limnology & Oceanography

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This study uses dual‐labeled (13C and 15N) stable isotope applications to examine microbial uptake and short‐term processing of carbon (C) and nitrogen (N) from organic and inorganic compounds in subtropical intertidal sediment. Four treatment applications were applied: (1) algal dissolved organic matter (DOM), (2) amino acid mixture, (3) glucose and , and (4) NaHCO3 and to assess bioavailability effects on processing (1 vs. 2) and short‐term processing for OM fixed via microphytobenthos only (pennate diatom dominated) (4) vs. material taken up by the entire microbial community (3) across 24 h. 13C from algal‐DOM was preferentially used by the microbial community vs. 15N. At 24 h more 13C from algal‐DOM remained in microbial biomass indicating use of labeled precursor molecules to form biomass. Conversely, 13C from the amino acid treatment was not incorporated into biomass and was either rapidly respired to DIC or discarded as the in situ microbial community preferentially used and retained 15N from amino acids. Short‐term export of 13C as CO2 from glucose was lower than from microphytobenthos‐C, while retention of 15N from was similar between treatments (3 and 4) despite doubling the application N concentration, suggesting potentially higher glucose‐stimulated 15N export via nitrification–denitrification that was not confirmed via flux measurements in this study. Despite careful site selection for similar tidal exposure and sediment types among the three estuaries, the uptake and processing of labeled substrate varied substantially between replicates and sites which challenged traditional statistical analysis. Disproportionate processing of substrates occurring in sediment hotspots of microbial activity can cause variability spanning orders of magnitude which was found to be widespread through comparison of our results against 19 previous studies in intertidal settings. Development of robust analytical techniques to handle variability from abiotic and biotic factors will allow greater clarity surrounding in situ biogeochemical processing in intertidal environments.

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Adapting an elemental analyser to perform high‐temperature catalytic oxidation for dissolved organic carbon measurements in water

Carvalho

2022

Rapid Comm Mass Spectrometry

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Rationale Many laboratories employ elemental analyzers (EAs) coupled to isotope ratio mass spectrometers (IRMSs) to measure carbon stable isotope ratios (δ13C) in solid samples. Dissolved organic carbon (DOC) in most natural water samples cannot be analyzed using this approach unless time‐consuming preconcentration is employed. Methods An EA‐IRMS can be used to measure DOC δ13C in natural waters without the need for sample preconcentration by employing high‐temperature catalytic oxidation. An autosampler injects water into the EA reactor at 680°C filled with platinum catalyst beads, where all carbon is converted to CO2. Remaining water and halides are removed, while CO2 is trapped in a cryotrap and later released to the IRMS. Results Measurements were accurate (deviation <0.3‰ compared to solid sample measurements) and precise (error of 0.3‰ for concentrations ≥46 μM). Blanks were present and accounted for. Salinity up to seawater level did not affect accuracy or precision, but limited the number of samples that could be run before cleaning of the reactor was needed. DOC δ13C in a river/estuary varied between −25.7 and −23.2‰, with higher values for waters with higher salinity, as expected. Deep‐sea water reference material had a value of −22.9 ± 0.5‰, very similar to those found in recent reports employing similar techniques. Conclusion Adapting an EA is a feasible approach for the measurement of DOC δ13C in natural waters. The low cost and simplicity of the system allow its use in any laboratory already equipped with EA‐IRMS.

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Short-term fate of intertidal microphytobenthos carbon under enhanced nutrient availability: a <sup>13</sup>C pulse-chase experiment

Cited by 12 publications

References 73 publications

Shining light on priming in euphotic sediments: Nutrient enrichment stimulates export of stored organic matter

Shining light on priming in euphotic sediments: Nutrient enrichment stimulates export of stored organic matter

Hot spots drive uptake and short‐term processing of organic and inorganic carbon and nitrogen in intertidal sediments

Adapting an elemental analyser to perform high‐temperature catalytic oxidation for dissolved organic carbon measurements in water

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