Rapid cycling of recently fixed carbon in a Spartina alterniflora system: a stable isotope tracer experiment

Spivak, Amanda C.; Reeve, Jennifer R.

doi:10.1007/s10533-015-0115-2

Cited by 22 publications

(26 citation statements)

References 69 publications

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“…f). Both bacterial markers were slightly depleted relative to PUFAs, particularly in ponds 1 and 2, enriched relative to marsh soils (−17.3 ± 1.5‰ to −18.9 ± 0.3‰; Wang et al ; Spivak and Reeve ), and overlapped with emergent grasses, BMA biomass, and suspended POC (Figs. a,b, d–f).…”

Section: Resultsmentioning

confidence: 94%

“…Algal and microbial (PUFA, SCFA) contributions to SOM were higher in ponds than marshes, but lower than tidal creeks (Pascal et al ; Spivak and Reeve ; Spivak and Ossolinski ). Bacterial lipids (BrFA, 10‐methyl C16) made up a similar fraction of total PLFAs in pond and tidal creek sediments, but were relatively more abundant in marsh sediments (Pascal et al ; Spivak and Reeve ; Spivak and Ossolinski ). Unlike many shallow systems, pond surface SOM composition and fluxes were similar in summer and fall (Figs.…”

Section: Discussionmentioning

confidence: 97%

“…b,c, d–f). Bacteria were not entirely reliant on the underlying peat either, as δ 13 C of BrFA and 10‐methyl C16 were slightly more enriched than marsh soils (−17.3 ± 1.5‰ to −18.9 ± 0.3‰) (Wang et al ; Spivak and Reeve ). Isotopic offsets between bacterial lipids and OM sources suggest that communities may have assimilated more carbon from peat (Δ δ BrFA vs. soil: 2.77 ± 0.5‰, 1.91 ± 0.4‰) than microalgae (Δ δ BrFA vs. PUFA: 5.17 ± 0.5‰, 5.77 ± 0.5‰) in ponds 1 and 2, respectively, but decomposed both OM sources in similar proportions in pond 3 (Δ δ BrFA vs. soil and PUFA: 2.65 ± 0.4‰ and 1.70 ± 0.6‰; Fig.…”

Section: Discussionmentioning

confidence: 99%

“…Lipid biomarker compounds were extracted from SOM cores using a modified Bligh and Dyer () method (Spivak and Reeve ). Sediments were extracted with a methanol : chloroform : phosphate buffer saline mixture (2 : 1 : 0.8, v : v : v) using a microwave‐accelerated reaction system (MARS6); samples were heated to 80°C for 10 min with continuous stirring.…”

Section: Methodsmentioning

confidence: 99%

“…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%

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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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Section: Resultsmentioning

confidence: 94%

Section: Discussionmentioning

confidence: 97%

Section: Discussionmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

mentioning

confidence: 99%

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Shallow ponds are biogeochemically distinct habitats in salt marsh ecosystems

Spivak

Gosselin

Sylva

2018

Limnology & Oceanography

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Carbon dioxide fluxes reflect plant zonation and belowground biomass in a coastal marsh

et al. 2016

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Coastal wetlands are major global carbon sinks; however, they are heterogeneous and dynamic ecosystems. To characterize spatial and temporal variability in a New England salt marsh, greenhouse gas (GHG) fluxes were compared among major plant‐defined zones during growing seasons. Carbon dioxide (CO2) and methane (CH4) fluxes were compared in two mensurative experiments during summer months (2012–2014) that included low marsh (Spartina alterniflora), high marsh (Distichlis spicata and Juncus gerardii‐dominated), invasive Phragmites australis zones, and unvegetated ponds. Day‐ and nighttime fluxes were also contrasted in the native marsh zones. N2O fluxes were measured in parallel with CO2 and CH4 fluxes, but were not found to be significant. To test the relationships of CO2 and CH4 fluxes with several native plant metrics, a multivariate nonlinear model was used. Invasive P. australis zones (−7 to −15 μmol CO2·m−2·s−1) and S. alterniflora low marsh zones (up to −14 μmol CO2·m−2·s−1) displayed highest average CO2 uptake rates, while those in the native high marsh zone (less than −2 μmol CO2·m−2·s−1) were much lower. Unvegetated ponds were typically small sources of CO2 to the atmosphere (<0.5 μmol CO2·m−2·s−1). Nighttime emissions of CO2 averaged only 35% of daytime uptake in the low marsh zone, but they exceeded daytime CO2 uptake by up to threefold in the native high marsh zone. Based on modeling, belowground biomass was the plant metric most strongly correlated with CO2 fluxes in native marsh zones, while none of the plant variables correlated significantly with CH4 fluxes. Methane fluxes did not vary between day and night and did not significantly offset CO2 uptake in any vegetated marsh zones based on sustained global warming potential calculations. These findings suggest that attention to spatial zonation as well as expanded measurements and modeling of GHG emissions across greater temporal scales will help to improve accuracy of carbon accounting in coastal marshes.

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