DOI: 10.5061/dryad.xsj3tx9qt
title: Data from: CO2 fluxes in created and natural marshes in Sabine National Wildlife Refuge, Louisiana

description: This dataset consists of carbon (C) flux measurements in May, July and
 September 2017 collected in a 2-year old created and a nearby natural
 reference marsh in the Chenier Plain Region of Louisiana. The purpose of
 this study was to examine seasonal C fluxes, specifically, gross
 ecosystem production (GEP), ecosystem respiration (ER), and net ecosystem
 exchange (NEE) of CO2 in unvegetated and vegetated (Spartina alterniflora)
 areas of a 2-year old created marsh and Spartina alterniflora and Spartina
 patens communities in a ‘natural’ reference brackish marsh. We also
 collected plant biomass, sediment chlorophyll a concentrations, marsh
 elevation, soil nitrogen and organic matter and bulk density to test for
 relationships to carbon fluxes.
description: For this study, we tested seasonal carbon dioxide fluxes in
 unvegetated and newly vegetated (with <em>Spartina
 alterniflora</em>) areas of a 2-year old Created coastal marsh
 constructed in 2015 and in two vegetated communities (<em>Spartina
 alterniflora</em> and <em>Spartina patens</em>) a nearby
 ‘natural’ Reference marsh. The Reference marsh is representative of
 remnant brackish marshes in this system that have been subject to indirect
 human alterations of hydrology combined with natural changes to the
 system. The Reference marsh was dominated by a mix of species with stands
 of <em>S. alterniflora </em>at lower elevations and
 <em>S. patens</em> at higher elevations.  At the time of the
 study in 2017, the 2-year old Created marsh had large unvegetated areas
 and sparse clones of <em>S. alterniflora</em>, which expanded
 over the study period.  Clone patches of <em>S.
 alterniflora</em> in the Created marsh were heterogeneous, varying
 in size and biomass. <em>Carbon
 fluxes</em> Four habitats were the focus of this
 study, two representative of the Created marsh: (1) unvegetated sediments,
 where algae and microphytobenthos may be dominant primary producers
 (‘UC’); and (2) newly colonized <em>S. alterniflora
 </em>clones (‘SaC’); and two in the Reference marsh: (3)
 <em>S. alterniflora </em>(‘SaR’); and (4) <em>S. patens
 </em>(‘SpR’).  Carbon dioxide fluxes were measured in five replicate
 plots randomly located in each habitat type using the static chamber
 method (n = 5). Plots were at least 10 m apart. Gas chambers for the
 vegetated treatments consisted of a 30 cm<sup>3 </sup>acrylic
 base unit placed to a depth 10 cm below the surface approximately one
 month prior to the first set of measurements. The base unit was left in
 place throughout the study. In May, July and September 2017, one to three
 stackable 30 cm<sup>3 </sup>acrylic chambers were assembled to
 accommodate the height of the tallest vegetation in each of the five plots
 per habitat. A base of one top unit was used for the non-vegetated plots
 in the created marsh. To ensure an air-tight seal, a water-filled collar
 surrounded the base of each stackable unit to limit external gas diffusion
 into the chamber. Carbon dioxide concentration was measured using an EGM-4
 (PP Systems©, Amesbury, MA) infra-red gas analyzer to the nearest part per
 million at 1-minute intervals for 10 to 20 minutes or until the
 concentration was below the detection limit (~250 ppm). Net ecosystem
 exchange (NEE) was measured using transparent chambers while ecosystem
 respiration (ER) was measured using opaque chamber units. ER measurements
 were collected in the same plots following measurements of NEE and a 20
 minute equilibration period once opaque chambers were established to allow
 photosynthesis to cease. Net ecosystem exchange and ER
 have been found to vary with temperature and levels of photosynthetically
 active radiation (PAR). Therefore, temperature and PAR were measured along
 with CO<sub>2</sub> concentration using a probe attached to
 the EGM-4 (PP Systems©, Amesbury, MA).
 <em>CO<sub>2</sub>-flux
 calculations</em> NEE and ER were determined by
 linear regression of CO<sub>2</sub> change during the sampling
 interval where a strong linear slope was present. The slope of that
 regression was used as either the NEE (clear chamber) or ER (opaque
 chamber). The slope for NEE was only taken when full sunlight occurred in
 the sampling interval which is generally 1000 µmol
 m<sup>-2</sup>s<sup>-1</sup> or greater.
 The amount of CO<sub>2</sub> in the chamber at a
 given time<sub> </sub>was calculated as:
 <em>CO<sub>2 </sub></em><em>µmol
 =<sub> </sub>CO<sub>2 </sub>ppm /
 (22.4*(273+C)/273) * 27X </em> The coefficient X
 is the number of chamber units stacked at each plot. Each chamber unit
 contains 27 liters of air, and therefore X was multiplied by 27. The
 coefficient C is the temperature (°C) at the time of measurement. It
 should be noted that 22.4 is the molar volume of
 CO<sub>2</sub> at the pressure 1 ATM and 0°C. Our sites are at
 approximate sea level and thus are generally at 1 ATM pressure.
 Temperatures within the chambers were between 25 and 40°C and therefore
 temperature was corrected for in the above equation. 
 The GEP was calculated as: <em>GEP=
 -(NEE) + ER</em> Negative GEP and NEE indicates
 gross and net C uptake, respectively. It was assumed that respiration rate
 during the dark incubations was equal to the respiration rate during
 daylight conditions, but this may not be the case as leaf respiration
 tends to increase under dark conditions (Brooks and Farquhar, 1985;
 Kromer, 1995; Atkin et al. 1997; Schulz, 2003).   
 <em>Algal and plant biomass</em>
 To examine variation in algal biomass across treatments, sediment
 was collected adjacent to each gas exchange plot for chlorophyll
 <em>a</em> analysis during each sampling in May, July, and
 September. Chlorophyll<em> a</em> content was determined from
 the top 2 cm of sediment by using sonication and 90% acetone (modified
 from Welschmeyer, 1994). Approximately 0.2 g of the sampled sediment was
 placed in 90% acetone, centrifuged at 5000 X g for 5 minutes, and then
 sonicated.  Following sonication for 30 seconds, the samples were placed
 in a freezer for one day and then centrifuged again at 5000 X g for 5
 minutes again the next day. Chl <em>a</em> content was then
 measured using a fluorometer (Turner<strong> </strong>Designs
 TD-700<strong>)</strong>. Aboveground
 biomass was estimated using stem height and density measurements taken
 within the study plots in July and September 2017. The heights of up to 15
 randomly chosen stems was collected in each plot. Stem density was
 determined by counting the number of stems within 0.09
 m<sup>2</sup> for <em>S. alterniflora</em>, 0.01
 m<sup>2</sup> for <em>S. patens</em>. To estimate
 the biomass of <em>S. alterniflora </em>in the Reference
 marsh,<em> </em>the following equation was used for
 <em>Spartina alterniflora</em> in the region (Elsey-Quirk,
 unpublished data): <em>AB = - 2032 + 521(log
 height) + 136(log density)</em> The equation used
 for <em>S. alterniflora</em> in the Reference marsh was not
 used for <em>S. alterniflora </em>in the created marsh because
 the relationships between stem height, density and biomass may differ due
 to different soil or nutrient conditions. For <em>S. alterniflora
 </em>in the created marsh and <em>S. patens </em>in the
 Reference marsh a coefficient relating height and density was derived from
 data in a previous study in the same marshes where stem height, stem
 density, and biomass were measured (Abbott et al. 2019). The coefficient
 was determined from the average biomass divided by the product of stem
 density and average stem height. The equation used for
 <em>S. alterniflora</em> in the created marsh was:
 <em>AB = 0.0755(height)(density)</em>
 The equation used for <em>S. patens</em> in the
 Reference marsh was: <em>AB =
 0.0058(height)(density)</em> For all equations,
 height was measured in cm, density in stems m<sup>-2</sup>,
 and biomass in g m<sup>-2</sup>.
 <em>Environmental factors </em>
 Elevation (NAVD88) was measured at each plot using Leica Real
 Time Kinematic GS14. Three elevations were taken at each plot and then
 averaged to estimate the elevation. Horizontal and vertical accuracies of
 the measurements were 1 and 2 cm, respectively.
 Sediment cores (7 cm diameter by 20 cm depth) were collected from
 each plot by hand in May 2017 using a plastic core barrel. Two depth
 intervals of 0-10 and 10-20 cm were sectioned and analyzed for bulk
 density, soil organic matter content via loss on ignition (LOI), and soil
 nitrogen availability.  Soil bulk density was measured for each depth
 section by drying to a constant weight at 60°C and dividing by the
 volume.  A 1-g portion of the dried subsample was then combusted in a
 muffle furnace at 550°C for four hours. Soil organic matter was calculated
 by the proportion of sample lost on ignition. Two
 measures of sediment nitrogen availability were made. Extractable ammonium
 (NH<sub>4</sub><sup>+</sup>) was used to indicate
 the availability of nitrogen for primary producers in marsh sediment
 measured as mg N kg<sup>-1</sup> and potentially mineralizable
 nitrogen (PMN) was used to measure of the rate at which extractable
 NH<sub>4</sub><sup>+</sup> increases with time in
 the sediment as an indicator of microbial-mediated ammonification (White
 and Reddy, 2000). For extractable
 NH<sub>4</sub><sup>+</sup><sub>,</sub>
 5 g of homogenized sediment sample from each depth section of each core
 was placed into a 50-ml centrifuge tube with 20 ml of 2
 <em>M</em> L<sup>-1</sup> KCL. Tubes were placed
 into a horizontal shaker for one hour and then centrifuged at 5000 g for
 10 minutes. Samples were filtered through 0.45 um glass fiber filters into
 scintillation vials and preserved with
 H<sub>2</sub>SO<sub>4</sub>.  Extractable
 NH<sub>4</sub><sup>+</sup> was determined using an
 AQ2 Automated Discrete Analyzer (Seal Analytical Inc.) via colorimetric
 analysis. PMN was determined by measuring extractable
 NH<sub>4</sub><sup>+ </sup>at days 0, 2, 5, and 10
 of incubation under anerobic conditions. Day 0 was determined from initial
 extractable NH<sub>4</sub><sup>+
 </sup>concentrations from the soil samples. Three subsamples of each
 soil sample were homogenized,placed into glass serum bottles, which were
 evacuated and replaced with 99.99% N<sub>2</sub>. The bottles
 were then injected with 20 ml of 10 psu salinity water purged by
 N<sub>2</sub> gas and placed into an incubator (IS-971R, Jeio
 Tech) at 40°C, continually oscillating at 100 rpm. The replicate serum
 bottles were removed at day 2, 5, and 10 and extracted with 25 ml of 2
 <em>M</em> L<sup>-1</sup> KCl. Vials were placed
 into a horizontal shaker for one hour and then centrifuged at 5000 g for
 10 minutes. Samples were filtered through 0.45-um membrane filters into 20
 ml scintillation vials and preserved with concentrated sulfuric acid to a
 pH &lt; 2. Extractable
 NH<sub>4</sub><sup>+</sup> was determined using an
 AQ2 Automated Discrete Analyzer (Seal Analytical Inc.) for colorimetric
 analysis of the samples (USEPA, 1993). PMN was determined for each sample
 using linear regression of extractable
 NH<sub>4</sub><sup>+</sup> vs time.
description: # Data from: CO2 fluxes in created and natural marshes in Sabine National
 Wildlife Refuge, Louisiana
 [https://doi.org/10.5061/dryad.xsj3tx9qt](https://doi.org/10.5061/dryad.xsj3tx9qt) ## Description of the data and file structure README Reference Information Provenance for this README *File Name: README_Dataset-CO2 fluxes in created and natural marshes in Sabine National Wildlife Refuge, Louisiana.txt *Authors: Tracy Quirk *Other contributors: Andy Muench, John White, Ron DeLaune *Date Created:2024-09-20 Dataset Version and Release History \* Current Version: \* Number: 1.0.0 \* Date: 2024-09-20 \* Persistent identifier: \* Summary of changes: n/a \* Embargo Provenance: n/a \* Scope of embargo: n/a \* Embargo period: n/a Dataset Attribution and Usage \* Dataset Title: "CO2 fluxes in created and natural marshes in Sabine National Wildlife Refuge, Louisiana" \* Dataset Contributors: \* Creators: Tracy Quirk, Andy Muench, John White and Ron DeLaune \* Date of Issue: 2024-08-21 \* Publisher: Louisiana State University \* License: Use of these data is covered by the following license: \* Title: CC0 1.0 Universal (CC0 1.0) \* Specification: [https://creativecommons.org/publicdomain/zero/1.0/](https://creativecommons.org/publicdomain/zero/1.0/); the authors respectfully request to be contacted by researchers interested in the re-use of these data so that the possibility of collaboration can be discussed. \* Suggested Citations: Dataset citation: ``` \&gt; Quirk, T. et al. 2024. "Dataset: CO2 fluxes in created and natural marshes in Sabine National Wildlife Refuge, Louisiana", Dryad, ``` Contact Information \* Name: Tracy Quirk \* Affiliations: Department of Oceanography and Coastal Sciences, Louisiana State University \* ORCID ID: [https://orcid.org/0000-0002-2068-592X](https://orcid.org/0000-0002-2068-592X) \* Email: [tquirk@lsu.edu](mailto:tquirk@lsu.edu) \* Address: e-mail preferred Additional Dataset Metadata Acknowledgements \* Funding sources: NOAA-Louisiana Sea Grant #: NA140AR4170099 Dates and Locations \* Dates of field sampling: May, July, and September 2017 \* Geographic location: Sabine National Wildlife Refuge, Calcasieu, Louisiana Methodological Information \* Experimental Design:  Ten plots were established in two marshes in the Chenier Plain Region, southwest Louisiana in Sabine National Wildlife Refuge, Hackberry, Louisiana. The marshes were brackish marshes: one was created using dredge sediment in 2015 and was largely unvegetated at the time of the study in 2017 but had sparse clones of *Spartina alterniflora* that were naturally colonizing and spreading and the other marsh was a natural reference marsh dominated by *Spartina alterniflora* and *Spartina patens* along with some other species. Five plots were established in unvegetated areas and five plots in Spartina alterniflora areas of the created marsh and five plots each in Spartina alterniflora and Spartina patens in the natural reference marsh for measurement of carbon dioxide (CO2) fluxes to calculate gross ecosystem productivity (GEP; gross uptake of CO2 by plants and algae), ecosystem respiration (ER; CO2 respiration from primary producers and heterotrophs including microbial decomposers), and net ecosystem exchange (NEE; a measure of the net sink or source of CO2 based on the net of uptake through photosynthesis and losses through respiration). Chambers were established in all plots and CO2 fluxes were measured in May, July and September 2017 within clear chambers for NEE and opaque chambers for ER. Plant biomass, plot elevation, soil nitrogen availability and soil organic matter content and bulk density were also collected to examine relationships to carbon fluxes.  Two measures of soil nitrogen were used: extractable ammonium and potentially mineralizable nitrogen.  ``` \- Marsh type: Natural Reference and Created \- Habitat: Natural Reference: Spartina alterniflora and Spartina patens; Created: unvegetated and Spartina alterniflora (n = 5) \- Month: May, July and September ``` Data and File Overview Summary Metrics \* File count: 1 \* Total file size: 13 KB \* File formats: .csv File Details Details: CO2 fluxes_TQ.csv \* Description: a comma-delimited file containing temperature, photosynthetically active radiation, Gross Ecosystem Productvity (GEP), Ecosystem Respiration (ER), Net Ecosystem Exchange (NEE), marsh elevation, plant biomass, sediment chlorophyll a, extractable ammonium (NH4+) and potential mineralizable nitrogen (PMN), soil organic matter content (%) and soil bulk density for two soil depths (0 - 10 cm and 10 - 20 cm). \* Format(s): .csv \* Size(s): 16 KB \* Dimensions: 61 rows X 21 columns \* Variables: ``` \* Marsh Type: Created or Natural \* Veg: Bare (unvegetated), Salt (Spartina alterniflora), Spat (Spartina patens) \* Treatment: CB (created bare), CS (created Salt), NSa (natural Salt), NSp (natural Spat) \* Plot #: 1 - 10 \* TEMP: average temperature in celsius in chamber \* AVG PAR: average PAR (photosynthetically active radiation) in chamber \* GEP (umol s-1 m-2): Gross Ecosystem Productivity (positive = C-uptake) \* ER (umol s-1 m-2): Ecosystem Respiration \* Elevation (m, NAVD88): marsh elevation in meters relative to the datum North American Vertical Datum 1988 \* NEE (umol s-1 m-2): Net Ecosystem Exchange (balance of GEP and ER) \* Sed chl a (mg/kg soil): sediment chloropyll a concentration \* Plant biomass (g/m2):aboveground biomass \* Soil org matter (%) 0 - 10 cm:percent soil organic matter in 0 - 10 cm depth \* Soil org matter (%) 10 - 20 cm:percent soil organic matter in 10 - 20 cm depth \* Soil bulk density (g cm-3) 0 - 10 cm: soil bulk density in 0 - 10 cm depth \* Soil bulk density (g cm-3) 10 - 20 cm:soil bulk density in 0 - 10 cm depth \* NH4 0 -10 cm (ug cm-3):extractable ammonium (NH4+) in 0 - 10 cm depth \* NH4 10 - 20 cm (ug cm-3):extractable ammonium (NH4+) in 10 - 20 cm depth \* PMN 0 -10 cm (ug cm-3 d-1): potential mineralizable nitrogen in 0 - 10 cm depth \* PMN 10 - 20 cm (ug cm-3 d-1):potential mineralizable nitrogen in 10 - 20 cm depth ``` \* Missing data codes: blank cell END OF README ### Files and variables #### File: CO2\_fluxes\_TQ.csv **Description:**  ##### Variables * \* Marsh Type: Created or Natural \* Veg: Bare (unvegetated), Salt (Spartina alterniflora), Spat (Spartina patens) \* Treatment: CB (created bare), CS (created Salt), NSa (natural Salt), NSp (natural Spat) \* Plot #: 1 - 10 \* TEMP: average temperature in celsius in chamber \* AVG PAR: average PAR (photosynthetically active radiation) in chamber \* GEP (umol s-1 m-2): Gross Ecosystem Productivity (positive = C-uptake) \* ER (umol s-1 m-2): Ecosystem Respiration \* Elevation (m, NAVD88): marsh elevation in meters relative to the datum North American Vertical Datum 1988 * *NEE (umol s-1 m-2): Net Ecosystem Exchange (balance of GEP and ER) * \* Sed chl a (mg/kg soil): sediment chloropyll a concentration \* Plant biomass (g/m2):aboveground biomass \* Soil org matter (%) 0 - 10 cm:percent soil organic matter in 0 - 10 cm depth \* Soil org matter (%) 10 - 20 cm:percent soil organic matter in 10 - 20 cm depth \* Soil bulk density (g cm-3) 0 - 10 cm: soil bulk density in 0 - 10 cm depth \* Soil bulk density (g cm-3) 10 - 20 cm:soil bulk density in 0 - 10 cm depth \* NH4 0 -10 cm (ug cm-3):extractable ammonium (NH4+) in 0 - 10 cm depth \* NH4 10 - 20 cm (ug cm-3):extractable ammonium (NH4+) in 10 - 20 cm depth \* PMN 0 -10 cm (ug cm-3 d-1): potential mineralizable nitrogen in 0 - 10 cm depth \* PMN 10 - 20 cm (ug cm-3 d-1):potential mineralizable nitrogen in 10 - 20 cm depth