Delta-X: Feldspar Sediment Accretion Measurements for Coastal Wetlands, MRD, LA, USA

This dataset is from the Delta-X campaign that was conducted during Fall 2020 and Spring 2021. Feldspar Stations were established nearby Louisiana's Coastwide Reference Monitoring Systems (CRMS) sites and on Mike Island in Wax Lake Delta (WLD) to capture recent sediment deposition rates across hydrogeomorphic zones defined as discrete surface elevation ranges relative to NAVD88 (e.g., subtidal < -0.04 m, intertidal -0.04 m to 0.30 m, and supratidal > 0.30 m; after Bevington & Twilley 2018). Hydrogeomorphic zones classification was based on marsh surface elevation measurements acquired in November and December 2020 using a RTK GPS (Trible R12, using Geoid 18). Between two and four feldspar stations were deployed approximately 25 and 50 meters from a main channel to represent existing hydrogeomorphic zones in brackish and saline emergent marsh vegetation, brackish and saline ponds within emergent marshes, tidal freshwater emergent marshes, and forested swamps. Cryocore technique was used to determine recent sediment deposition. Soil samples were collected to determine organic and inorganic fractions and organic carbon content.

This dataset includes 1 file in comma-separated values (*.csv) format. 

The QA and documentation of this dataset is in progress.

The Delta-X mission is a 5-year NASA Earth Venture Suborbital-3 mission to study the Mississippi River Delta in the United States, which is growing and sinking in different areas. River deltas and their wetlands are drowning as a result of sea level rise and reduced sediment inputs. The Delta-X mission will determine which parts will survive and continue to grow, and which parts will be lost. Delta-X begins with airborne and in situ data acquisition and carries through data analysis, model integration, and validation to predict the extent and spatial patterns of future deltaic land loss or gain.

The dataset represents one-time field measurements taken during the Fall 2020 and Spring 2021 field campaigns.

Parameters or variables provided in the dataset

Variable	Unit of measurement	Description	Collected during Delta-X campaign?
basin	N/A	Atchafalaya or Terrebonne Basin	YES
campaign	N/A	Fall 2020 or Spring 2021 feldspar sampling campaign	YES
site_id	N/A	Site ID’s: CRMS_0294, CRMS_0322, CRMS_0399, CRMS_0396, CRMS_0421, CRMS_2568, WLD_T1, WLD_T3.	YES
hydrogeomorphic_zone	N/A	Hydrogeomorphic zone classification: subtidal, intertidal or supratidal	YES
elevation_navd88	meters	Elevation in meters relative to NAVD88	YES
latitude	decimal degrees	Latitude in decimal degrees	YES
longitude	decimal degrees	Longitude in decimal degrees	YES
station	N/A	Feldspar Stations ID’s: herbaceous marshes (V25 and V50), ponds (P25 and P50), forested swamp (T25), Supratidal (SUP) and Subtidal (SUB)	YES
plot	N/A	50 x 50 cm feldspar marker horizons plots: X, Y and Z	YES
replicate	N/A	Replicate ID’s for measurements taken from each cryocore: A,B or C	YES
sample_id	N/A	Unique soil samples ID’s	YES
time_marker_deployed	Year-Month-Day  Hour:minutes:seconds	Date and time feldspar marker horizon plots were deployed	YES
time_marker_sampled	Year-Month-Day  Hour:minutes:seconds	Date and time feldspar marker horizon plots were sampled	YES
sediment_accretion	millimeter	Height of sediment accreted on top of feldspar marker horizon plots since deployment date	YES
days_between_sampling_and_deployment	days	Number of days between feldspar marker horizon plots deployment and sampling event	YES
normalized_accretion	millimeter per year	Yearly normalized sediment accretion (mm yr-1) obtained by multiplying sediment accretion (mm) by 365 days per year and then dividing the result by the number of days between feldspar marker horizon plots deployment and sampling event	YES
soil_bulk_density	grams per cubic centimeter	Soil bulk density calculated from the sample's dry weight divided by its wet volume. Wet volume determined from the cross-sectional area of the core (cm2) multiplied by the length the soil column interval (cm)	YES
soil_organic_matter_content	percentage (% of dry mass)	Organic matter content determined by loss on ignition	YES
soil_organic_carbon	percentage (% of dry mass)	Percent organic carbon determined on acid-fumigated soil samples using elemental analyzer	YES
soil_organic_carbon_density	grams per cubic centimeter	Soil organic density obtained by multiplying sample's bulk density (g cm-3) by its organic carbon fraction (g g-1).	YES

Feldspar data will be used to calibrate and validate the ecogeomorphic (NUMAR, modified from NUMAN model by Chen and Twilley 1998) and hydrodynamic models. Data will be used to characterize in situ sediment deposition patterns across all Delta X sites and to explain changes in sediment deposition across distinct hydrogeomorphic zones. This research will contribute to a better understanding of changes in sediment accretion, organic matter accumulation rates and soil carbon sequestration rates due to vegetation composition, salinity gradients and riverine sediment and nutrient loadings.

Data quality for each loss on ignition and carbon content on soil samples was determined on duplicate analytical replicates of each sample and the run precision was determined based on relative percent difference between replicates at an acceptance limit of <5%. For carbon content, accuracy and quality control were determined by the analysis of certified standard reference material during each run. Acceptable limits for accuracy were ± 5%. Data outside these limits was not used and samples were re-run to obtain new accurate values.

Feldspar Stations were established nearby Louisiana's Coastwide Reference Monitoring Systems (CRMS) sites and on Mike Island in Wax Lake Delta (WLD) to capture recent sediment deposition rates across hydrogeomorphic zones defined as discrete surface elevation ranges relative to NAVD88 (e.g., subtidal < -0.04 m, intertidal -0.04 m to 0.30 m, and supratidal > 0.30 m; after Bevington & Twilley 2018). Hydrogeomorphic zones classification was based on marsh surface elevation measurements acquired in November and December 2020 using a RTK GPS (Trible R12, using Geoid 18). For CRMS_0294 and CRMS_0322, two feldspar stations were deployed in vegetated areas approximately 25 and 50 meters from a main channel (V25 & V50). For CRMS_0399, three feldspar stations were deployed: two feldspar stations were deployed in vegetated areas approximately 25 and 50 meters from a main channel (V25 & V50), and one pond station deployed at the edge of a pond approximately 25 meters from a main channel (P25). For CRMS_0396 and CRMS_0421, four stations were deployed at each site: two feldspar stations were deployed in vegetated areas approximately 25 and 50 meters from a main channel (V25 & V50), and two pond stations deployed at the edge of ponds approximately 25 and 50 meters from a main channel (P25 & P50). For CRMS_2568, two feldspar stations were deployed: one station in herbaceous vegetation (V25) and one station in forested vegetation (T25), both approximately 25 meters from a main channel. In Wax Lake Delta (WLD), six feldspar stations were deployed: three stations along a transect near the island’s apex at supratidal and subtidal (SUP & SUB) hydrogeomorphic zones, and three stations along a transect near delta front at supratidal and subtidal (SUP & SUB) hydrogeomorphic zones. At each feldspar station, three 50 x 50 cm feldspar marker horizons plots (X, Y, and Z) were deployed on the soil surface. Each cryocore sample measured for accretion was given a replicate ID (A,B or C). Each cryocore showing a clear, white feldspar marker horizon was measured from the current soil surface to the top of the feldspar marker horizon. Each accretion measurement reported is the average of three individual measurements made with calipers.

 

Soil cores corresponding to sediment accretion measurements (e.g., height of sediment above feldspar marker) obtained in the cryocores were collected next to feldspar markers horizon plots to account for organic and inorganic fractions of newly deposited material. This strategy allowed for reducing disturbance of feldspar markers horizon plots, extending the makers’ longevity. Soil samples were dried at 60°C until constant weight. Bulk density was calculated as the sample's dry weight divided its wet volume (g cm^-3). Wet volume is determined from the cross-sectional area (cm²) of the soil core multiplied by the depth of each soil section (cm, based on the height of sediment above feldspar marker). Samples were homogenized and ground using a Wiley Mill. Organic matter content was determined by loss on ignition after combusting samples of a known mass at 550°C for 2 hours (Davies, 1974). Soil samples were fumigated in a desiccator for 8 hours with 12M HCl to remove inorganic carbonates (Harris et. al. 2001). Percent organic carbon on fumigated samples was measured with a ECS 4010 elemental analyzer (Costech Analytical Technologies Inc., Valencia, California). Soil organic density was calculated by multiplying the sample's bulk density (g cm-3) by the sample' s organic carbon fraction (g g-1).

Bevington A.E., Twilley R.R (2018) Island Edge Morphodynamics along a Chronosequence in a Prograding Deltaic Floodplain Wetland. Journal of Coastal Research 34(4), 806-817.

Chen, R., & Twilley, R.R. (1999). A simulation model of organic matter and nutrient accumulation in mangrove wetland soils. Biogeochemistry 44, 93–118.

Davies, B. E. (1974). Loss‐on‐ignition as an estimate of soil organic matter. Soil Science Society of America Journal, 38(1), 150-151.

Harris D., Horwáth W.R., van Kessel C. (2001). Acid fumigation of soils to remove carbonates prior to total organic carbon or carbon-13 isotopic analysis. Soil Science Society of America Journal 65. 1853–1856.