Barataria Bay carbon mineralization and biogeochemical properties from nine soil cores on 2019-09-05 (NCEI Accession 0291996)

Acquisition Description:
Moisture Content:
Drying a subsample of soil using a gravimetric oven at 70 °C after 3 days or until a constant weight was achieved. Dried soils were ground using a SPEX Sample Prep 8000M Mixer/Mill (Metuchen, NJ).

Bulk Density:
Drying a subsample of soil using a gravimetric oven at 70 °C after 3 days or until a constant weight was achieved. Dried soils were ground using a SPEX Sample Prep 8000M Mixer/Mill (Metuchen, NJ).

pH:
Soil pH was determined by creating a 1:5 slurry of soil to distilled, deionized water, and sub- sequent measurement using an Accument bench top pH probe (Accumet XL200, ThermoFisher Scientific, Waltham, MA, USA).

Total Carbon:
Total Carbon content was determined by use of a Vario Micro Cube CHNS Analyzer on dried, ground subsamples.

Total Nitrogen:
Total Nitrogen content was determined by use of a Vario Micro Cube CHNS Analyzer on dried, ground subsamples.

Total Phosphorus:
Dried, ground sub- samples were used to determine percent organic matter using the loss- on-ignition method, where soils were burned at 550°C in a muffle furnace for a total of 3 h, then soils were digested with 50 mL of 1 N HCl at 100 °C for 30 min, and filtered through Whatman #41 filter paper for total P analysis (Andersen, 1976). Total P content was then determined colorimetrically via an AQ2 Automated Discrete Analyzer (Seal Analytical, Mequon, WI) in accordance with EPA method 365.1 Rev. 2.

Organic Matter Content:
Dried, ground sub- samples were used to determine percent organic matter using the loss- on-ignition method, where soils were burned at 550°C in a muffle furnace for a total of 3 h.

Extractable Dissolved Organic Carbon:
1 g dry weight of field-moist soil were weighed into 40 mL centrifuge tubes and extracted with 25 mL of 0.5 M K2SO4, placed in an orbital shaker for 1 h at 25 °C and 150 rpm then immediately centrifuged for 10 min at 10 °C and 5000 rpm. The supernatant was vacuum filtered through Supor 0.45 μM filters, acidified with double distilled H2SO4 for preservation, and stored at 4 °C until analysis. Dissolved organic carbon (DOC) was determined by use of a Shimadzu TOC-L Analyzer (Kyoto, Japan).

Extractable Nitrate:
2.5 g of wet soil (both from the field and from the bottle incubation) into 40 mL centrifuge tubes and adding 25 mL of 2 M KCl. Samples were then shaken continuously on an orbital shaker for 1 h at 25 °C and 150 rpm, then centrifuged for 10 min at 10 °C and 5000 rpm. Following the centrifuge, samples were immediately filtered through Supor 0.45 μM filters and acidified with double distilled H2SO4 to a pH of < 2 for preservation. Extractable nutrients samples were then analyzed using an AQ2 Automated Discrete Analyzer (Seal Analytical, Mequon, WI, EPA methods 231-A Rev.0, 210-A Rev.1, and 204-A Rev.0).

Extractable Ammonium:
2.5 g of wet soil (both from the field and from the bottle incubation) into 40 mL centrifuge tubes and adding 25 mL of 2 M KCl. Samples were then shaken continuously on an orbital shaker for 1 h at 25 °C and 150 rpm, then centrifuged for 10 min at 10 °C and 5000 rpm. Following the centrifuge, samples were immediately filtered through Supor 0.45 μM filters and acidified with double distilled H2SO4 to a pH of < 2 for preservation. Extractable nutrients samples were then analyzed using an AQ2 Automated Discrete Analyzer (Seal Analytical, Mequon, WI, EPA methods 231-A Rev.0, 210-A Rev.1, and 204-A Rev.0).

Extractable Soluble Reactive Phosphorus:
2.5 g of wet soil (both from the field and from the bottle incubation) into 40 mL centrifuge tubes and adding 25 mL of 2 M KCl. Samples were then shaken continuously on an orbital shaker for 1 h at 25 °C and 150 rpm, then centrifuged for 10 min at 10 °C and 5000 rpm. Following the centrifuge, samples were immediately filtered through Supor 0.45 μM filters and acidified with double distilled H2SO4 to a pH of < 2 for preservation. Extractable nutrients samples were then analyzed using an AQ2 Automated Discrete Analyzer (Seal Analytical, Mequon, WI, EPA methods 231-A Rev.0, 210-A Rev.1, and 204-A Rev.0).

Microbial Biomass Carbon:
Microbial biomass C (MBC) was determined on soils both immediately after the field sampling and soils from the bottles after the incubation period following the method outlined in Vance et al. (1987). Duplicates of approximately 1 g dry weight of field-moist soil were weighed into 40 mL centrifuge tubes and assigned to either a fumigate or non-fumigate treatment. The fumigated samples were exposed to gaseous chloroform for 24 h in a glass desiccator. After 24 h, the sam- ples were extracted with 25 mL of 0.5 M K2SO4, placed in an orbital shaker for 1 h at 25 °C and 150 rpm. After incubation, samples were immediately centrifuged for 10 min at 10 °C and 5000 rpm. The supernatant was vacuum filtered through Supor 0.45 μM filters, acidified with double distilled H2SO4 for preservation, and stored at 4 °C until analysis. Non-fumigate samples were processed in the same manner, excluding the chloroform fumigation. Dissolved organic carbon (DOC) was determined by use of a Shimadzu TOC-L Analyzer (Kyoto, Japan). Microbial biomass C was calculated as the difference between the fumigated samples and the non-fumigated samples.

B-glucosidase activity:
Assays were conducted using fluorescent substrate 4‐ methylumbelliferone (MUF) for standardization and fluorescently labeled MUF-specific sub- strates (German et al., 2011). To create a 1:100 slurry, 0.5 g of soil was added to 39 mL of autoclaved distilled deionized water and shaken continuously on an orbital shaker for 1 h at 25 °C and 150 rpm. Fluor- escence was measured at excitation/emission wavelengths 360/460 on a BioTek Synergy HTX (BioTek Instruments, Inc., Winooski, VT, USA) both immediately after substrate and sample were added, and 24 h later to determine a rate of enzyme activity.

N‐acetyl‐beta‐D‐glucosaminidase activity:
Assays were conducted using fluorescent substrate 4‐ methylumbelliferone (MUF) for standardization and fluorescently labeled MUF-specific sub- strates (German et al., 2011). To create a 1:100 slurry, 0.5 g of soil was added to 39 mL of autoclaved distilled deionized water and shaken continuously on an orbital shaker for 1 h at 25 °C and 150 rpm. Fluor- escence was measured at excitation/emission wavelengths 360/460 on a BioTek Synergy HTX (BioTek Instruments, Inc., Winooski, VT, USA) both immediately after substrate and sample were added, and 24 h later to determine a rate of enzyme activity.

Alkaline phosphatase activity:
Assays were conducted using fluorescent substrate 4‐ methylumbelliferone (MUF) for standardization and fluorescently labeled MUF-specific sub- strates (German et al., 2011). To create a 1:100 slurry, 0.5 g of soil was added to 39 mL of autoclaved distilled deionized water and shaken continuously on an orbital shaker for 1 h at 25 °C and 150 rpm. Fluor- escence was measured at excitation/emission wavelengths 360/460 on a BioTek Synergy HTX (BioTek Instruments, Inc., Winooski, VT, USA) both immediately after substrate and sample were added, and 24 h later to determine a rate of enzyme activity.

Xylosidase activity:
Assays were conducted using fluorescent substrate 4‐ methylumbelliferone (MUF) for standardization and fluorescently labeled MUF-specific sub- strates (German et al., 2011). To create a 1:100 slurry, 0.5 g of soil was added to 39 mL of autoclaved distilled deionized water and shaken continuously on an orbital shaker for 1 h at 25 °C and 150 rpm. Fluor- escence was measured at excitation/emission wavelengths 360/460 on a BioTek Synergy HTX (BioTek Instruments, Inc., Winooski, VT, USA) both immediately after substrate and sample were added, and 24 h later to determine a rate of enzyme activity.

Cellobiosidase activity:
Assays were conducted using fluorescent substrate 4‐ methylumbelliferone (MUF) for standardization and fluorescently labeled MUF-specific sub- strates (German et al., 2011). To create a 1:100 slurry, 0.5 g of soil was added to 39 mL of autoclaved distilled deionized water and shaken continuously on an orbital shaker for 1 h at 25 °C and 150 rpm. Fluor- escence was measured at excitation/emission wavelengths 360/460 on a BioTek Synergy HTX (BioTek Instruments, Inc., Winooski, VT, USA) both immediately after substrate and sample were added, and 24 h later to determine a rate of enzyme activity.

Rate of carbon dioxide production (potential):
Duplicate subsamples (approximately 7 g) from each depth segment of each core were weighed into 100 mL glass serum bottles, capped with a rubber septa and aluminum crimp and evacuated to −75 mm Hg. Replicate bottles were randomly assigned to one of two treatments: anaerobic (purged with 99% O2-free N2 gas for 3 min), or aerobic (purged with Breathing Grade air containing 21% O2 for 3 min). Anaerobic bottles were injected with 14 mL of filtered, N2-purged site water, while aerobic bottles were injected with 14 mL of filtered, breathing air-purged site water. Bottles were then placed on an orbital shaker at 150 rpm and 25 °C. Headspace samples were taken at 1, 2, 4, 7, 10, and 14 day time points, and injected into a GC-2014 gas chromatograph (Shimadzu Instrument, Kyoto, Japan) equipped with a flame ionization detector. Respiration rates were calculated as the change in CO2 production over time. After each gas sample was extracted from the bottles' headspace, the bottle was purged with either 99% O2- free N2 gas or Breathing Grade air for 3 min, depending on treatment.

Rate of nitrate mineralization (potential):
Following the 14 day incubation, bottles were uncapped, and the remaining soil sample was placed in a 20 mL HDPE scintillation vials

Rate of ammonium mineralization (potential):
for analysis of extractable ammonium (NH4+), nitrate (NO3−), and soluble reactive phosphorus (SRP), microbial biomass C, and enzyme analysis.