Abstract:

The Deepwater Horizon oil spill has contributed to significant loss of marsh vegetation. Decreased marsh vegetation habitats can lead to a reduction in organic carbon and other key nutrients available for microbial communities in sediments. Potential denitrification rates were achieved by collecting 0-2 cm and 5-7 cm sediments in vegetated marsh and unvegetated intertidal marsh habitats. Sediments were treated with and without nitrate and rates will be determined using acetylene inhibition technique.

Suggested Citation:

Mortazavi, Behzad. 2017. Potential denitrification rates in moderately oiled marshes at the Chandeleur Island, July 2015 to February 2016. Distributed by: GRIIDC, Harte Research Institute, Texas A&M University–Corpus Christi. doi:10.7266/N7GX48KH

Publications:

Hinshaw, S. E., Tatariw, C., Flournoy, N., Kleinhuizen, A., Taylor, C., Sobecky, P. A., & Mortazavi, B. (2017). Vegetation Loss Decreases Salt Marsh Denitrification Capacity: Implications for Marsh Erosion. Environmental Science & Technology, 51(15), 8245–8253. doi:10.1021/acs.est.7b00618

Purpose:

The purpose of this study was to measure potential denitrification rates in moderately oiled marsh and intertidal habitats

Data Parameters and Units:

Date: month, day and year, Location A: Location of site on Chandeleur Island map, Habitat: sediments were collected from intertidal habitats or marsh habitats, treatment: control is site water only while nitrate is addition of 100 µM KNO3-, depth: sediments were collected at depths of 0-2 cm and 5-7 cm, replication: number of replicate bottles per sample, denitrification rates: measured in micromoles of nitrogen per meter squared per hour (µmol N m2 hr-1), N2O, Nitrous oxide: measured in micromoles of nitrogen per meter squared per hour (µmol N m2 hr-1), NO3- + NO2, nitrate plus nitrogen dioxide: measured in micromoles per liter of nitrogen (µM N), PO4, phosphate: measured in micromoles per liter of phosphorus (µM), NO2, nitrogen dioxide: measured in micromoles per liter of nitrogen (µM N), NH4+, ammonium: measured in micromoles per liter of ammonium (µM), NO3-, nitrate: measured in micromoles per liter of nitrogen (µM N), DIN, dissolved inorganic nitrogen: measured in micromoles per liter of nitrogen, NPOC, dissolved organic carbon: measured in milligrams per liter (umol C L-1), Moisture: water filled pore space measured in percent of water in sediment, bulk density: measured in grams per centimeter cubed (g cm3) latitude: measured in degrees minutes and seconds, longitude: measured in degrees minutes and seconds.

Methods:

Potential denitrification rates were measured using the acetylene inhibition technique. Sediments were collected from marsh and intertidal habitats at depths of 0-2cm and 5-7cm. Approximately 20 g of sediment and 35 ml of site water was placed in 70ml serum bottles. Twelve bottles were reserved for a control treatment which included site water only, while twelve bottles were amended with 1ml of 100 µM KNO3-. Samples were crimped with a butyl stopper and flushed with N2 gas for 10 minutes. Samples were then injected with acetylene and placed on a shaker table for 1 hour. This process was repeated with a second set of 24 bottles without the addition of acetylene to measure the amount of N2O produced during the denitrification process. After 1 hour, headspace was injected into 12 ml Labco vials and stored at room temperature until analysis the following day. Gas samples were measured with a gas chromatograph equipped with an ECD.

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