Abstract:

We conducted seasonal (March, May, July, September, November 2013 and February, April, July, October 2014) measurements of net soil greenhouse gas (CO2, CH4, and N2O) fluxes at 4 locations (5, 10, 15, and 20m from the marsh edge) in 4 marsh sites in Terrebonne Bay, LA. These sites include paired oiled and unoiled marshes in the Bay LaFleur and northern Lake Barre regions of Terrebonne Bay. Additionally, we measured a series of basic site characterizations (water depth, soil, porewater and overlying water temperature and salinity), soil properties (soil water content, redox, pH, organic C, total N and P, bulk density, extractable inorganic nutrients), and characterized the dissolved inorganic nutrient concentrations in porewater, overlying water and adjacent bay water samples.

Suggested Citation:

Roberts, Brian, and John Marton. 2016. Marsh soil net greenhouse gas fluxes and explanatory variables, Terrebonne Bay (LA), 2013-2014. Distributed by: GRIIDC, Harte Research Institute, Texas A&M University–Corpus Christi. doi:10.7266/N7QJ7F7M

Purpose:

This dataset was developed as part of a research project investigating the effects of the Deepwater Horizon oil spill on salt marsh biogeochemistry. This component of the CWC research effort addressed the following questions: 1) Do greenhouse gas fluxes vary seasonally and/or with marsh position?; 2)What are the primary drivers of net greenhouse gas fluxes?; 3) Are these results different between oiled and unoiled marshes?; and 4) Is there interannual variability in any of these patterns or responses to oiling?

Data Parameters and Units:

Region--region of sample collection (TB=Terrebonne Bay) Site--Site identifier Latititude (decimal degrees) Longitude (decimal degrees) Oil status--Indicates whether the marsh received Macondo Oil (Oiled) or not (Unoiled) Plot--Plot identifier along the sampling transect Distance (m)--Distance from the marsh edge of the sampling plot (meters) Month-Year--Indicates the month and year that samples were collected or measurements made net CO2 flux (micromol/m2/h)--net carbon dioxide (CO2) flux from the soil to the atmosphere net CH4 flux (micromol/m2/h)--net methane (CH4) flux from the soil to the atmosphere net N2O flux (micromol/m2/h)--net nitrous oxide (N2O flux from the soil to the atmosphere Soil T (°C)--soil temperature at the plot soil pH--pH of the top 5 cm of soil at the plot soil Eh--soil redox potential (Eh) in the surface soil of the plot (units = mV) soil bulk density (g/cm3)--bulk density of the top 5 cm of soil at the plot soil organic C (%)--organic carbon content of the top 5 cm of soil at the plot soil total N (%)--total nitrogen content of the top 5 cm of soil at the plot soil total P (micrograms per gram dry mass)--total phosphorus content of the top 5 cm of soil at the plot soil CN (mol:mol)--organic carbon to total nitrogen ratio of the top 5 cm of soil at the plot soil NP (mol:mol)--total nitrogen to total phoshorus ratio of the top 5 cm of soil at the plot soil CP (mol:mol)--organic carbon to total phosphorus ratio of the top 5 cm of soil at the plot soil water content (%)--gravimetric water content of the top 5 cm of soil at the plot soil extractable NO3 (micromol per grams dry weight of soil)--extractable nitrate + nitrite concentration of the top 5 cm of soil at the plot soil extractable NH4 (micromol per grams dry weight of soil)--extractable ammonium concentration of the top 5 cm of soil at the plot soil extractable PO4 (micromol per grams dry weight of soil)--extractable orthophosphate concentration of the top 5 cm of soil at the plot Porewater salinity (psu)--salinity of porewater from the plot Porewater NO3-N + NO2-N (micromols per liter)--nitrate + nitrite concentration of porewater Porewater NH4-N (micromols per liter)--ammonium concentration of porewater Porewater PO4-P (micromols per liter)--orthophosphate concentration of porewater water depth (cm)--depth of overlying water at plot water temp (°C)--temperature of overlying water at plot Salinity (psu)--salinity of overlying water at plot Specific conductance (mS)--specific conductance of overlying water at plot Overlying water NO3-N + NO2-N (micromols per liter)--dissolved nitrate + nitrite concentration of overlying water at plot Overlying water NH4-N (micromols per liter)--dissolved ammonium concentration of overlying water at plot Overlying water PO4-P (micromols per liter)--dissolved orthophosphate concentration of overlying water at plot Overlying water SiO2 (micromols per liter)--dissolved silicate concentration of overlying water at plot water temp (°C)--temperature of baywater adjacent to site Salinity (psu)--salinity of baywater adjacent to site Specific conductance (mS)--specific conductance of baywater adjacent to site Baywater NO3-N + NO2-N (micromols per liter)--dissolved nitrate + nitrite concentration of baywater adjacent to site Baywater NH4-N (micromols per liter)--dissolved ammonium concentration of baywater adjacent to site Baywater PO4-P (micromols per liter)--dissolved orthophosphate concentration of baywater adjacent to site Baywater SiO2 (micromols per liter)--dissolved silicate concentration of baywater adjacent to site

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