Abstract:
This dataset reports carbon content (as % of total weight), the stable isotopic carbon delta-13 composition and radiocarbon-14 values of the marine snow collected as the sediment of mesocosm tanks. Data were collected for four treatments: control (coastal seawater without the addition of oil or dispersants), WAF (water accommodated fraction), CEWAF (Corexit-enhanced WAF), DCEWAF (dilute CEWAF). This dataset also reports the oil concentration (EOE, estimated oil equivalency) measured in COAST for the three treatments that contain amended oil: WAF, CEWAF and DCEWAF. The dissolved organic carbon concentrations of three fractions from the water column for each treatment are included. The fractions are the permeate (< 3 kDa), colloid (3 kDa- 0.45 µm) and filtrate (< 0.45 µm).
Suggested Citation:
Chen Xu, Saijin Zhang, Morgan Beaver, Peng Lin, Luni Sun, Kathy Schwehr, Oscar Agueda, Peter Santschi, Terry Wade, Tony Knapp, Antonietta Quig, Wassim Obieda, Andrew Wozniak, Pat Hatcher. 2017. The carbon budget for microbial EPS production in response to oil and Corexit for COAST, a mesocosm of coastal water with COASTal microbial concentrate. Distributed by: GRIIDC, Harte Research Institute, Texas A&M University–Corpus Christi. doi:10.7266/N7SF2T7V
Purpose:
The carbon content, isotopic composition of carbon, radiocarbon and the estimated oil equivalency (EOE), were used to calculate the sinking carbon to the total carbon, compare the carbon sinking efficiency between different treatments. Also, these data were used to compare the oil removal efficiency when dispersant is absent vs. present. The DOC, dissolved organic carbon, was used to help calculate the carbon distribution in the aqueous phase, and between different treatments.
Data Parameters and Units:
In the DOC dataset, the Colloidal data represents the size fraction between 0.45 micron and 3 kDa, filtrate is < 0.45 micron, and the permeate is < 3 kDa. The experiment had triplicate mesocosms for each treatment, represented here as a, b, c. The placeholder, -0.999, is used to represent when no data is available. In the EOE dataset, the time is given in hours, and all EOE and standard deviation are given in mg/L. For the marine snow carbon data, spreadsheet column headers included are the date that the data was analyzed at the NOSAMS (National Ocean Science Accelerator Mass Spectrometer) facility, the time of sample collection after the experiment began in hours, the treatment, the sample type, the process was run only on organic carbon, accession # is the sample identification for the AMS facility, F Modern is the fraction modern (The Fraction Modern reported requires no further correction for fractionation. Stable isotope delta 13C results reported should not be used to post-correct.), F Modern error is the error for the F Modern, the age and the age error are reported in years, stable isotopic delta 13C is in per mille, D14C is in per mille, and the organic carbon and its error are in % weight. All radiocarbon results were corrected for isotopic fractionation using unreported d13C values measured on the accelerator.
Methods:
Carbon contents were determined with a Perkin-Elmer CHNS 2400 analyzer. Acetanilide (70.09% C, 6.71% H, 10.36 %N) was used as analytical standard. The calibration was checked with Standard Reference Material 1941b and the error was well within 5% of the reported value (Xu et al., 2011). For C-14 and delta C13 determination, samples were sent to National Ocean Sciences Accelerator Mass Spectrometry (NOSAMS). For dissolved organic carbon measurement, samples were measured with a Shimadzu TOC-L analyzer (Xu et al., 2011). For EOE, analysis were run on a UV-Vis spectrophotometer as a dilution in DMSO (Dimethyl sulfoxide) and was calibrated against know concentrations of oil also in DMSO. References: Xu, C.; Zhang, S. J.; Chuang, C. Y.; Miller, E. J.; Schwehr, K. A.; Santschi, P. H., Chemical composition and relative hydrophobicity of microbial exopolymeric substances (EPS) isolated by anion exchange chromatography and their actinide-binding affinities. Marine Chemistry 2011, 126, (1-4), 27-36. Mesocosm methods – COASTal water with coastal microbial concentrate, COAST Twelve 100L mesocosm tanks were filled with Gulf of Mexico seawater collected 5 miles off shore from Galveston (TX) that had been pre-treated with a charcoal filter to remove large particles and debris. Plankton (<63 µm) were collected using a net and transferred into polycarbonate bottles. This concentrated plankton mass was introduced to the tanks (2 L to each final volume 83 L) immediately prior to starting the experiments. Four treatments were prepared in triplicate. Control tanks were filled with seawater and plankton mixture. Water accommodated fraction (WAF) of oil was prepared by mixing 25 mL (5 ml ~ every 30 min for 2.5 hrs) of Macondo surrogate oil into 130 L of seawater then mixing for 12 to 24 hrs. (Knap et al. 1986; Knap et al. 2016 in preparation). The WAF was then introduced into the WAF mesocosm tanks and filled to 87 L and mixed. From these WAF tanks 6 L was removed for other experiments and analyses (2L for roller tables, 2 L dark/light, 4 L hydrocarbon analyses). In order to make chemically enhanced water accommodated fraction (CEWAF), Corexit was mixed with oil in a ratio of 1:20 and 25 mL of this mixture (5 ml every 30 min for 2.5 hrs) of surrogate oil plus Corexit was added to 130 L of seawater which was mixed for 8 to 24 hrs prior to being loaded into the mesocosm tanks. The CEWAF was then introduced into the CEWAF mesocosm tanks and filled to 96 L and mixed. From these CEWAF tanks 15 L was removed for other experiments and analyses (9 L for the DCEWAF mesocosms, 2L for roller tables, 2 L dark/light, 4 L hydrocarbon analyses). Diluted CEWAF (DCEWAF) was prepared by mixing 9 L of CEWAF with 78 L of the original seawater for a total volume of 87 L. From these DCEWAF tanks 6 L was removed for other experiments and analyses (2L for roller tables, 2 L dark/light, 4 L hydrocarbon analyses). The estimated oil equivalents (EOE) were determined using Macondo surrogate oil as the calibration standard (Wade et al. 2011) for the fluorescence analyses (Horiba Scientific Aqualog Fluorometer). The EOE mean concentration of the three mesocosms for the control, WAF, DCEWAF and CEWAF at the start of the experiments were 0 mg/L, 0.26 mg/L, 2.74 mg/L and 41.5 mg/L, respectively. The EOE mean concentration of the three mesocosms for the in the control, WAF, DCEWAF and CEWAF after 72 hours were 0 mg/L , 0.06 mg/L, 1.03. and 17.3 mg/L, respectively. Knap, A. H., T. D. Sleeter, R. E. Dodge, S. C. Wyers, H. R. Frith, and S. R. Smith. 1983. The effects of oil spills and dispersants use on corals: A review and multidisciplinary experimental approach. Oil and Petrochemical Pollution 1: 157–169. Wade, T.L., Sweet S.T., Sericano, J.L., N.L. Guinasso Jr., Diercks, A.-R., Highsmith, R.C., Asper, V.L., Joung, D., Shiller, A.M., Lohrenz, S.E. and Joye, S.B. 2011, Analyses of Water Samples from the Deepwater Horizon Oil Spill: Documentation of the Sub-Surface Plume. in Monitoring and Modeling the Deepwater Horizon Oil Spill: A Record-Breaking Enterprise, Geophysical Monograph Series, vol. 195, edited by Y. Liu et al., pp. 77–82, AGU, Washington, D. C., doi:10.1029/2011GM001103
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