Abstract:

Mesocosm experiments were performed with Gulf of Mexico seawater collected from the Flower Gardens National Marine Sanctuary Area (27° 53.4180'N; 94° 2.2020'W) which was amended with nutrients. Four treatments in triplicate were analyzed for oil composition: 1) Control, 2) Water accommodated oil fraction (WAF), 3) Chemically enhanced (Corexit 9500) water accommodated fraction (CEWAF), and 4) 10-fold diluted CEWAF (DCWAF). The oil composition data presented here are EOE (estimated oil equivalence using fluorescence), PAH (polycyclic aromatic hydrocarbons), and Total PAH. Additionally, nutrients for these treatments are also included.

Suggested Citation:

Terry L. Wade, Anthony H. Knap, Dawei Shi, Gerardo Gold-Bouchot, Maya E. Morales-McDevitt, Stephen T. Sweet, Peter H. Santschi and Antonietta Quigg. 2017. Oil Composition and nutrients for the GOMOO mesocosm using Gulf Of Mexico Open Ocean water. Distributed by: Gulf of Mexico Research Initiative Information and Data Cooperative (GRIIDC), Harte Research Institute, Texas A&M University–Corpus Christi. doi:10.7266/N78P5XZD

Publications:

Schwehr, K. A., Xu, C., Chiu, M.-H., Zhang, S., Sun, L., Lin, P., … Santschi, P. H. (2018). Protein: Polysaccharide ratio in exopolymeric substances controlling the surface tension of seawater in the presence or absence of surrogate Macondo oil with and without Corexit. Marine Chemistry, 206, 84–92. doi:10.1016/j.marchem.2018.09.003

Doyle, S. M., Lin, G., Morales-McDevitt, M., Wade, T. L., Quigg, A., & Sylvan, J. B. (2020). Niche Partitioning between Coastal and Offshore Shelf Waters Results in Differential Expression of Alkane and Polycyclic Aromatic Hydrocarbon Catabolic Pathways. mSystems, 5(4). doi:10.1128/msystems.00668-20

Purpose:

To determine the concentration of oil constituents and dispersant and their degradation with time in four different mesocosm treatments from coastal waters. Also, to track the change in nutrients during the same time course.

Data Parameters and Units:

EOE (Estimated Oil Equivalence, mg/L); PAH (Polycyclic Aromatic Hydrocarbons, ng/L); Total PAH (ng/L); WAF (Water Accommodated Fraction); CEWAF (Chemically Enhanced Water Accommodated Fraction); DCEWAF (Diluted Chemically Enhanced Water Accommodated Fraction); nutrient data are given in 2 conc. or concentration formats: micromoles/L (umol/L) and mg/L with respect to the listed standard. NO3- is nitrate, N is nitrogen, HPO4= is hydrogen phosphate, P is Phosphorus, HSIO3- is hydrogen silicate, SiO3 refers to silicate, NH4+ is ammonium, NO2- is nitrite, Urea, Nitrate+Nitrite, Time (hr) intervals were at 0, 24, 48, 72, 96; Volume (L); LB=light bottle; DB=dark bottle; -999 = below detection limit, Individual alkanes (ng/L), Total alkanes (ng/L), Volume (L), Extraction date (MM/DD/YYYY), Analysis date (MM/DD/YYYY HH:MM:SS), Total resolved (ug/L), Total TPH (ug/L), Total UCM (ug/L) Treatments: O = WAF DM = diluted CWAF M = CWAF

Methods:

Twelve 100L mesocosm tanks were filled with Gulf of Mexico seawater collected from the Flower Gardens National Marine Sanctuary Area (27° 53.4180'N; 94° 2.2020'W) which is located ~120 miles off the coast of Galveston (TX). Four treatments were prepared in triplicate. Control tanks were filled with seawater. 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. Mixing ended 24 hrs after the initial oil addition (Knap et al. 1986; Wade et al. 2017 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 (2 L light /dark bottles, 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. Mixing ended 24 hrs after the initial oil addition. The CEWAF was then introduced into the CEWAF mesocosm tanks and filled to 96 L and mixed. From these CEWAF tanks 13 L was removed for other experiments and analyses (7 L for the DCEWAF mesocosms, 2 L light/dark, 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 (2 L light/dark, 4 L hydrocarbon analyses). To the water in the 12 mesocosms, nutrients were added (final concentration f/20) and the tanks stirred. Banks of lights were placed behind each of the glass mesocosm tanks and a 12:12 light/dark cycle employed. Sampling commenced and defined as time zero. 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. Estimated Oil Equivalence (EOE) The estimated oil equivalents (EOE) were determined by fluorescence (Wade et al. 2011) using Macondo surrogate oil as a standard to produce calibration curves at 5 to 7 concentrations. Water samples (5 to 20 ml) were extracted with 5 ml of dichloromethane. An aliquot of the extract was placed in a cuvette for fluorescence analyses (Horiba Scientific Aqualog Fluorometer). The EOE were determined from the calibration curve (Wade et al. 2011). Samples with florescence responses that exceeded the calibration curve were diluted so that their florescence was within the calibration range. Samples were taken at the beginning and end of the experiment and at intervals in between and at the same time point as measurements of other parameters during the experiment. PAH (polycyclic aromatic hydrocarbons) and Total PAH extraction of the sample with dichloromethane. The samples are then purified using silica/alumina columns. analyzed. The analysis is performed with gas chromatography to separate the individual aromatic compounds and with a mass selective detector in the selected ion mode for identification and quantification. The parent PAH (e.g. naphthalene) and its alkylated homolog’s (e.g. C-1, C-2, C-3 and C-4) are also determined. These analyses can be used to distinguish between petroleum and combustion sources or a mixture of these sources. The individual PAH compounds and their alkylated homologs are reported.

Instruments:

EOE fluorescence analyses was carried out using a Horiba Scientific Aqualog Fluorometer. Total PAH were determined by gas chromatography (GC) with a flame ionization detector (GC/FID) and PAHs by GC with a mass selective detector [Short et al., 1996].

Provenance and Historical References:

Short, J. W., T. J. Jackson, M. L. Larsen, and T. L. Wade (1996), Analytical methods used for the analysis of hydrocarbons in crude oil tissues, sediments, and seawater collected for the natural resources damage assessment of the Exxon Valdez oil spill, in Proceedings of the Exxon Valdez Oil Spill Symposium, edited by S. D. Rice et al., pp. 140–148, Am. Fish. Soc., Bethesda, Md. Wade, T. L., S. T. Sweet, J. N. Walpert, J. L. Sericano, J. J. Singer, and N. L. Guinasso Jr. (2011), Evaluation of possible inputs of oil from the Deepwater Horizon spill to the Loop Current and associated eddies in the Gulf of Mexico, in Monitoring and Modeling the Deepwater Horizon Oil Spill: A Record-Breaking Enterprise, Geophys. Monogr. Ser., doi:10.1029/2011GM 001095. 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.

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