Abstract:

In laboratory experiments, we simulated environmental conditions comparable to surface seawater during Deepwater Horizon (DWH) discharge. The samples collected from surface seawater within an oil slick in the Gulf of Mexico was used in two incubation experiments with water accommodated fractions (WAFs) and chemically enhanced WAFs (CEWAFs). Samples for experiment 1 and experiment 2 were collected in April 2014 and December 2014, respectively. The incubations started within a 5 weeks of initial sample collection. For cell counting, microbial cells were enumerated using epifluorescence microscopy, using SYBR Gold (Invitrogen) stained for 10 minutes and counted at 100x on a Zeiss epifluorescence microscope. The dataset includes mean nutrients, cell counts, bacterial production, model hydrocarbon turnover times, transparent exopolymeric particle (TEP) concentrations of 3 replicates in each of 6 treatments over a period of 4 weeks. Results are reported at Day 0, Day 7, Day 14, and Day 26.

Suggested Citation:

Matt Saxton. 2019. Geochemistry data and biogeochemical rate transformations from 2 incubation experiments using water collected from surface of Gulf of Mexico. Distributed by: GRIIDC, Harte Research Institute, Texas A&M University–Corpus Christi. doi:10.7266/n7-71j6-b618

Purpose:

To investigate the impact of dispersant application on the structure of the microbial assemblage and rates of microbial oil degradation in a natural surface water community.

Data Parameters and Units:

Treatment; Day from Start (d); pH (NBS (National Bureau of Standards)-calibrated); NH4 (umol L-1); NOx (umol L-1); NO2 (umol L-1); PO4 (umol L-1); total dissolved nitrogen (TDN, umol L-1); dissolved organic carbon (DOC, umol L-1); particulate organic carbon (POC, umol L-1); particulate nitrogen (PN, umol L-1); cell densities (cell mL-1); leucine incorporation (% turnover hr-1); naphthalene turnover (% turnover d-1); hexadecane (% turnover d-1); transparent exopolymeric particles (TEPs, Gx eq L-1); KillControl (filtered and pasteurized control); Biotic (biotic control); DispControl (Dispersant only treatment); Oil-WAF (oil water accommodated fraction treatment); Oil-WAF + Nutz (oil water accommodated fraction plus nutrient cocktail treatment); Disp-Oil-WAF (chemically-dispersed-oil water accommodated fraction treatment); Disp-Oil-WAF + Nutz (Chemically-dispersed-oil water accommodated fraction plus nutrient cocktail treatment) All means in this dataset are calculated from triplicate incubations.

Methods:

Water samples for experiment 1 and experiment 2 were collected during the R/V Pelican cruise PE15-08 and the R/V Atlantis cruise AT26-13 at GC600 in the Gulf of Mexico in April 2014 and December 2014, respectively. Incubations started within a 5 weeks of initial sample collection. Oil or oil plus dispersant were added as water accommodated fractions (WAFs) and chemically-enhanced WAFs (CEWAFs), constructed in 2 L bottles using Macondo surrogate oil and Corexit. Nutrients (10 µM potassium nitrate, 1.0 µM potassium phosphate, and either 5 µM (“experiment 1”) or 10 µM (“experiment 2”) were added to half of the treatments, and killed (0.2 µm filtered and twice pasteurized for 2hr at 80ºC) controls, biotic (unamended) controls, and dispersant only controls were additionally followed. Each treatment and control were made in triplicate for each time point. Treatment and control bottles were incubated in the dark at in situ temperature on a roller table. At each time, bottles were destructively sampled for geochemistry, rate transformations, and microbial community structure. Methods for NH4, NOx, PO4, TDN, DOC, naphthalene, hexadecane, and leucine, analysis are described in Kleindienst et al., (2015). Microbial cells were enumerated using epifluorescence microscopy, using SYBR Gold (Invitrogen) stained for 10 minutes and counted at 100x on a Zeiss epifluorescence microscope. A minimum of 400 cells were counted per sample.

Provenance and Historical References:

Kleindienst S, Seidel, M., Ziervogel, K., Grim, S., Loftis, K., Harrison, S., Malkin, S.Y., Perkins, M.J., et al., 2015. Chemical dispersants can suppress the activity of natural oil-degrading microorganisms. Proc. Nat. Acad. Sci. USA 112, 14900–14905. doi/10.1073/pnas.1507380112

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