Abstract:
Samples were collected from three different origins (two from the subtropical area and one from the Arctic ocean) were used for generating geochemical data, including microbial respiration rates and percentage hydrocarbon degraded during the incubation period. Following the incubation, 16s rRNA library was generated. Experiments were divided into multiple groups, with a systemic combination of different temperature and nutrients addition.
Suggested Citation:
Xiaoxu Sun and Joel Kostka. 2019. Hydrocarbon-degrading microbial communities are site-specific and their activity is limited by synergies in temperature and nutrient availability in surface ocean waters. Distributed by: GRIIDC, Harte Research Institute, Texas A&M University–Corpus Christi. doi:10.7266/n7-df3b-bq71
Purpose:
The objective of this study was to quantify the potential for hydrocarbon biodegradation in surface waters of three sites that represent geographic regions of major oil exploration in a systematic experimental design that incorporates gradients in temperature and the availability of major nutrients.
Data Parameters and Units:
TB_rate_original: calculated respiration rates for each individual microcosm. Sample collection site, incubation temperature (temp; degrees C), microcosm treatment (Nutrient Amended (NA)/Unamended (UN)), maximum CO2 accumulation rate (mu.TB.spline; micromol CO2/day), mu.TB.spline converted to per Liter seawater per day (R; micromol CO2/L seawater/day).
TB_all_rates_avg: averages of the measured respiration rated in replicates. Sample collection site, incubation temperature (temp; degrees C), microcosm treatment (Nutrient Amended (NA)/Unamended (UN)), averaged respiration rates (respiration; micromol CO2/L seawater/day), averaged respiration rates standard deviation (respiration_std), NA/UN (rate increase (ratio) between NA and UN treatment at the same temperature from the same site, averaged respiration rate at maximum (30C for CB2 and 38 for DWH01 and IXTOC01) comparing to that at 4C (Ropt/R4), Ropt/R4 standard deviation (Ropt/R4_STDEV), statistical results (p-value and significance for sample pairs for T-test comparison between sites for Ropt/R4.
Ea: calculation results for activation energies. Sample collection site, microcosm treatment (Nutrient Amended (NA)/Unamended (UN)), mean activation energy calculated based on respiration rates (Mean; kJ/mol), standard deviation of activation energy (Std), calculated Q10 value (rate change when temperature increases 10C) at 20 C (Q10@20C).
qPCR: quantitative PCR results for 16s rRNA, nifH gene, and their ratio. Sample collection site, incubation temperature (temp; degrees C), microcosm treatment (Nutrient Amended (NA)/Unamended (UN)), average abundance of 16s gene copy number (abund_16s; copy of 16s/L of seawater), standard deviation of the abundance of 16s gene copy number (stdev_16s), average abundance of nifH gene copy number (abund_nifH; copy of 16s/L of seawater), standard deviation of the abundance of nifH gene copy number (stdev_nifH), averaged relative abundance of nifH gene in microbial community (nifH/16s, percent), standard deviation of averaged relative abundance of nifH gene in microbial community (stdev_nifH/16s, percent).
Colwellia: the sequence of the most abundant Colwellia strain found in the microcosms. Sequence id (row 1), nucleic acid sequence (row 2), blast result of the most closely related sequences in the NCBI database (rows 4-7).
Sample collection sites: latitude and longitude (decimal degrees), and collection date (mm/dd/yyyy):
Site CB2: 75.470000, 129.17000, 08/03/2015
Site DWH01: 28.430000, -88.230000, 08/20/2015
Site IXTOC01: 19.000000, -92.000000, 08/03/2015
Methods:
For each site, microcosms were constructed by amending 5 ml of seawater with 5 μl of surrogate MC252 oil in 30 ml sealed glass tubes. The surrogate oil is a sweet light crude with similar analytical and toxicological properties to the MC252 oil discharged during the Deepwater Horizon disaster that was set aside by BP as a tractable model oil for experimentation. Experimental treatments included: unamended (UN) microcosms to which no nutrient was added and nutrient amended (NA) microcosms that received 32 μM ammonium and 2 μM phosphate (final concentration). Microcosms with no oil addition were constructed and incubated at 25 °C to indicate the amount of respiration supported by recently-produced natural organic matter present in seawater at the time of sampling. Triplicate microcosms were incubated in the dark at 6 different temperatures spanning the temperature range of polar to tropical climates (4, 8, 19, 25, 30, and 38 °C) for 15 days. Microcosms were sampled at regular intervals for respiration rate measurements.
Five milliliters of seawater from each site were incubated with 0.5% Macondo surrogate oil at 6 different temperatures (4, 8, 19, 25, 30, 38 degrees C) and two different nutrient conditions (no nutrient addition, 32 uM Nh4Cl, and 2uM K2HPO4) in triplicates. No oil addition control of each site was incubated at 25C without oil and nutrient addition.
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