Corrected 23 August 2010; see below www.sciencemag.org/cgi/content/full/science.1195223/DC1 Supporting Online Material for Tracking Hydrocarbon Plume Transport and Biodegradation at Deepwater Horizon Richard Camilli,* Christopher M. Reddy, Dana R. Yoerger, Benjamin A. S. Van Mooy, Michael V. Jakuba, James C. Kinsey, Cameron P. McIntyre, Sean P. Sylva, James V. Maloney *To whom correspondence should be addressed. E-mail: [email protected]Published 19 August 2010 on Science Express DOI: 10.1126/science.1195223 This PDF file includes: SOM Text Figs. S1 to S12 Tables S1 and S2 References Correction: In the original version of table S1, the Signal Transduction specifications of the two fluorometers were transposed.
Tracking Hydrocarbon Plume Transport and Biodegradation at Deepwater Horizon
Richard Camilli,* Christopher M. Reddy, Dana R. Yoerger, Benjamin A. S. Van Mooy, Michael V. Jakuba, James C. Kinsey, Cameron P. McIntyre, Sean P. Sylva, James V.
Maloney
*To whom correspondence should be addressed. E-mail: [email protected]
Published 19 August 2010 on Science Express DOI: 10.1126/science.1195223
This PDF file includes:
SOM Text Figs. S1 to S12 Tables S1 and S2 References
Correction: In the original version of table S1, the Signal Transduction specifications of the two fluorometers were transposed.
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Tracking hydrocarbon plume transport and biodegradation at Deepwater Horizon Richard Camilli1*, Christopher M. Reddy2, Dana R. Yoerger1, Benjamin A.S. Van Mooy2, Michael V. Jakuba3, James C. Kinsey1, Cameron P. McIntyre2, Sean P. Sylva2, James V. Maloney4 manuscript number: 1195223 Supporting Online Material This supplement contains: I. Still images of oil in the water column II. Ship-lowered rosette III. Conventional oceanographic water column profiling IV. Dissolved oxygen analysis and potential cross sensitivity to oil V. Sentry AUV VI. AUV characterization of horizontal plume structure VII. Plume cross section 16 km downrange of source Figs. S1 to S12 Tables S1, S2 References
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I. Still images of oil in the water column
Fig S1: Remotely operated vehicle (ROV) still images taken during descent through the water column from a location less than 500 m southwest of the well site on June 1, 2010. Still images were recorded from a forward looking video camera on the ROV. A highly turbid oil-emulsion layer was evident in the depth region between 1065 and 1300 m, with small oil droplets temporarily collecting on the camera lens within this depth interval. (photos: R. Camilli, WHOI)
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II. Ship lowered rosette
Fig. S2: Rosette being lowered from the R/V Endeavor during water column profiling operations. The TETHYS mass spectrometer is visible within the lower right portion of the rosette frame. The Rosette also included 12 Go-Flo water sample bottles (photo: C. McIntyre, WHOI)
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III. Conventional oceanographic water column profiling
Fig. S3: Plot of physical water column properties (simultaneously recorded with Fig. 1 data) 4km from the well site (28.7352º N 88.3892º W) on June 28, 2010.
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IV. Dissolved oxygen analysis and potential cross sensitivity to oil
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Fig. S4: Water column oxygen profiles from study area. Electrode-based oxygen sensors (SBE 43) recorded data continuously during Go-Flo bottle rosette casts and reported several oxygen minimum layers. These layers were targeted for oxygen analysis using Winkler [S1] oxygen titrations, with particular emphasis on the depth interval 1,000 to 1,200 m where the minimums were most pronounced. Winkler titrations indicated that water samples collected with Go-Flo bottles from these minimum layers almost always contained significantly more oxygen than indicated by the oxygen sensor. Of the 34 samples analyzed between 1,000 and 1,200 m, only 5 showed appreciable oxygen depletion, and 4 of these 5 samples still contained more oxygen than indicated by the oxygen electrode. As pointed out in an application note from the manufacturer of the oxygen sensor [S2] hydrocarbon contamination can lead to erroneously low oxygen readings from the sensor. We observed very clear evidence of this in the oil-contaminated surface waters; we observed anomalously low oxygen readings at the beginning of each downcast, but the oxygen readings quickly returned to normal values once the sensor was below the oil-contaminated layer. Winkler [S1] titrations were conducted using the method of Carpenter [S3] with seawater collected in 300 mL glass BOD bottles. We employed a Metrohm 785 DMP Titrino titration instrument equipped with a Metrohm Pt Titrode. All reagents and standards were prepared fresh for the cruise during the week of June 7, 2010. The sodium thiosulfate titration solution was certified 0.1000 N (Fisher Scientific), and was stored and titrated from a CO2-excluding reagent bottle. A 0.01000 N potassium iodate standard was run before every batch of samples; repeated analysis of this standard yielded a value of 0.01002 ± 0.00008 N (mean ± standard deviation; n=8). Seawater samples were obtained from 10-liter Go-Flo bottles on the CTD rosette immediately upon retrieval and before any other samples were taken. Triplicate seawater samples were collected from 65 m at a practice station on the way to the study site, and precision was found to be 0.17 micromoles L-1 (µM). Samples collected from ≈1,500 m at various locations throughout the study area yielded an average oxygen concentration of 215 ± 3 (mean ± standard deviation; n=6; one outlier not included, see Fig. S4, which is in excellent agreement with climatological data [S4]
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Fig. S5: Profiles of dissolved oxygen (oxygen microelectrode), CDOM (SUVF fluorometer), aromatic hydrocarbons (AQUAtracka fluorometer), and hydrocarbon indicator ions (TETHYS mass spectrometer) at two representative stations WSW of the well site. Station 28.7300oN 88.4274oW was approximately 6 km from the well site, while station 28.7053ºN 88.5263ºW was approximately 16 km from the well site. These profiles were recorded on June 25 and 26, 2010, respectively and correspond to Winkler titration measurements described in Fig. S6. Oxygen microelectrode and CDOM fluorometer measurements are expressed on an absolute scale, whereas aromatic fluorometer values are expressed on a relative (log) scale; mass spectrometric measurements are ratioed with water (m/z 17) to correct for variability in instrumental response; concentration values are unitless (expressed on a relative scale).
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Fig. S6: Profiles of oxygen concentrations determined by Winkler titrations at two representative stations WSW of the well site. The station 28.7300oN, 88.4274oW was approximately 6 km from the well site, while the station at 28.7053ºN 88.5263ºW was approximately 16 km from the well site. These profiles were collected on June 25 and 26 2010, respectively. The oxygen concentrations at the two stations were indistinguishable from one another (1140m to 1200m, Mann-Whitney, p = 0.1443). We estimate that the plume at the station 16 km from well site was ≈ 1.5 days older than at the station 6 km from the well site, but a distinct signature of plume-driven microbial respiration had yet to develop. This observation is consistent with our estimate that microbial respiration was not appreciably more than 1 µM O2 day-1 within our study site.
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V. Sentry AUV
Fig. S7: Photo of Sentry AUV during recharge between dive missions at the Deepwater Horizon spill site. The TETHYS payload is hidden within Sentry’s lateral port area, between the forward and aft dive planes (photo: D. Yoerger, WHOI). The Sentry autonomous underwater vehicle is designed for seafloor and water column survey to depths of 4500 m. Unlike ROVs, Sentry has no physical connection to the surface and is controlled by on-board computers. Sentry is based on a predecessor generation deep marine survey AUV, the Autonomous Benthic Explorer (ABE), [S5]. Sentry carries a modular sensor payload including bathymetric sonars and a digital still camera for seafloor mapping as well as chemical sensors for water column analysis, including conductivity, temperature, and turbidity as well as sensors measuring dissolved oxygen and redox potential. For these surveys, Sentry also carried a TETHYS mass spectrometer.
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The vehicle's software can autonomously make limited decisions as to survey optimization. For example, the vehicle can autonomously resurvey areas deemed to have high value at improved spatial resolution or using a specific sensing protocol. Sentry can send and receive messages to and from the surface using acoustic modems. These modems are reliable over moderate ranges (< 3km) and handle short data packets. Sentry sends messages containing updates of vehicle state, battery levels, and summaries of sensor data to the support vessel several times each minute. Additionally, human operators on the surface can alter Sentry's mission plan through a process of dynamic retasking. The data received from Sentry can be viewed as text or plotted using a display based on Google Earth. During these operations, Sentry acoustically telemetered summaries of sensor data, georeferenced to better than 5 m, in real-time to operators aboard the R/V Endeavor. The acoustic communications enabled extemporized input from the surface ship to redirect Sentry to amended depths and waypoints based on its real-time estimates of plume position. On three dives, Sentry covered 235 km at an average speed of 1.0 m s-1. Sentry ran at constant depth (standard deviation 0.013m) for the majority of this duration. In a few instances Sentry followed the seafloor at the prescribed minimum height of 80 m when the commanded depth brought it too close to the seafloor. On the second dive (Sentry #064), which was to the WSW, Sentry executed a preprogrammed zigzag pattern at constant depth. In real-time an elevated ion peak ratio associated with methane could be observed on each leg of the pattern. These observations showed that the preprogrammed plan was achieving a proper survey of the plume, so no retasking was initiated on that dive. On the last dive (Sentry #065), the retasking capability was critical to Sentry's operation. On several occasions tracklines and vehicle depth were modified to better track the plume.
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VI. AUV characterization of horizontal plume structure The TETHYS data from Sentry and the CTD tow-yos and casts are consistent with a 1100 m deep, continuous plume extending to the WSW of the spill site. All Sentry crossings revealed ion peak ratios well in excess of a statistically defined minimum extending for a distance averaging about 2 km for each crossing. CTD casts and tow-yos support an estimate of plume thickness. The Sentry deep plume survey was guided by the ion peak associated with methane in ratio to the water ion peak (m/z 15:17); this ratio assumes that any fluctuation in this water ion peak is due to variability in instrument response because the concentration of water in water is established. In post-processing, a statistical approach was applied to these TETHYS data to estimate the plume position. Our statistical methods for constructing the plume map (Fig. 3a) required that trackline segments exhibit increased signal intensity (methane:water). Signal increase was required to occur within isolated local maxima and with values above a statistically defined threshold two standard deviations above baseline values. Baseline was calculated using a mean absolute deviation filter with data binned in sections of 20 samples each. A least-squares line fit was then applied to identify this filtered baseline trend in order to compute the baseline’s standard deviation (Fig. S8). Data from Sentry also allows an estimate of the ambient water currents defined in a stationary world frame (Fig. S9). Sentry's Doppler velocity log (DVL) provides estimates of water velocity relative to the vehicle in a series of 30 bins extending out to 120 m below the vehicle. When in range of the seafloor (~200 m), the DVL also provides bottom-lock velocities. The water-lock doppler velocity in each of the four beams can be transformed into the vehicle frame. Vehicle velocity data from either the bottom-lock DVL or the external USBL navigation system can be used to remove vehicle motion from the estimate, and the INS allows the estimate in the vehicle frame to be transformed into world coordinates. Noise in the water-lock DVL estimates requires that these estimates be filtered in time to provide realistic estimates.
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Fig. S7: The upper panel (a) shows the raw ion-peak ratio data for each sample acquisition during survey operations on Sentry dives two and three. The baseline is shown as a thin black line in the upper panel, the red line designates the 2σ threshold. This cutoff was then used to isolate the plume sections, as shown in the lower panel. The lower panel (b) describes plume crossings (with numbered annotations) during each of the track line segments. The increase in signal intensity between crossings 16 and 17 is correlated with Sentry being retasked from its survey depth of 1110 m to a modified depth of 1160 m.
Data from Sentry also allows an estimate of the ambient currents defined in a stationary world frame. Sentry's Doppler velocity log (DVL) provides estimates of water velocity relative to the vehicle in a series of 30 bins extending out to 120 m below the vehicle. When in range of the seafloor (~200 m), the DVL also provides bottom-lock velocities. The water-lock doppler velocity in each of the four beams can be transformed into the vehicle frame. Vehicle velocity data from either the bottom-lock DVL or the external USBL navigation system can be used to remove vehicle motion from the estimate, and the INS allows the estimate in the vehicle frame to be transformed into world coordinates. Noise in the water-lock DVL estimates requires that these estimates be filtered in time to provide realistic estimates.
Fig. S8: The upper panel (a) shows the raw ion-peak ratio data for each sample acquisition during survey operations on Sentry dives two and three. The baseline is shown as a thin black line in the upper panel, the red line designates the 2σ threshold. This cutoff was then used to isolate the plume sections, as shown in the lower panel (b). The lower panel describes plume crossings (with numbered annotations) during each of the track line segments. The increase in signal intensity between crossings 16 and 17 is correlated with Sentry being retasked from its survey depth of 1110 m to a modified depth of 1160 m.
(a)
(b)
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Fig. S9: Profiles of the ion peak ratio signal associated with methane (m/z 15:17) are geospatially plotted. The z-axis represents raw ion peak ratio intensity (not plume height). The profiles are self-similar with a mean width of 2.3 km. Red arrows indicate georeferenced water current vectors calculated for each track line from Sentry's Doppler velocity log (DVL). The red circle and star indicate a 5.6 km (3 mile) radius vessel traffic exclusion zone and the Deepwater Horizon well site, respectively.
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VII. Plume cross section 16km downrange of source Vertical plume cross section was computed based on benzene, toluene, ethylbenzene, and total xylenes (BTEX) concentrations measured from Go-Flo bottle samples collected during vertical rosette casts at 28.7053ºN 88.5263ºW , 16 km from the well site on June 26, 2010 (Figs. S10 and S11). Samples were analyzed via gas chromatography by Alpha Analytical (Mansfield, MA) supported by NOAA's on-going NRDA program (Table S2). A vertical distribution profile was computed based on these samples, wherein the plume center was identified at 1111 m water depth. Although the concentration profile is strongly indicative of an extant vertical diffusive gradient throughout the plume, with an extrapolated maximum concentration at the plume center in excess of 90µg L-1, the maximum modeled concentration was truncated to equal the maximum measured concentration. The average BTEX concentration across the modeled 116 m vertical profile was calculated to be 26.7 µg L-1. Note that the two samples with the highest BTEX values in this profile were clear (Fig. S10; Table S2) Horizontal plume cross section was computed based on mass spectrometer measurements of methane distribution during AUV survey operations at 1120 meters water depth between track points at 28.6863ºN 88.5205ºW and 28.7050ºN 88.5390ºW on June 26, 2010. This section of trackline survey was chosen based on proximity to the previously described vertical rosette profile. The horizontal profile’s measured values exhibit clear evidence of a horizontal diffusive gradient throughout the plume. A model of the distribution profile was computed using the mass spectrometer methane data, wherein a relative hydrocarbon distribution is expressed on a percentage basis, with the maximum occurring at the plume center, and the minimum is defined as the plume threshold at two standard deviations above the root-mean-square baseline variability (Fig. S12). The modeled plume distribution uses only the leading side measurements in order to prevent latencies in signal relaxation from biasing the profile toward a larger cross section. The average horizontal hydrocarbon distribution across the modeled 778 m horizontal profile is calculated to be 33.7%.
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(a) (b)(a) (b)
Fig S10. Photographs of water samples collected for BTEX and other volatile organic compounds at (a) 1125 and (b) 1095 meters at 28.7053ºN 88.5263ºW, 16km from the well site on June 26, 2010 (Table S2) (Photo: Alpha Analytical, Mansfield, MA)
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Fig. S11: Vertical concentration distribution of monoaromatic hydrocarbons (BTEX) within the plume. Samples were collected at 28.7053ºN 88.5263ºW, approximately 16km SW of the well site on June 26, 2010.
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Fig. S12: Horizontal profile of relative methane distributions recorded by in-situ mass spectrometer at 1120 m water depth during AUV operations between track points at 28.6863ºN 88.5205ºW and 28.7050ºN 88.5390ºW on June 26, 2010. The center of the plume peak is located at 28.6969ºN 88.5313ºW, approximately 1 km downrange (SW) from the site of the vertical rosette profile shown in Fig.S11.
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Table S1: list of sensors deployed on ship’s profiling rosette during survey operations.
SENSOR MANUFACTURER MODEL ACQUISITION FREQUENCY
SIGNAL TRANSDUCTION DETECTOR
dissolved oxygen
SeaBird Electronics SBE43 1 Hz
Clark polarographic membrane
noble metal electrode
mass spectrometer
WHOI/Monitor Instruments TETHYS 0.1Hz
closed ion source cycloid m/z 2-200 Faraday cup
aromatic hydrocarbon fluorometer
Chelsea Instruments
AQUAtracka 1Hz
239nm excitation 360nm emission
photomultiplier tube
CDOM fluorometer Seapoint Sensors SUVF 1Hz
370nm excitation 440nm emission photodiode
turbidity Seapoint Sensors Turbidity meter 1Hz
Optical backscatter photodiode
conductivity SeaBird Electronics SBE 4C 1Hz Current
Platinum electrode
temperature SeaBird Electronics SBE 3plus 1Hz voltage potential thermister
depth ParoScientific Digiquartz 1Hz frequency change crystal oscillator
water velocity Teledyne RDI Workhorse 2Hz
acoustic Doppler backscatter
piezo ceramic 300kHz
Table S2: Concentrations of BTEX measured from Go-Flo bottle samples collected during vertical rosette casts at 28.7053ºN, 88.5263ºW on June 26, 2010.
Deployment Recommendations, and Cleaning and Storage. Application Note No. 64 (February 2010).
S3. J.H. Carpenter, The Chesapeake Bay Institute technique for the Winkler oxygen method. Limnol. Oceanogr. 10, 141–143 (1965).
S4. H. E. Garcia, R. A. Locarnini, T. P. Boyer, J. I. Antonov, in World Ocean Atlas 2005, S. Levitus, Ed. (U.S. GPO, Washington, DC, 2006), Vol. 3: Dissolved Oxygen, Apparent Oxygen Utilization, and Oxygen Saturation, p. 342.
S5. D.R. Yoerger, A.M. Bradley, M. Jakuba, C. German, T. Shank, M.A. Tivey, Autonomous and remotely operated vehicle technology for hydrothermal vent discovery, exploration, and sampling. Oceanography 20(1):152–161 (2007).
