6/12/2018 1 An ocean of oil… Rapid sedimentation and accumulation at the seafloor in the aftermath of the Macondo Blowout Samantha Joye Department of Marine Sciences University of Georgia Contributors: Patricia Medeiros, Kimberley Hunter (U Georgia); Uta Passow (UCSB); Arne Diercks (U Mississippi); Vernon Asper (U Southern Mississippi); Joe Montoya (GA Tech); Andreas Teske, Tingting Yang (U North Carolina); Claudia Benitez‐Nelson and Willard S. Moore (U South Carolina) Emulsified oil on the surface Hydrocarbon jet from BOP stack Pre‐Macondo view of the fate of oil derived from a deepwater blowout Peterson, Joye et al. 2012 BioScience
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6/12/2018
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An ocean of oil…Rapid sedimentation and accumulation at the seafloor in the aftermath of the Macondo
Blowout
Samantha Joye
Department of Marine Sciences
University of Georgia
Contributors:
Patricia Medeiros, Kimberley Hunter (U Georgia); Uta Passow (UCSB); Arne Diercks (U Mississippi); Vernon Asper (U Southern Mississippi); Joe Montoya (GA Tech); Andreas Teske, Tingting Yang (U North
Carolina); Claudia Benitez‐Nelson and Willard S. Moore (U South Carolina)
Emulsified oil on the surface
Hydrocarbon jet from BOPstack
Pre‐Macondo view of the fate of oil derived from a deepwater blowout
Peterson, Joye et al. 2012 BioScience
6/12/2018
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Emulsified oil on the surface
Hydrocarbon jet from BOPstack
Post Macondo view – seafloor accumulation is significant
Peterson, Joye et al. 2012 BioScience
The day it started: Sept. 6, 2010
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• Biological emulsification and sinking of oil‐snow• Dispersant‐mediated coagulation and sinking
• Multiple “plume” layersthat eventually intersect with the continental slopeand contaminate sediments with plume‐derived oil, etc.
Aug 2010 example
• Discussion topic: to what extent is vertically sinking material laterally entrained along (plume) isopycnals and deposited subsequently at slope intersection points?
Evidence of Accumulation, July‐Dec 2010 Study Area
Source: Joye et al. in prep; data from Pat Medeiros
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Burning – an unexpected pathway to the bottom
0.8
September 2010
Pyrogenic Index (PAHs, top sediments)Wang et al. (1999) ES&T
MC252
28
26
1718
22
20
Source: Joye et al. in prep
15 µg/L
Elemental Carbon (Thermal‐optical method)MUC core overlying water
Pyrogenic Signatures
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MC252
5 nmol/cc/d
Microbial Activity(average SR rate in interval)
vs
28
26
1718
22
20
*natural seep ~ 100+
Source: Joye et al. in prep
Impacts: reduced microbial activity
Impacts: reduced diversity/abundance of benthic fauna
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Summary• Multiple mechanisms (biological, pyrogenic, dispersant) and seafloor “expressions” of weathered oil deposition
• The relative importance of burn residue vs. biological deposition vs. dispersant‐mediated deposition remains to be determined
• concentrations of TPH, PAH, petroleum biomarkers, and UCM were elevated above background, esp. within 40 miles; not natural seeps!!
• microbial activity reduced in these layers (reduced biomass, inhibition, toxicity…)
• filter feeding fauna at the seafloor was suffocated by thisunprecedented sedimentation event – how long it will takethese communities to recover is unknown.