Deepwater Horizon Oil Spill Ecosystem Impacts
Kendra Daly & Colleagues
University of South Florida
Deepwater Horizon Oil Spill Ecosystem Impacts
& Ecosystem Impacts on Oil
Kendra Daly & Colleagues
University of South Florida
Marine Food Web
Humans
Apex Predators
Large Fish
Forage Fish
Zooplankton
0.01
unit
0.1 unit
1 unit
10 units
100 units
Base of Food Web
Phytoplankton
1000 units
Challenges to Understanding Deepwater Horizon Oil
Spill Ecosystem Impacts
• Lack of historical baseline data. What did a “normal”
ecosystem look like before the oil spill?
• Assess Oil Impacts in relation to a very complex
ocean environment that is constantly changing
Challenge: Assess Oil Impacts vs. Time Varying Ecosystem Complexity
August 2010
Dr. Ruoying He (NCSU) Model http://omgsrv1.meas.ncsu.edu
Challenge: Assess Oil Impacts vs. Time Varying Ecosystem Complexity
August 2013
Dr. Ruoying He (NCSU) Model http://omgsrv1.meas.ncsu.edu
Creating a Knowledge Base of Ecosystem Complexity
at Low Trophic Levels
In Situ Time-Series: May 2010 – August 2013
• Completed 20 cruises since May 2010, alternating between the WFS and N Gulf
• Measurements include: CTD, nutrients, PAR, chlorophyll, optical backscatter,
phytoplankton ID, POC, C&N uptake rates, DCMU (phyto-photophysiology),
HPLC, bongo net tows, SIPPER imaging system tows
Impact on Phytoplankton: Satellite Data
Surface oil
presence statistics
Phytoplankton
fluorescence
anomaly, Aug 2010
[Hu et al. 2011, GRL]
Oil Impacts on Phytoplankton: August 2010
• Satellite detected higher phytoplankton concentrations (> 1 mg m-3)
than previous 8-year mean in Northern Gulf of Mexico. High
chlorophyll measured in field (2 mg m-3) (Hu et al. 2011 GRL).
• Some stations and depths had waters toxic to bacteria (21%) and
phytoplankton (34%) correlated with oil. 43% sites had DNA
damaging activity. Phytoplankton photosynthetic capacity
decreased at some sites/depths (Paul et al. 2013, Envir. Sci. Tech. 47
)
• Phytoplankton diversity decreased at
sites near DWH
Diatom dominated community
Thalassionema nitzschioides
Dactyliosolen fragilissimus
Leptocylindrus minimus
Pseudo-nitzschia spp.
Phytoplankton images courtesy of FWRI
Impacts on Zooplankton: SIPPER Imaging System
June 2010: Photograph of crude oil aggregates observed in the
surface waters near the DWH site aboard the RV Gordon Gunter.
June 2010: SIPPER image of crude oiled marine snow aggregates
observed near the surface in close proximity (< 5 km) to the Deepwater
Horizon rig during aboard the RV Gordon Gunter.
Oiled
Non-oiled
SIPPER images of opaque detrital particles collected within 20 miles of the DWH
leak site from three separate cruises between May - August 2010.
A large portion of the petro-carbon emitted during oil
spill was methane (30%). Where did that go?
By 2011, 5 - 15% of fossil
carbon from methane found
in the zooplankton.
Possible bioaccumulation
transfer to fish and marine
mammals.
Cherrier et al. 2013. Env. Sci and Technology Letters
Chanton et al. 2012. Environmental Research Letters 7
SLOPE of Mixing Line indicates
methane as fossil C source
Impacts of Ecosystem on Oil Sedimentation
• Marine snow includes mucus producing bacteria,
dying or dead phytoplankton, zooplankton,
zooplankton gelatinous houses and fecal material
• Natural process that produces a sticky webbing matrix
and plays an important role in material sinking out of
the water column
• Sedimentation of oil associated with marine snow
particles was not taken into account in the oil budget
calculation
Fate of Oil: Oil Budget Calculator (NOAA August 2010)
Early estimates of liquid-oil budget: ~30% removed; ~70% in
environment. What fraction is in offshore sediments?
MOSSFA
Marine Oil Snow Sedimentation and Flocculant
Accumulation
Inter-Consortia GoMRI Working Group
(U. Passow & D. Hollander, J. Chanton, K. Daly)
Highlights
(1) Understanding the impact of the oil spill is challenging due to the lack of
historical data and complex changing environment.
(2) Impacts of oil on lower food web (small plants and animals) include:
(a) August 2010 (one month after oil spill)
• Oil toxic to bacteria & phytoplankton and DNA damage at some stations
and depths. Decreased phytoplankton photosynthesis (stress)
• Phytoplankton bloom east of wellhead, high zooplankton, and high
marine snow concentrations sink to seafloor
(b) September 2011 (one year after oil spill)
• Some sites/depths still toxic to phytoplankton
• Decreased zooplankton, especially some species, due to oil spill or
environmental variation?
• 5 - 15% of methane from oil spill found in zooplankton, obtained by
ingesting small particles from bacteria that degrade methane
(3) Sinking oil-associated marine snow was an important pathway by which oil
was removed from the water column and reached the sea floor. Should be
considered for future oil spill response efforts and oil budget calculations.