peterson - the College of Marine Science

Ocean Conservancy – GOMURC Workshop
April 2012
Charles H. “Pete” Peterson
University of North Carolina at Chapel Hill
DWH Blowout – Two Types of Oil Spills
Type I - Familiar Spill
 Composite of nearshore oil spills
 Fate:
 Oil rises to the surface
 Floating oil grounds on shores
 Effects:
 Surface organism mortality
 Intertidal habitats fouled
 Shallow subtidal contamination
 Sublethal effects induce pop losses
Type I
Type II
Type II - Deepwater Spill
 Novel offshore, deep-water
blowout of oil and gas
 Fate:
 Extensive fine dispersion of oil &
gas via turbulent pressurized
injection into cold seawater
 Retention in plumes at depth
 Surfacing and grounding of oil
 Broad deposition on sea floor
 Effects:
 Surface organism mortality
 Intertidal habitats fouled
 Bio exposures in water column
 Widespread benthic mortalities
The Deepwater Horizon Spill
oil slick
200 m
oil plume
500 m
finely dispersed subsurface oil plume
finely dispersed oil/hydrate plume
1000 m
1500 m
1800 m
oil on
Oil Spill Oceanography
0 to 200 m
Complex Physics and Chemistry
Thick Oil
1000 m
4000 m
Adsorption and Adherence
to Particulates
Legacy of the Exxon Valdez Oil Spill
 Of all oil spills, EVOS impacts are the most
thoroughly studied in scope, duration, and roles of
ecosystem-based interconnectivity of natural
resource impacts
 Explicit impact studies of EVOS are relevant to the
Type I components of DWH (surface and
shorelines), but offer only procedural insights to
guide impact assessment of DWH Type II
 EVOS helps guide the processes of impact
assessment and restoration by example, good and
 EVOS brings new insights into ecotoxicological
mechanisms and processes – new paradigms only
slowly incorporated into injury models
Photos: Anchorage Daily News
Exxon Valdez Oil Spill = EVOS Deepwater Horizon Spill = DWH
Myths Debunked and Emerging
Paradigms Created by EVOS Science
 Significant toxicity is not limited to acute
exposure to BTEXs, but continues for
decades via exposure to buried oil
sequestered in biologically accessible,
but anoxic reservoirs
 Toxicity of chronic exposures to PAHs
occurs at ppb concentrations, much
lower than the ppm water quality
standards (based only on acute
exposures to water-soluble fractions
from fresh oil)
 Clean-up and restoration responses can
be more injurious than the oil
benzene, toluene, ethylbenzene, and xylenes = BTEX
polycyclic aromatic hydrocarbons = PAH
Novel Scientific Insights from EVOS
 Sublethal impacts (affecting individual growth,
reproduction, behavior) may have serious effects at
the population level and must be incorporated
into the injury assessment process
 Major physical effects of oil (smothering, fouling of
feeding apparatus, etc.) can continue to operate
independent of chemical toxicity of the oil
 An ecosystem-based approach is critical to
account for interactions and indirect effects that
ramify through the interaction webs; this coupled
with long-term monitoring is the only way to
understand some delayed and long-term impacts
of the oil spill
Deepwater Horizon Timeline
 April 20 – well blow-out and fire @ 21:45 h
 April 22 – first surface oil slick detected
 May 1 – surface application of dispersant began
 May 14 – injection of dispersant at well-head began
 July 15 – oil and gas discharge ended (after 84 d)
6 to 8
Comparative Spill
Oil Volumes
DWH: 4.9 million barrels of oil, 14.7 million ft3 of gas
1.8 million gallons of dispersant added
 1.07 million gallons at sea surface
 0.77 million gallons at the well-head
1.5 to 1.9 x more gas released than oil by mass
million barrels of oil
Kuwait oil field DWH
Ixtoc I
Exxon Santa Barbara
Natural Resource Injuries from the
Type I Portion of the DWH Incident
 The “easy” part – long agency (NOAA)
experience/skills directly applicable here to
surface and shoreline habitat oiling impacts
 Potentially trivial compared to novel subsurface
ecosystem impacts ?
 May form the vast majority of the focus of
restoration because:
 Better capacity to infer injuries
 Ecosystem values and uses to humans understood
 Compensatory restoration is deemed feasible
 Political pressure for state “wish list” projects
Type I Injuries: Species Oiled at Sea Surface
 Seabirds found dead in oiled areas in USFWS counts to 12/2011
 gulls = 2901
 brown pelican = 556
 northern gannet = 441
 royal tern = 233
 black skimmer = 233
 Sea turtles – 613 dead (incl. Kemp’s ridleys) in NOAA counts from
 Marine mammals – 452 dolphin strandings in NOAA data base out
of 625 total cetacean strandings from 4/2010-1/2012; abnormally
high miscarriage rates
 Fish –concerns about impacts on early life stages because of
dispersed oil in fine droplets is so highly bioavailable and to
nearshore demersal fish like killifish in contact with oil
 Blue crab and penaeid shrimps – still under study but clearly
extensive exposure to oil and dispersants
 Floating Sargassum community – high risk and likely injury to
habitat provider (plant) and associated fish and wildlife – incl. dead
hatchling sea turtles; concern over larval & juvenile bluefin tuna,
mahi, cobia, etc.
Type I Injuries: Shoreline Habitats Oiled
(1053 linear miles)
 Coastal marsh – especially margins, where below-
ground plant mortality also fostered marsh edge
erosion but low total acreage lost
Sandy ocean beaches – coatings of mousse,
tarballs, and layers of buried oil at depths in the
sand with intense disturbance of clean-up
Seagrass beds – some direct habitat loss
Oyster reefs – some mortality from smothering
plus possible oyster larval mortality; mass
freshwater diversion mortality
Protected mudflats – some loss of benthic
invertebrate prey for higher trophic levels
Estuarine muddy bottom and ocean floor – PAH
contamination plus persistence of oiled detritus,
evident during summer 2011 storms
Type I Injuries: Grounded
Oil Effects on Shoreline
 Ground- and low-nesting marsh birds (double jeopardy for
pelicans etc. = feeding at sea + nesting impacts).
Fiddler crabs, blue crabs, and marsh nekton, esp. shrimps.
Oysters by adult and juvenile mortality, larval losses, and
likely slower growth.
Terrapins and marsh mammals.
Nekton, including juvenile and resident fishes (killifish), that
use shallow marsh, oyster reef, seagrass habitats.
Seaducks, sea turtles, and demersal fishes that eat benthic
invertebrates in shallow estuarine bottom are at risk.
Collateral Injuries: from Response Actions
 Toxicity from chronic exposure to persistent dispersant
- alone and with oil
 Fine-scale chemical dispersal of oil enhanced bio-
availability and kept it sub-surface for longer, thereby
magnifying impacts to zooplankton, particle feeders
 Physical injuries to marsh from boom groundings and
vessel groundings while deploying boom
 Waterbird mortalities from “booming in” both oil and
birds around marsh islands
 Habitat and food-web degradation from beach
“nourishment”, which kills benthic invertebrates
 Oyster mortality from of freshwater diversions
 Air pollution and health effects in wildlife and humans
from soot creation during at sea burning
Collateral Injuries: from Clean-up Efforts
 Vehicle driving on beaches (especially at night)
U.S. Coast Guard
destroyed nests, killed nesting birds/chicks
Birds and other animals killed during uptake into
oil skimmers
Construction of coastal barrier berms killed
benthic food resources and misguided sea turtles /
ground-nesting birds to nest on that rapidly
eroding sand
Sea turtle mortalities from intense trawl fishing,
perhaps with disabled TEDs, immediately before
closures when enforcement attention was diverted
Repeated mortality of benthic invertebrates and
consequent loss of prey from demersal surf fishes
and shorebirds after beach excavations to remove
buried tarballs and oil layers and raking up wrack
Injuries: Type II Oil Spill Impacts
(Subsurface including Deep Ocean)
 By far the hardest aspect of the DWH spill
to assess, requiring new research on
interdisciplinary oil-spill oceanography
 Possibly largest portion of the ecosystem
impacts of the hydrocarbon release
 Effective restoration depends on scientific
advances to understand direct and indirect
ecosystem impacts and service losses in
meso-pelagic, bentho-pelagic, and deepbottom communities
 Failures by government and industry to
conduct necessary science for readiness
Subsurface Ecosystem Consequences of
a Deep-water Blowout
 3 broad categories of subsurface impacts from the DWH
1. Toxicity of oil and dispersant (includes physical smothering and
fouling) – pelagic particle feeders and all guilds of benthos
2. Implications of organic carbon loading (perhaps 0.5-3.0 x annual
production over the spill area) with resultant intense microbial
heterotrophic production and CO2 injection into seawater
3. Indirect effects of food web disruption – likely a widespread fracture
of the food-chain linkage from particle feeders to higher trophic
levels – including (?) species like sperm whales
 2 ecological compartments outside familiar scope of NRDA
1. pelagic (mostly deep) water column
2. deep benthos
Type II Effects of DWH Oil Spill:
Glimpses of Pelagic Impacts
M. Joye
 Extensive mortality by fouling the feeding and respiratory organs of pelagic
particle feeders such as copepods, salps, and appendicularians, thereby
fracturing the food chain linkages to higher trophic levels
Massively elevated heterotrophic microbial production and consequent
oxygen sags detected in petroleum hydrocarbon plumes trapped at a
pycnocline in 800-1,100 m, but oxygen not depleted enough to induce
Microbial production has been associated with marine snow and slime that
helped aggregate oil droplets with organic particles and induce transport the
oil to the deep sea floor
Study of higher trophic levels could integrate impacts to food chains, taking
opportunity to use the spill as an oceanographic experiment
The high likelihood of large indirect food-web effects from DWH oil implies
that delayed injuries will emerge, detectable only if focused ecosystembased injury assessments continue over sufficient time
Type II Effects of DWH Oil Spill:
Glimpses of Deep Benthos Impacts
 Deposition of dark, hydrocarbon-rich sediments
mm-cm thick onto sedimentary bottoms
appears to have caused widespread mortality of
resident soft-bottom benthic invertebrates,
perhaps by smothering (Joye)
 Some emergent hard-bottom areas exhibit
apparent cover by a similar dark material and
exhibit mortality of soft corals, sea fans, brittle
stars, and other inverts (Fisher)
 After the early bloom of heterotrophs, microbial
activity now appears grossly suppressed on the
sedimentary seafloor
Guiding Principles for GoM
Ecosystem Restoration
from 2011 Pew Report
 Recognizing that past human and natural perturbations have
compromised Gulf ecosystem function and resilience
 Acknowledging that dramatic environmental change is
inevitable and must be integrated into restoration plans
 Treating the Gulf as one interconnected network of ecosystems
from the shoreline to the deep sea
 Realizing that ecosystem productivity, health, and sustainability
of the Gulf and human welfare are intrinsically codependent
Acknowledged Contributors
NCEAS Working Group:
Sean Anderson, Gary Cherr, Rich Ambrose, Shelly Anghera, Steve
Bay, Michael Blum, Rob Condon, Tom Dean, Monty Graham,
Michael Guzy, Stephanie Hampton, Samantha Joye, John
Lambrinos, Bruce Mate, Doug Meffert, Sean Powers, Ponisseril
Somasundaran, Bob Spies, Caz Taylor, Ron Tjeerdema, Charles
Peterson : paper now posted on-line in BioScience May 2012.
Ocean Conservancy Team:
Stan Senner, Jeff Short, Chris Haney, Bob Spies, Lisa Suatoni, Paul
Kemp, Dennis Kelso, Charles Peterson

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