Injury and Recovery of Sea Otters and Harlequin Ducks ... Population Recovery from the Exxon Valdez...
Transcript of Injury and Recovery of Sea Otters and Harlequin Ducks ... Population Recovery from the Exxon Valdez...
Injury and Recovery of Sea Otters and Harlequin Ducks following the Exxon Valdez
Oil Spill: a Quarter-Century PerspectiveDan Esler
Research Wildlife Biologist
Alaska Science CenterU.S. Geological Survey
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Oil in the Environment
Ingestion from
Preening
Ingestion of Contaminated
Prey
External Oiling
Background - Varying Mechanisms of Spill Effects on Wildlife
- Direct - Indirect
- Acute - Chronic
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Examples of Varying Timelines and Mechanismsof Population Recovery from the Exxon Valdez Oil Spill
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Examples of Varying Timelines and Mechanismsof Population Recovery from the Exxon Valdez Oil Spill
- Bald Eagle acute mortality observed
- Around 250 estimated to have died(about 10% of PWS population)
- Reproduction impaired for at least one year
By 1995, the Bald Eagle population had recovered and nochronic effects were observed (Bowman et al. 1997)
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Examples of Varying Timelines and Mechanismsof Population Recovery from the Exxon Valdez Oil Spill
Killer Whale numbers, in both resident and transient pods,dropped in association with the oil spill; acute mortality
Pre-spill numbers had not been achieved by 2013;indirect effects (demographic lags) (Matkin et al. 2012)
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Examples of Varying Timelines and Mechanismsof Population Recovery from the Exxon Valdez Oil Spill
Marbled murrelets and pigeon guillemots have been declining since the 1970s, due to changes in ocean conditions
There were almost certainly direct and indirect effects of the spill, but these are overwhelmed by larger processes
1970s 2010s
Exxo
n Va
ldez
spi
ll
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Sea Otter and Harlequin Duck Recovery Constrained by Lingering Oil
- Oil persisted in subsurface sediments
- Lightly weathered and toxic
- Lower intertidal zone affected
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Why Harlequin Ducks?
- concerns about population recovery in the immediatepost-spill years
- attributes that suggest vulnerability to spill effects:- nearshore habitats - benthic invertebrate diet
- high site fidelity - small body size
- near northern range limit - life history
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PWS - All
Years after spill0 5 10 15 20 25 30 35
Num
ber o
f fem
ales
0
4500
5000
5500
6000
6500
PWS - Unoiled area
Years after spill0 10 20 30 40 50 60 70
Num
ber o
f fem
ales
0
4000
4500
5000
PWS - Oiled area
Years after spill0 10 20 30 40 50 60 70
0500
1000
1500
2000
Harlequin Duck Demography
2013
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- one of a family of enzymes involved in metabolism and detoxification
- Cytochrome P450 1A (CYP1A) is induced by exposure to polycyclic aromatic hydrocarbons (PAHs) and PCBs
- CYP1A is a sensitive and specific indicator of oil exposure (as PCBs are not an issue in PWS)
Harlequin Duck Biochemical Indicators of Exposure
Cytochrome P450 1A
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Harlequin Duck Biochemical Indicators of Exposure
0
25
50
75
100
125ER
OD
Activ
ity (p
mol
/min
/mg) = oiled areas
= unoiled areas
November2006
March/April2007
March2009
March2011
March2013
March2014
Average (± SE) EROD Activity of Harlequin Ducks
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Critical Conclusions:
- Population-level effects of the Exxon Valdez oil spill and lack of population recovery persisted into late 2000s
- Recent data are consistent with recovery criteria set by the EVOSTC, indicating timeline to populationrecovery was between 20 and 25 years
Results for harlequin ducks indicate:
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Why Sea Otters?
- concerns about population recovery in the immediatepost-spill years
- attributes that suggest vulnerability to spill effects:- nearshore habitats - benthic invertebrate diet- thermoregulatory/metabolic challenges
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Years76-89 (pre-spill) 89 (spill) 90-08 10-13
Rel
ativ
e Fr
eq.
0.0
0.1
0.2
0.3
0.4
0.5
0-1 yrs 2-8 yrs >8 yrs
(215)
Sea Otter Ages-at-Death –Western Prince William SoundSea Otter Ages-at-Death –Western Prince William Sound
Years76-89 (pre-spill) 89 (spill) 90-08 10-13
Rel
ativ
e Fr
eq.
0.0
0.1
0.2
0.3
0.4
0.5
0-1 yrs 2-8 yrs >8 yrs
(215) (419) (530)
Sea Otter Ages-at-Death –Western Prince William Sound
Years76-89 (pre-spill) 89 (spill) 90-08 10-13
Rel
ativ
e Fr
eq.
0.0
0.1
0.2
0.3
0.4
0.5
0-1 yrs 2-8 yrs >8 yrs
(215) (419) (530) (166)
Sea Otter Demography
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Critical Conclusions:
- Population-level effects of the Exxon Valdez oil spill and lack of population recovery persisted into late 2000s
- Recent data are consistent with recovery criteria set by the EVOSTC, indicating timeline to populationrecovery was between 20 and 25 years
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- Wildlife species vary widely in vulnerability to oil spill effects
- Spill effects on wildlife can be manifested through a wide array of mechanisms, not just direct, acute
- For some species, chronic exposure to residual oil can have effects as large as direct, acute effects
- The timeline over which recovery occurs varies by species; for some, it may be measured in decades
Overall Implications
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ACKNOWLEDGEMENTS
Photo Credits: Randy Davis, Tim Bowman, Mandy Lindeberg, Dan Esler, Ken Wright, Exxon Valdez Oil Spill Trustee Council, John Pearce
Funding and Support: Exxon Valdez Oil Spill Trustee Council, USGS –Alaska Science Center, USGS – Western Ecological Research Center, Simon Fraser University, Pacific Wildlife Foundation, Gulf Watch Alaska, National Park Service, NOAA
Field, lab, and administrative work conducted by a small army of peopleover the years – thanks to all.
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