LongLong--term Ecosystem term Ecosystem Responses to Responses to

the Exxon Valdez oil spillthe Exxon Valdez oil spillJ.L Bodkin, C.H. Peterson, S.D Rice, J.W. Short, J.L Bodkin, C.H. Peterson, S.D Rice, J.W. Short,

D.E. D.E. EslerEsler, B.E. Ballachey, D.B. Irons, B.E. Ballachey, D.B. Irons

Science 2003 v 302 :2082Science 2003 v 302 :2082--20862086

OutlineOutlineThe setting, the spill, acute effects and assumptionsThe setting, the spill, acute effects and assumptions

Shoreline/damage assessments Shoreline/damage assessments

Population assessmentsPopulation assessments

Delayed recoveries; why? Delayed recoveries; why?

Lingering oil and routes of exposureLingering oil and routes of exposure

Ecological cascadesEcological cascades

Revising oil pollution risk assessment Revising oil pollution risk assessment

PRINCE WILLIAM SOUNDPRINCE WILLIAM SOUND

Two Marine Ecosystem Components Two Marine Ecosystem Components

OffshoreNearshore

LINKS

DISTINCTIONS

Nutrient exchangeEgg/larvae/juvenile transportMigration/life cycles

Macroalgae-drivenBenthic inverts pathwaySpace limitedSubstrate importantDepth limits

Phytoplankton-drivenZoo/Fish pathwayNutrient limitedLight limitedExtreme depths

Nearshore Offshore

Offshore WebOffshore Web

Nearshore WebNearshore Web

Exxon ValdezExxon ValdezOil SpillOil Spill

42 million liters of crude oil spilled

March 24, 1989

100 Miles

Kodiak Is

Alaska P

eninsula

Kenai Pen.

Prince WilliamSound

Alaska

Gulf ofAlaska

The The Exxon ValdezExxon ValdezOil SpillOil Spill

Then and Now

-- Conventional assumptions about effects of oilConventional assumptions about effects of oilpollution on wildlife populations:pollution on wildlife populations:

- direct, acute effects are most important

250,000 dead seabirds, 3,000 dead sea otters

-- Conventional assumptions about effects of oilConventional assumptions about effects of oilpollution on wildlife populations:pollution on wildlife populations:

- direct, acute effects are most important

- oil is removed quickly by natural processes

-- Conventional assumptions about effects of oilConventional assumptions about effects of oilpollution on wildlife populations:pollution on wildlife populations:

- direct, acute effects are most important

- oil is removed quickly by natural processes

- therefore, long-term chronic oil exposureis not a problem, and affected populations should rebound from acute mortalities in a short period of time (months to a few years)

Not Necessarily………

Shoreline and Clean up and Shoreline and Clean up and Damage AssessmentDamage Assessment

1989-1991 assessments of oiled shorelines

Shoreline Assessment ResultsShoreline Assessment Results::1989: 2,000 km of oiled beach1992: 11 km of oiled beach,

1.15 ha subsurface oil (2.8 ac)

1992 Shoreline Assessment Conclusions:1992 Shoreline Assessment Conclusions:

Oil mostly in upper intertidalOil rapidly dispersing

Oil on PWS Beaches: 1989 Oil on PWS Beaches: 1989 –– 20012001(Actual (Actual and Projected)and Projected)

But some injured species But some injured species are not recovering, why ?are not recovering, why ?

0

2000

4000

6000

8000

10000

12000

14000

16000

18000

20000

1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001

Year

Am

ount

Rem

aini

ng (m

^3)

Post SpillProjected

Nearshore Vertebrate PredatorsNearshore Vertebrate Predators1995

1995

NVP ApproachNVP Approach

Select top level nearshore predators that Select top level nearshore predators that represent:represent:

Birds and mammals Birds and mammals Invertebrate and fish trophic pathways, Invertebrate and fish trophic pathways, andand

Sample all populations in oiled and unoiled Sample all populations in oiled and unoiled areas (limited inference)areas (limited inference)

Study Areas

Types of DataTypes of Data

Have they recovered?Have they recovered?-- Population densityPopulation density-- Birth and survivalBirth and survival-- Health and conditionHealth and condition

Is it demography?Is it demography?-- Population modelsPopulation models

Is it food?Is it food?-- Prey abundancePrey abundance-- Predator conditionPredator condition-- Prey consumptionPrey consumption

Is it oil?Is it oil?-- CYP1ACYP1A-- Blood chemistryBlood chemistry-- HematologyHematology

How do we measure oil exposure?How do we measure oil exposure?

Cytochrome P450 1A (CYP1A) biomarker

• One of a family of enzymes involved in metabolism and detoxification

• Induced by recent exposure to polycyclic aromatic hydrocarbons (PAHs) and PCBs

• CYP1A is a sensitive and specific indicator of oil exposure

HARLEQUIN DUCK POPULATION TRENDSHARLEQUIN DUCK POPULATION TRENDSADFG Fall SurveysADFG Fall Surveys

1995 1996 1997

W. Prince William Sound (Oiled)

E. Prince William Sound (Unoiled)

0.7

0.8

0.9

MarchWeek

2 4 6 8 10 12 14 16 18 20 22 24 261 3 5 7 9 11 13 15 17 19 21 23 25October November December January February

Surv

ival

Pro

babi

lity

UnoiledOiled

1

Early Winter Mid Winter Late Winter

Adult Female Harlequin Duck SurvivalAdult Female Harlequin Duck SurvivalWinters 1995-96, 1996-97, and 1997-98Winters 1995-96, 1996-97, and 1997-98

Is it Food?Is it Food?

No difference in abundance of food at No difference in abundance of food at oiled and unoiled sitesoiled and unoiled sitesFood does not explain a significant Food does not explain a significant amount of variation in duck abundance amount of variation in duck abundance above that explained by other habitat above that explained by other habitat variablesvariables

Is it Oil?Is it Oil?

0

50

100

150

200

250

Montague Island (Unoiled)

Main Bay andCrafton Island (Oiled)

ERO

D A

ctiv

ity (p

mol

/min

/mg)

Average (Average (++ 95% CI) 95% CI) Cytochrome P450 1A Cytochrome P450 1A Induction in Harlequin Ducks - Winter 1998Induction in Harlequin Ducks - Winter 1998

Area

Sea Otter Recovery as of 1995Sea Otter Recovery as of 1995

Year

Estim

ated

pop

ulat

ion

size

0

50

100

150

200

Heavily oiled Knight Island

Minimum prespill Knight Island population size in 1989 (from Dean et al. 2000)

1989 1993 1994 1995

What can carcasses tell

us about survival?

Trends in Sea Otter Mortality in WPWS, 1977-1998 as represented by the ages of animals dying each year

Year

1975 1980 1985 1990 1995

Prop

ortio

n pr

ime-

age

dyin

g

0.0

0.1

0.2

0.3

0.4

0.5

0.6

Pre-spill

spillyear

Post-spill

Monson et al. 2002

Sea otter population trends and predicted trajectories based on estimated survival rates

Year1993 1994 1995 1996 1997 1998

Prop

ortio

n

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

WPWS

Northern Knight Is

Monson et al. 2000

Measures of Food AvailabilityMeasures of Food Availability(all significantly > at oiled sites)(all significantly > at oiled sites)

(Kj/hr) (min/d) (g/cm)

0

500

1000

1500

2000

2500

Consumption Foragingefficiency

Condition

oiledunoiled

Dean et al. 2002

Is it Oil?Is it Oil?Oil exposure in WPWS sea otters, 1996-98, indicated by P4501A

Molecules of CYP1A mRNA/ng RNA

<55 < 10

10 < 15

15 < 20

20 < 25

25 < 30

30 < 35

35 < 40

40 < 45

45 < 50> 50

% o

f sea

otte

rs

0

10

20

30

40

90

100

Unoiled area (n=86)

Oiled area (n=71)

CYP1A Biomarker - Results from NVP Study

SpeciesSpecies 19961996 19971997 19981998

Sea ottersSea otters >> >>Harlequin ducks Harlequin ducks >>

River ottersRiver otters >> == ==

>>>>

>>

BarrowBarrow’’s Goldeneyess Goldeneyes

Masked GreenlingsMasked Greenlings >>

Pigeon guillemot chicksPigeon guillemot chicks ==Pigeon guillemot adultsPigeon guillemot adults(1999)(1999) >>

Nearshore RecoveryNearshore Recovery

Fish eaters Invert eatersRiver PigeonRiver PigeonOtter GuillemotOtter Guillemot

Harlequin SeaHarlequin SeaDuck OtterDuck Otter

Recovered? Yes No No No

Is it food? _ Yes No No Is it oil? _ Possibly Yes Yes

NVP Conclusions (1999)NVP Conclusions (1999)

SO/HADU share habits and habitats in the SO/HADU share habits and habitats in the nearshorenearshoreElevated mortality constraining recovery Elevated mortality constraining recovery Elevated biomarkers of oil exposureElevated biomarkers of oil exposureAccumulating evidence linking residual oil Accumulating evidence linking residual oil and continuing injuryand continuing injury

So what is the source and route of So what is the source and route of exposure?exposure?

Revisit shoreline assessment assumptionsRevisit shoreline assessment assumptionsRevisit sampling intertidal sedimentsRevisit sampling intertidal sediments

Continue monitoring exposure through Continue monitoring exposure through biomarkersbiomarkers

Investigate pathways of potential exposureInvestigate pathways of potential exposure

EL056A

EL056C

Site Photo

Oil residue in pit

2001Shoreline survey for residual EVOS oil

Stratified Random Sampling Grid

100 m12.5m

A B C D E F G H+4.6m

+1.8m

0.51.0

1.5

2.0

2.5

3.0

1/2 meterdrops

96 randomly selected

pit locations

Total # random pits = 6,775

2001 Subsurface Oil -Light Oil Residue

Moderate Oil Residue

Heavy Oil Residue

LOR MOR

HOR

Intertidal Subsurface Oil

2001 survey (+6ft)

Oil

Majority of Subsurface oil(+8.2ft – 3.3ft)

+16ft - 0ft

2001

Sampled 91 sites

Results

53 sites with oil38 sites without

Estimated Oiled Area 2001Estimated Oiled Area 2001Surface Oil: 4.13 ha (2.07 – 7.05 ha)

Subsurface Oil: 7.80 ha (4.06 – 12.7 ha)

Total: 11.3 ha (17.2 – 6.78 ha)

1992 estimate = 1.5 ha of subsurface oil

0

200

400

600

800

1000

1200

1400

1992 1993 1994 1995 1996 1997 1998 1999 2000 2001

Year

Amou

nt R

emai

ning

(m^3

)

Post Spill2001 ABL

Oil on PWS Beaches: 1992 Oil on PWS Beaches: 1992 –– 20012001(Projected (Projected vsvs Actual)Actual)

ConclusionsConclusions• Oil more persistent than anticipated

• Intertidal biological zone more affected than anticipated

• Little long-termimpact on subtidal

Exposure to lingering oil in sea otters(work in progress)

Do they use the oiled habitats?And if so how much? 2002/03

Known Diet of Sea Otters at Knight IslandBased on Visual Observations in 2002 (N = 459)

Freq

uenc

y of

Occ

urre

nce

(%)

0

10

60

80

clam mussel bivalve crab urchin stars other

Time Depth Recorder ImplantsTime Depth Recorder Implants2003 and 20042003 and 2004

T im e (h rs )0 1 2 3 4 5 6 7 8 9 1 0 1 1 1 2

Dep

th (m

)

-8 0

-6 0

-4 0

-2 0

0

2 0

How many intertidal pits do they dig?How many intertidal pits do they dig?

About 185 dives/otter/dayAbout 7% of foraging intertidalEquals about 13 intertidal dives/dIf each pit takes 4 dives = 3 pits/dEquals about 1,100 pits/year for the “average” sea otterAssuming 50 otters at N. Knight

Equals about 55,000 intertidal pits/year

AqAqPuPu

SiSiPiW

hChChReW

hLbWhLbLbGoWh

OrOr

WhWhYeY

eChWhReR

e

# of

inte

rtid

al d

ives

/day

0

10

20

30

40

50

60

Females Males

Individual variation in intertidal foraging by sea otters

Results in <100 to 4,400 pits/yrper individual

Molecules of CYP1A mRNA/ng RNA

<55 < 10

10 < 15

15 < 20

20 < 25

25 < 30

30 < 35

35 < 40

40 < 45

45 < 50> 50

% o

f sea

otte

rs

0

10

20

30

40

90

100

Unoiled area (n=86)

Oiled area (n=71)

50

40

30

20

10

01996 1997 1998 2001

oiled unoiled

P450

1A

(mol

ecul

es o

f CY

P1A

mR

NA

x 1

06/ 1

00 n

g R

NA

) Cytochrome P4501A in Sea OttersCytochrome P4501A in Sea Otters

from unoiled and oiled Areasfrom unoiled and oiled Areas

CYP1A content in sea otters from oiled and unoiled areas: 2003*

0

2

4

6

8

10

12

14

16

18

O iled 2003 Unoiled 2002

CY

P1A

cps

* Preliminary results

Harlequin ducks: Exposure and Survival9

OiledUnoiled

10.0% 6.9% 2.2% 2.8%

8

P450

Sca

led

Inde

x 76543210

1998 2000 2001 2002

2004 sampling for P4502004 sampling for P450’’ssamong intertidal specialistsamong intertidal specialists

Sea OttersSea OttersHarlequin and Goldeneye DucksHarlequin and Goldeneye DucksPigeon Guillemots Pigeon Guillemots Black Oystercatchers Black Oystercatchers Masked GreenlingMasked GreenlingCrescent GunnelsCrescent Gunnels

Intertidal Ecosystem Cascade

1989

Bare rock

1990

Filamentous Algae

2000

1992 Fucus settlementOn barnacles

Fucus/barnacle mortality

Fucus recovery

1991

Barnacle settlement

Revising paradigmsRevising paradigmsOld New

Laboratory toxicologyLaboratory toxicologyRapid dispersalRapid dispersalShortShort--term toxicityterm toxicityAcute mortality Acute mortality dominantdominant

Direct effects only

EcotoxicologyEcotoxicologyPotential persistencePotential persistenceLongLong--term toxicityterm toxicityChronic effects Chronic effects significant with significant with multiple pathwaysmultiple pathwaysCleanClean--up and up and ecological cascades ecological cascades extend injury

Direct effects only

extend injury

Thank you for your attention!Thank you for your attention!