Long-term Ecosystem Responses to the Exxon Valdez oil spill

Transcription

1 Long-term Ecosystem Responses to the Exxon Valdez oil spill J.L Bodkin, C.H. Peterson, S.D Rice, J.W. Short, D.E. Esler,, B.E. Ballachey, D.B. Irons Science 2003 v 302 :

2 Outline The setting, the spill, acute effects and assumptions Shoreline/damage assessments Population assessments Delayed recoveries; why? Lingering oil and routes of exposure Ecological cascades Revising oil pollution risk assessment

3 PRINCE WILLIAM SOUND

4 Two Marine Ecosystem Components Nearshore Offshore Nearshore Macroalgae-driven Benthic inverts pathway Space limited Substrate important Depth limits LINKS Nutrient exchange Egg/larvae/juvenile transport Migration/life cycles DISTINCTIONS Offshore Phytoplankton-driven Zoo/Fish pathway Nutrient limited Light limited Extreme depths

5 Offshore Web

6 Nearshore Web

7 Exxon Valdez Oil Spill 42 million liters of crude oil spilled March 24, 1989

8 Kenai Pen. Alaska Prince William Sound Gulf of Alaska 100 Miles Kodiak Is Alaska Peninsula

9 The Exxon Valdez Oil Spill Then and Now

10 - Conventional assumptions about effects of oil pollution on wildlife populations: - direct, acute effects are most important 250,000 dead seabirds, 3,000 dead sea otters

11 - Conventional assumptions about effects of oil pollution on wildlife populations: - direct, acute effects are most important - oil is removed quickly by natural processes

12 - Conventional assumptions about effects of oil pollution on wildlife populations: - direct, acute effects are most important - oil is removed quickly by natural processes - therefore, long-term chronic oil exposure is not a problem, and affected populations should rebound from acute mortalities in a short period of time (months to a few years) Not Necessarily

13 Shoreline and Clean up and Damage Assessment assessments of oiled shorelines

14 Shoreline Assessment Results: 1989: 2,000 km of oiled beach 1992: 11 km of oiled beach, 1.15 ha subsurface oil (2.8 ac) 1992 Shoreline Assessment Conclusions: Oil mostly in upper intertidal Oil rapidly dispersing

15 Oil on PWS Beaches: (Actual and Projected) Amount Remaining (m^3) Post Spill Projected But some injured species are not recovering, why? Year

16 1995 Nearshore Vertebrate Predators

17 1995 NVP Approach Select top level nearshore predators that represent: Birds and mammals Invertebrate and fish trophic pathways, and Sample all populations in oiled and unoiled areas (limited inference)

18 Study Areas

19 Types of Data Have they recovered? - Population density - Birth and survival - Health and condition Is it food? - Prey abundance - Predator condition - Prey consumption Is it demography? - Population models Is it oil? - CYP1A - Blood chemistry - Hematology

20 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

21 HARLEQUIN DUCK POPULATION TRENDS ADFG Fall Surveys E. Prince William Sound (Unoiled) W. Prince William Sound (Oiled)

22 Adult Female Harlequin Duck Survival Winters , , and Survival Probability Unoiled Oiled Early Winter Mid Winter Late Winter October November December January February March Week

23 Is it Food? No difference in abundance of food at oiled and unoiled sites Food does not explain a significant amount of variation in duck abundance above that explained by other habitat variables

24 Is it Oil? Average (+( 95% CI) Cytochrome P450 1A Induction in Harlequin Ducks - Winter 1998 EROD Activity (pmol/min/mg) Main Bay and Crafton Island (Oiled) Area Montague Island (Unoiled)

25 Sea Otter Recovery as of Minimum prespill Knight Island population size in 1989 (from Dean et al. 2000) Estimated population size Heavily oiled Knight Island Year

26 What can carcasses tell us about survival?

27 Trends in Sea Otter Mortality in WPWS, as represented by the ages of animals dying each year spill year Proportion prime-age dying Pre-spill Post-spill Year Monson et al. 2002

28 Sea otter population trends and predicted trajectories based on estimated survival rates WPWS 1.2 Proportion Northern Knight Is Year Monson et al. 2000

29 Measures of Food Availability (all significantly > at oiled sites) oiled unoiled Consumption Foraging efficiency Condition (Kj/hr) (min/d) (g/cm) Dean et al. 2002

30 Is it Oil? Is it Oil? Oil exposure in WPWS sea otters, , indicated by P4501A Unoiled area (n=86) Oiled area (n=71) % of sea otters 10 <5 5 < < < < < < < < < 50 > 50 Molecules of CYP1A mrna/ng RNA

31 CYP1A Biomarker - Results from NVP Study Species Sea otters > > > Harlequin ducks > Barrow s s Goldeneyes Masked Greenlings > > > River otters > = = Pigeon guillemot chicks = Pigeon guillemot adults > (1999)

32 Nearshore Recovery Fish eaters River Pigeon Otter Guillemot Invert eaters Harlequin Sea Duck Otter Recovered? Yes No No No Is it food? _ Yes No No Is it oil? _ Possibly Yes Yes

33 NVP Conclusions (1999) SO/HADU share habits and habitats in the nearshore Elevated mortality constraining recovery Elevated biomarkers of oil exposure Accumulating evidence linking residual oil and continuing injury

34 So what is the source and route of exposure? Revisit shoreline assessment assumptions Revisit sampling intertidal sediments Continue monitoring exposure through biomarkers Investigate pathways of potential exposure

35 EL056A EL056C Site Photo 2001 Shoreline survey for residual EVOS oil Oil residue in pit

36 Stratified Random Sampling Grid +4.6m 1/2 meter drops A B C D E F G H m 12.5m 100 m 96 randomly selected pit locations Total # random pits = 6,775

37 LOR MOR 2001 Subsurface Oil - Light Oil Residue Moderate Oil Residue Heavy Oil Residue HOR

38 Intertidal Subsurface Oil 2001 survey (+6ft) +16ft - 0ft Majority of Subsurface oil (+8.2ft 3.3ft) Oil

39 2001 Sampled 91 sites Results 53 sites with oil 38 sites without

40 Estimated Oiled Area 2001 Surface Oil: 4.13 ha ( ha) Subsurface Oil: 7.80 ha ( ha) Total: 11.3 ha ( ha) 1992 estimate = 1.5 ha of subsurface oil

41 Oil on PWS Beaches: (Projected vs Actual) Amount Remaining (m^3) Post Spill 2001 ABL Year

42 Conclusions Oil more persistent than anticipated Intertidal biological zone more affected than anticipated Little long-term impact on subtidal

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

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

45 Known Diet of Sea Otters at Knight Island Based on Visual Observations in 2002 (N = 459) 80 Frequency of Occurrence (%) clam mussel bivalve crab urchin stars other

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49 Time Depth Recorder Implants 2003 and Depth (m) Time (hrs)

50 How many intertidal pits do they dig? About 185 dives/otter/day About 7% of foraging intertidal Equals about 13 intertidal dives/d If each pit takes 4 dives = 3 pits/d Equals about 1,100 pits/year for the average sea otter Assuming 50 otters at N. Knight Equals about 55,000 intertidal pits/year

51 Individual variation in intertidal foraging by sea otters Results in <100 to 4,400 pits/yr per individual # of intertidal dives/day % of sea otters 10 0 Molecules of CYP1A mrna/ng RNA Unoiled area (n=86) Oiled area (n=71) <5 5 < < < < < < < < < 50 > AqAq PuPu SiSi PiWh ChCh ReWh LbWh LbLb GoWh OrOr WhWh YeYe ChWh 0 ReRe Females Males

52 P450 1A (molecules of CYP1A mrna x 10 6 / 100 ng RNA) Cytochrome P4501A in Sea Otters from unoiled and oiled Areas unoiled oiled

53 CYP1A content in sea otters from oiled and unoiled areas: 2003* CYP1A cps Oiled 2003 Unoiled 2002 * Preliminary results

54 Harlequin ducks: Exposure and Survival P450 Scaled Index Oiled Unoiled 10.0% 6.9% 2.2% 2.8%

55 2004 sampling for P450 s among intertidal specialists Sea Otters Harlequin and Goldeneye Ducks Pigeon Guillemots Black Oystercatchers Masked Greenling Crescent Gunnels

56 Intertidal Ecosystem Cascade 1989 Bare rock 1990 Filamentous Algae

57 1991 Barnacle settlement Fucus recovery 2000 Fucus/barnacle mortality 1992 Fucus settlement On barnacles

58 Revising paradigms Old Laboratory toxicology Rapid dispersal Short-term term toxicity Acute mortality dominant Direct effects only New Ecotoxicology Potential persistence Long-term toxicity Chronic effects significant with multiple pathways Clean-up and ecological cascades extend injury

59 Thank you for your attention!