Assessment of Bivalve Recovery on Treated Mixed-Soft Beaches in

Western Prince William Sound

Assessment of Bivalve Recovery on Treated Mixed-Soft Beaches in

Western Prince William Sound

Dennis C. LeesLittoral Ecological & Environmental

Services

William B. Driskell

22 January 2006

Dennis C. LeesLittoral Ecological & Environmental

Services

William B. Driskell

22 January 2006 Funded by the Exxon Valdez Oil Spill Trustee Council

• Short HistoryShort History– NOAA Shoreline Treatment Effects Study - 1990-96NOAA Shoreline Treatment Effects Study - 1990-96– Infaunal data from geographically limited studies Infaunal data from geographically limited studies

indicated negative effects at Treated sites:indicated negative effects at Treated sites:• Sediment EffectsSediment Effects• Impoverished infaunal assemblages, esp. long-lived clamsImpoverished infaunal assemblages, esp. long-lived clams• Time-series data suggested recovery was very slowTime-series data suggested recovery was very slow

• Objectives of this study:Objectives of this study:– Assess persistence of depressed condition of clam Assess persistence of depressed condition of clam

assemblages in mixed-soft sediments at Treated assemblages in mixed-soft sediments at Treated sitessites

– Assess relationship between sediment Assess relationship between sediment characteristics and depressed condition of clam characteristics and depressed condition of clam assemblages in mixed-soft sediments.assemblages in mixed-soft sediments.

Alternative HypothesesAlternative HypothesesAlternative HypothesesAlternative Hypotheses

Sediments -- Coarser and concentrations of organic matter are depressed at Treated sites.

N, S, and H’ -- Higher at Reference sites except for N in infaunal samples.

Short-lived, nestling, pioneering species -- More at Treated sites in infaunal samples.

All large clams -- Fewer at Treated sites

Sediments -- Coarser and concentrations of organic matter are depressed at Treated sites.

N, S, and H’ -- Higher at Reference sites except for N in infaunal samples.

Short-lived, nestling, pioneering species -- More at Treated sites in infaunal samples.

All large clams -- Fewer at Treated sites

Sampling Design & Sampling Design & MethodsMethods

Sampling Design & Sampling Design & MethodsMethods

40 sites - 36 Random & 4 Historic Sites 16 Oiled but Unwashed (Reference) sites and 20

Oiled and Washed (Treated) sites 4 Old NOAA sites to assess consistency from

earlier study

At Each Site Five 10-cm core samples for clams and infauna Three 1/16 m2 excavation samples for larger clams 1 composite sediment sample for grain size, TOC

& TKN

40 sites - 36 Random & 4 Historic Sites 16 Oiled but Unwashed (Reference) sites and 20

Oiled and Washed (Treated) sites 4 Old NOAA sites to assess consistency from

earlier study

At Each Site Five 10-cm core samples for clams and infauna Three 1/16 m2 excavation samples for larger clams 1 composite sediment sample for grain size, TOC

& TKN

SL01SL01

KN554BKN554B

KN554BKN554B

Sampling

Locations

Sampling

Locations

Typical Pocket Beaches

Typical Pocket Beaches

CH08CH08

KN130BKN130B

Common Clams in Common Clams in ExcavationsExcavations

Common Clams in Common Clams in ExcavationsExcavations

Common Clams in Common Clams in ExcavationsExcavations

Common Clams in Common Clams in ExcavationsExcavations

ProtothacProtothacaaProtothacProtothacaa

SaxidomusSaxidomusSaxidomusSaxidomusMacomasMacomasMacomasMacomas

HiatellaHiatellaHiatellaHiatella

DiplodontDiplodontaaDiplodontDiplodontaa

Papermate sp.Papermate sp.Papermate sp.Papermate sp.

Comparison of Sediment Comparison of Sediment CharacteristicsCharacteristics

Comparison of Sediment Comparison of Sediment CharacteristicsCharacteristics

† † Significant difference (p = 0.028)Significant difference (p = 0.028)

SedimentSedimentVariableVariable

ReferencReferencee TreatedTreated Old NOAAOld NOAA

PGS (mm)PGS (mm)†† 6.8 ± 0.76.8 ± 0.710.3 ± 10.3 ±

1.61.6 12.7 ± 3.112.7 ± 3.1

Silt/Clay (%)Silt/Clay (%) 3.1 ± 0.33.1 ± 0.3 2.9 ± 0.42.9 ± 0.4 2.1 ± 0.32.1 ± 0.3

TOC (%)TOC (%) 1.1 ± 0.21.1 ± 0.2 1.2 ± 0.21.2 ± 0.2 0.7 ± 0.20.7 ± 0.2

TKN (mg/Kg)TKN (mg/Kg) 486 ± 72486 ± 72 456 ± 57456 ± 57 204 ± 74204 ± 74

Numerical Characteristics for Numerical Characteristics for Infaunal SamplesInfaunal Samples

Numerical Characteristics for Numerical Characteristics for Infaunal SamplesInfaunal Samples

NumericNumerical al

Variable Variable

AlternativAlternative e

HypothesiHypothesiss

ReferencReferencee TreatedTreated

ExacExact pt p

No. of No. of Indiv. Indiv. (N)(N)

Treat > Treat > RefRef 51 ± 6051 ± 60 78 ± 9478 ± 94 0.170.17

No. of No. of Spp. (S)Spp. (S)

Ref > Ref > TreatTreat 4.9± 2.34.9± 2.3

4.2 ± 4.2 ± 2.42.4 0.210.21

ShannonShannon-Wiener -Wiener

H’H’Ref > Ref > TreatTreat 1.1 ± 0.41.1 ± 0.4

0.6 ± 0.6 ± 0.50.5

0.000.0033

Numerical Characteristics for Numerical Characteristics for Excavation SamplesExcavation Samples

Numerical Characteristics for Numerical Characteristics for Excavation SamplesExcavation Samples

NumericNumerical al

Variable Variable

AlternativAlternative e

HypothesiHypothesiss

ReferencReferencee TreatedTreated

ExacExact pt p

NNRef > Ref > TreatTreat 65 ± 7565 ± 75 23 ± 2423 ± 24

0.010.0122

SSRef > Ref > TreatTreat

3.4 ± 3.4 ± 1.61.6

2.5 2.5 ±1.3±1.3

0.070.0755

ShannonShannon-Wiener -Wiener

H’H’Ref > Ref > TreatTreat

0.6 ± 0.6 ± 0.40.4

0.5 ± 0.5 ± 0.40.4 0.20.2

Species CompositionSpecies CompositionSpecies CompositionSpecies CompositionSpecies composition was similar in Infaunal and Species composition was similar in Infaunal and Excavation samples and, generally, at Reference and Excavation samples and, generally, at Reference and Treated sites.Treated sites.

Six most abundant species in overall order of abundance Six most abundant species in overall order of abundance by sample type -- four species in common.by sample type -- four species in common.

InfaunaInfauna ExcavationExcavationRochefortia - TinyRochefortia - Tiny Littleneck clamLittleneck clamArctic nestling clamArctic nestling clam Arctic Nestling clamArctic Nestling clamLittleneck clamLittleneck clam Pointed macomaPointed macomaNorthern horsemusselNorthern horsemussel Butter clamButter clamBaltic macomaBaltic macoma DiplodontaDiplodontaButter clamButter clam Baltic macomaBaltic macoma

Species composition was similar in Infaunal and Species composition was similar in Infaunal and Excavation samples and, generally, at Reference and Excavation samples and, generally, at Reference and Treated sites.Treated sites.

Six most abundant species in overall order of abundance Six most abundant species in overall order of abundance by sample type -- four species in common.by sample type -- four species in common.

InfaunaInfauna ExcavationExcavationRochefortia - TinyRochefortia - Tiny Littleneck clamLittleneck clamArctic nestling clamArctic nestling clam Arctic Nestling clamArctic Nestling clamLittleneck clamLittleneck clam Pointed macomaPointed macomaNorthern horsemusselNorthern horsemussel Butter clamButter clamBaltic macomaBaltic macoma DiplodontaDiplodontaButter clamButter clam Baltic macomaBaltic macoma

Mean Number per mMean Number per m22 of of Clams in Infaunal Clams in Infaunal

Samples*Samples*

Mean Number per mMean Number per m22 of of Clams in Infaunal Clams in Infaunal

Samples*Samples*

SpeciesSpeciesReferencReferenc

ee TreatedTreated

RochefortiaRochefortia†††† 25332533 58545854

Arctic nestling Arctic nestling clamclam 10121012 14041404

Littleneck clamLittleneck clam†† 13061306 771771

Butter clamButter clam†††††† 189189 6767*Small species or juveniles of larger species, *Small species or juveniles of larger species, †† p < 0.2 p < 0.2 – – Longevity < 10 years, Longevity < 10 years, †††† p < 0.1 p < 0.1 – – Longevity > 15 years, Longevity > 15 years, †††††† p < 0.01 p < 0.01

Comparison of Pioneer and Comparison of Pioneer and Long-lived Infaunal Clams*Long-lived Infaunal Clams*Comparison of Pioneer and Comparison of Pioneer and Long-lived Infaunal Clams*Long-lived Infaunal Clams*

TypeTypeRef Ref

(no./ m(no./ m22))Treated Treated (no./m(no./m22))

T/R T/R RatioRatio

PioneerPioneer 35453545 72587258 210%210%

Long-livedLong-lived 14951495 838838 60%60%

Pioneer/Long-Pioneer/Long-lived Ratiolived Ratio 2.42.4 8.78.7 370%370%

*Small species or juveniles of larger species*Small species or juveniles of larger species– – Longevity < 10 years, surface nestlersLongevity < 10 years, surface nestlers– – Longevity > 15 years, deep burrowersLongevity > 15 years, deep burrowers

Mean Number per mMean Number per m22 of of Clams in Excavation Clams in Excavation

Samples*Samples*

Mean Number per mMean Number per m22 of of Clams in Excavation Clams in Excavation

Samples*Samples*SpeciesSpecies ReferenceReference TreatedTreated

Nestling clamNestling clam†† 308308 164164

Littleneck clamLittleneck clam†††††† 551551 341341

Butter clamButter clam†††† 7979 5555*Small species or juveniles of larger species*Small species or juveniles of larger species– – Longevity < 10 years, surface nestlersLongevity < 10 years, surface nestlers– – Longevity > 15 years, deep burrowersLongevity > 15 years, deep burrowers

Comparison of Pioneer & Comparison of Pioneer & Long-lived Clams in Long-lived Clams in Excavation SamplesExcavation Samples

Comparison of Pioneer & Comparison of Pioneer & Long-lived Clams in Long-lived Clams in Excavation SamplesExcavation Samples

SpeciesSpeciesRefRef

(no./ m (no./ m22))

TreatedTreated (no./ (no./ mm22))

T/RT/RRatioRatio

PioneersPioneers 308308 164164 53%53%

Long-livedLong-lived 630630 396396 63%63%

Pioneer/Pioneer/Long-lived Long-lived

RatioRatio 0.490.49 0.410.41 84%84%*Larger size fraction*Larger size fraction– – Longevity < 10 years, surface nestlersLongevity < 10 years, surface nestlers– – Longevity > 15 years, deep burrowersLongevity > 15 years, deep burrowers

Functional Ramifications of Functional Ramifications of Treatment EffectsTreatment Effects

Functional Ramifications of Functional Ramifications of Treatment EffectsTreatment Effects

Large long-lived clams are important Large long-lived clams are important prey items for sea otters.prey items for sea otters.

Excavation samples provide a better Excavation samples provide a better representation of prey-sized clams.representation of prey-sized clams.

Large long-lived clams in excavations Large long-lived clams in excavations were 40% less abundant at Treated were 40% less abundant at Treated sites.sites.

Ergo, Treated sites are considerably less capable of supporting sea otters.

Large long-lived clams are important Large long-lived clams are important prey items for sea otters.prey items for sea otters.

Excavation samples provide a better Excavation samples provide a better representation of prey-sized clams.representation of prey-sized clams.

Large long-lived clams in excavations Large long-lived clams in excavations were 40% less abundant at Treated were 40% less abundant at Treated sites.sites.

Ergo, Treated sites are considerably less capable of supporting sea otters.

ConclusionsConclusionsConclusionsConclusionsAs predictedAs predicted

Sediments at Treated sites -- Coarser than at Reference Sediments at Treated sites -- Coarser than at Reference sites.sites.

INFAUNAINFAUNA H’ was significantly higher at Reference sites and S H’ was significantly higher at Reference sites and S

exhibited strong similar trends.exhibited strong similar trends. As predicted, N was higher at Treated sites.As predicted, N was higher at Treated sites. Numerically, small nestling pioneer species dominated Numerically, small nestling pioneer species dominated

species composition at both Treated and Reference sites.species composition at both Treated and Reference sites. Importance of long-lived species was lower at Treated Importance of long-lived species was lower at Treated

sites.sites. Density of pioneer species was >2 times higher than Density of pioneer species was >2 times higher than

long-lived species at Reference sites but >8.5 times long-lived species at Reference sites but >8.5 times higher at Treated sites.higher at Treated sites.

As predictedAs predicted Sediments at Treated sites -- Coarser than at Reference Sediments at Treated sites -- Coarser than at Reference

sites.sites.

INFAUNAINFAUNA H’ was significantly higher at Reference sites and S H’ was significantly higher at Reference sites and S

exhibited strong similar trends.exhibited strong similar trends. As predicted, N was higher at Treated sites.As predicted, N was higher at Treated sites. Numerically, small nestling pioneer species dominated Numerically, small nestling pioneer species dominated

species composition at both Treated and Reference sites.species composition at both Treated and Reference sites. Importance of long-lived species was lower at Treated Importance of long-lived species was lower at Treated

sites.sites. Density of pioneer species was >2 times higher than Density of pioneer species was >2 times higher than

long-lived species at Reference sites but >8.5 times long-lived species at Reference sites but >8.5 times higher at Treated sites.higher at Treated sites.

ConclusionsConclusionsConclusionsConclusionsEXCAVATION SAMPLESEXCAVATION SAMPLES

Numerical characteristics were depressed at Numerical characteristics were depressed at Treated sites.Treated sites.

Density of both long-lived burrowing clams Density of both long-lived burrowing clams and nestling pioneer species was depressed at and nestling pioneer species was depressed at Treated sites.Treated sites.

Because treatment caused loss of larger Because treatment caused loss of larger individuals of both pioneering and long-lived individuals of both pioneering and long-lived species, abundance of both types of clams species, abundance of both types of clams was significantly lower at Treated sites than at was significantly lower at Treated sites than at Reference sites.Reference sites.

EXCAVATION SAMPLESEXCAVATION SAMPLES Numerical characteristics were depressed at Numerical characteristics were depressed at

Treated sites.Treated sites.

Density of both long-lived burrowing clams Density of both long-lived burrowing clams and nestling pioneer species was depressed at and nestling pioneer species was depressed at Treated sites.Treated sites.

Because treatment caused loss of larger Because treatment caused loss of larger individuals of both pioneering and long-lived individuals of both pioneering and long-lived species, abundance of both types of clams species, abundance of both types of clams was significantly lower at Treated sites than at was significantly lower at Treated sites than at Reference sites.Reference sites.

In SummaryIn SummaryIn SummaryIn SummarySites treated with HP/HW wash during the 1989-90 EVOS Sites treated with HP/HW wash during the 1989-90 EVOS cleanup still exhibited significant though subtle effects cleanup still exhibited significant though subtle effects from treatment in 2002.from treatment in 2002.

Sediment grain size -- Coarser at Treated sites.Sediment grain size -- Coarser at Treated sites. Numerical characteristics (N, S, H’) in infaunal and Numerical characteristics (N, S, H’) in infaunal and

excavation samples -- Generally lower at Treated sites.excavation samples -- Generally lower at Treated sites. Species composition -- Similar qualitatively but differed Species composition -- Similar qualitatively but differed

quantitatively.quantitatively. Functional aspects of the clam assemblages differed Functional aspects of the clam assemblages differed

markedly.markedly. Dominant species at Reference and Treated sites both Dominant species at Reference and Treated sites both

include larger, long-lived deep-burrowing clams.include larger, long-lived deep-burrowing clams. Because density of large clams is ~40% lower at Because density of large clams is ~40% lower at

Treated sites, they can support considerably fewer Treated sites, they can support considerably fewer large predators like sea otters than Reference large predators like sea otters than Reference sites.sites.

Sites treated with HP/HW wash during the 1989-90 EVOS Sites treated with HP/HW wash during the 1989-90 EVOS cleanup still exhibited significant though subtle effects cleanup still exhibited significant though subtle effects from treatment in 2002.from treatment in 2002.

Sediment grain size -- Coarser at Treated sites.Sediment grain size -- Coarser at Treated sites. Numerical characteristics (N, S, H’) in infaunal and Numerical characteristics (N, S, H’) in infaunal and

excavation samples -- Generally lower at Treated sites.excavation samples -- Generally lower at Treated sites. Species composition -- Similar qualitatively but differed Species composition -- Similar qualitatively but differed

quantitatively.quantitatively. Functional aspects of the clam assemblages differed Functional aspects of the clam assemblages differed

markedly.markedly. Dominant species at Reference and Treated sites both Dominant species at Reference and Treated sites both

include larger, long-lived deep-burrowing clams.include larger, long-lived deep-burrowing clams. Because density of large clams is ~40% lower at Because density of large clams is ~40% lower at

Treated sites, they can support considerably fewer Treated sites, they can support considerably fewer large predators like sea otters than Reference large predators like sea otters than Reference sites.sites.

AcknowledgementsAcknowledgements

Our sponsor, the EVOS Trustee CouncilOur sponsor, the EVOS Trustee Council

Ms. Carrie Holba at ARLISMs. Carrie Holba at ARLIS

Terry Kennedy and staff - Cordova AirTerry Kennedy and staff - Cordova Air

David and Annette Janka - R/V AukletDavid and Annette Janka - R/V Auklet

Dr. Jon Houghton - Pentec/Hart CrowserDr. Jon Houghton - Pentec/Hart Crowser

Dr. Alan Mearns & Gary Shigenaka - NOAADr. Alan Mearns & Gary Shigenaka - NOAA

Dr. Sarah Gerken - UAADr. Sarah Gerken - UAA

Kathleen LeesKathleen Lees