Eastern oyster settlement and early Eastern oyster settlement and early survival on alternative reef substrates survival on alternative reef substrates

adjacent to intertidal marsh, rip rap, and adjacent to intertidal marsh, rip rap, and manmade oyster reef habitats in manmade oyster reef habitats in

Lynnhaven Bay, VirginiaLynnhaven Bay, Virginia

R. Burke*, R. Lipcius, M. Luckenbach, R. Burke*, R. Lipcius, M. Luckenbach, P.G. Ross, J. Woodward, and D. SchulteP.G. Ross, J. Woodward, and D. Schulte

  ICSR CharlestonICSR Charleston11/17/0611/17/06

AcknowledgementsAcknowledgements

US Army Corp of Engineers - Norfolk District: US Army Corp of Engineers - Norfolk District: for providing funding and field supportfor providing funding and field support

VIMS Eastern Shore Field Crew: VIMS Eastern Shore Field Crew: for transport and assistance in deployment of >100 cages in for transport and assistance in deployment of >100 cages in the midst of a hectic schedulethe midst of a hectic schedule

Homeowners on Long Creek and First Landing State Park: for Homeowners on Long Creek and First Landing State Park: for permission to place cages and have land access to them.permission to place cages and have land access to them.

Special thanks to the entire Marine Conservation Biology Special thanks to the entire Marine Conservation Biology group at VIMS for their field support.group at VIMS for their field support.

Native Oyster Restoration – Native Oyster Restoration – Lynnhaven RiverLynnhaven River

US ACoE’s Investment:US ACoE’s Investment:An estimated $6.59 millionAn estimated $6.59 million““. . .restore up to 111.3 acres of oyster habitat . . .restore up to 111.3 acres of oyster habitat (which could be constructed out of shells (which could be constructed out of shells and/or and/or alternative materialsalternative materials) and by Year 5 are ) and by Year 5 are predicted to have an associated oyster biomass predicted to have an associated oyster biomass of approximately 130,000 kilograms (kg) on the of approximately 130,000 kilograms (kg) on the restored habitat alone.”restored habitat alone.”– Final Decision Document Amendment, Section 704B Final Decision Document Amendment, Section 704B

as Amended, Chesapeake Bay Oyster Recovery as Amended, Chesapeake Bay Oyster Recovery Phase IV, Lynnhaven River, Virginia (November 2005)Phase IV, Lynnhaven River, Virginia (November 2005)

VIMS’ RoleVIMS’ Role

Pre-Deployment:Pre-Deployment:

Plan DevelopmentPlan Development

Estimating oyster density Estimating oyster density across the variety of across the variety of habitats/substrateshabitats/substrates

Reef:Reef:– Site SelectionSite Selection– Composition (Shell and/or Composition (Shell and/or

some alternative)some alternative)

Oyster Disease Prevalence Oyster Disease Prevalence and Burdenand Burden

Oyster Genetic Oyster Genetic Make-up/DiversityMake-up/Diversity

Post-Deployment:Post-Deployment:Monitoring of Oyster:Monitoring of Oyster:

– SurvivalSurvival– SettlementSettlement– RecruitmentRecruitment– GrowthGrowth– Disease Prevalence Disease Prevalence

and Burdenand Burden– Genetic Genetic

Make-up/DiversityMake-up/Diversity

VIMS serves an advisory role to the ACoE in:VIMS serves an advisory role to the ACoE in:

Relevance of ResearchRelevance of Research

Production of experimental oyster Production of experimental oyster recruitment, and survival on loose shells recruitment, and survival on loose shells and different size classes of granite, and different size classes of granite, limestone marl, and concrete at different limestone marl, and concrete at different depths in the intertidal zone provides the depths in the intertidal zone provides the ACoE with system-specific information ACoE with system-specific information regarding which substrates are suitable regarding which substrates are suitable amongst the suite of available options.amongst the suite of available options.

Alternative Oyster Reefs: Rip-RapAlternative Oyster Reefs: Rip-Rap

Shell Heigth (mm)

Frequency

117.097.578.058.539.019.50.0

120

100

80

60

40

20

0

Histogram of LB RipRap

Average Broad Bay Oyster Density

770 oysters per m2

95 % CI: 729-811 oysters per m2

Shell Height (mm)

Chesapeake BayChesapeake Bay

Lynnhaven River System

**Provided by PG Ross**

Long Creek ExperimentLong Creek Experiment

Oyster Reef SiteNatural Marsh Site

Rip Rap Site 2

(Concrete)

Rip Rap Site 1 (Granite)

Granite (Lg/Sm)

Limestone Marl (Lg/Sm)Oyster Shell

Demolished Concrete

Experimental DesignExperimental Design

Fixed FactorsFixed Factors– Intertidal ZoneIntertidal Zone

Lower: Natural MarshLower: Natural Marsh

Middle: Rip Rap (Granite Middle: Rip Rap (Granite

and and Concrete)Concrete)

Upper: Restored Oyster Upper: Restored Oyster

ReefReef

– Caged/UncagedCaged/Uncaged– Substrate TypeSubstrate Type

36 Treatments x 3 36 Treatments x 3 replicates = 108 Traysreplicates = 108 Trays

SubstratesSubstrates– OSUOSU - Oyster Shell - Oyster Shell

UnconsolidatedUnconsolidated (from (from Long Creek Restored Long Creek Restored Oyster Reef)Oyster Reef)

– CVSCVS - Demolished - Demolished Concrete Concrete ((very smallvery small))

– GLGL - Granite - Granite ( (LargeLarge))

– GSGS - Granite - Granite ( (SmallSmall))

– LMLLML - Limestone Marl - Limestone Marl ((LargeLarge))

– LMSLMS - Limestone Marl - Limestone Marl ((SmallSmall))*Materials and Cages Provided by *Materials and Cages Provided by

Dr. Mark Luckenbach and PG RossDr. Mark Luckenbach and PG Ross

Sampling RegimeSampling RegimeDeployed: Deployed: – Late August 2005Late August 2005

Sampling RegimeSampling Regime– Late Fall 2005 Late Fall 2005

Post-RecruitmentPost-Recruitment

– Late Spring 2006Late Spring 2006Pre-RecruitmentPre-Recruitment

– Late Fall 2006Late Fall 2006Post-Recruitment (Ongoing)Post-Recruitment (Ongoing)

Non-Destructive SamplingNon-Destructive Sampling– On-site sampling of ¼ (1 On-site sampling of ¼ (1

quadrant) of each 0.25 sq m quadrant) of each 0.25 sq m replicate and return it to its replicate and return it to its original depth/locationoriginal depth/location

MonitorMonitor– Spat settlementSpat settlement– GrowthGrowth

Shell Height measured for Shell Height measured for a subset of samples (36)a subset of samples (36)

– SurvivalSurvival– Fouling Fouling – Presence/Absence of: Presence/Absence of:

Mud crabsMud crabsBlue CrabsBlue CrabsReef fishesReef fishesBryozoans, Sponges,Bryozoans, Sponges,Algae, etc.Algae, etc.

Hypothesis #1Hypothesis #1

HHoo::Spat survivalSpat survival will will not significantly differnot significantly differ

across across different substratesdifferent substrates

– HHA1A1: Spat survival will be higher on substrates with : Spat survival will be higher on substrates with

higher fractal dimension higher fractal dimension

– HHA2A2: Spat survival will be higher on larger substrates : Spat survival will be higher on larger substrates

as larger interstitial spaces will not provide ample as larger interstitial spaces will not provide ample protection for mud crabs – one of the major predators protection for mud crabs – one of the major predators of small oyster spatof small oyster spat

245 mm

140 mm

Concrete Limestone Marl

Small

Medium

Large

IV=47.9%; FD=1.073

IV=52.5%; FD=1.051

IV=52.2%; FD=1.039

IV=53.4%; FD=1.126

IV=57.0%; FD=1.171

IV=64.5%; FD=1.159

Oyster Population Parameters

Alternative Substrate Experiment

Oyster Mortality-Interstitial Space

y = 526224 x -2.2699

R2 = 0.8948p = 0.0092

0

10

20

30

40

50

60

70

80

90

40 45 50 55 60 65 70

% Interstitial Space

% O

yste

r M

orta

lity

•Interstital Space•Surface Complexity

245 mm

140 mm

Hypothesis #2Hypothesis #2

HHoo::Spat survivalSpat survival in in Caged treatments Caged treatments will will not not significantly differsignificantly differ from from uncaged treatmentsuncaged treatments

– Due to the size of mud crabs, their tendency to find Due to the size of mud crabs, their tendency to find refuge in the crevices created by small substrates, and refuge in the crevices created by small substrates, and their territorial nature, the 1-inch mesh of the cages their territorial nature, the 1-inch mesh of the cages should not hinder their recruitment or migration into the should not hinder their recruitment or migration into the cages.cages.

– HHAA: Spat survival in cages may be significantly less than : Spat survival in cages may be significantly less than in uncaged treatments due to exclusion of larger mud in uncaged treatments due to exclusion of larger mud crab predators (i.e. large blue crabs, predatory fish)crab predators (i.e. large blue crabs, predatory fish)

Hypothesis #3Hypothesis #3

HHoo::Spat recruitment and survivalSpat recruitment and survival will will not not

significantly differsignificantly differ between the Lower, Mid, between the Lower, Mid, and Upper Intertidal Zones.and Upper Intertidal Zones.– HHAA: Oyster spat recruitment and survival may : Oyster spat recruitment and survival may

be highest in the lower intertidal and lowest in be highest in the lower intertidal and lowest in the upper intertidal (Bartol and Mann, 2001).the upper intertidal (Bartol and Mann, 2001).

Substrate Type

CVS GL GS LML LMS OSU

Me

an

Liv

e S

pa

t

0

10

20

30

40

50

60

Fall 2005 ResultsFall 2005 Results

Substrate TypeSubstrate Type Oyster Spat Density +/- SEOyster Spat Density +/- SE

Concrete – Very Small (CVS)Concrete – Very Small (CVS) 284 +/- 99284 +/- 99Granite Large (GL)Granite Large (GL) 747 +/- 119747 +/- 119Granite Small (GS)Granite Small (GS) 781 +/- 141781 +/- 141

Limestone Marl Large (LML)Limestone Marl Large (LML) 144 +/- 42144 +/- 42Limestone Marl Small (LMS)Limestone Marl Small (LMS) 143 +/- 42143 +/- 42

Oyster Shell Unconsolidated (OSU)Oyster Shell Unconsolidated (OSU) 316 +/- 89316 +/- 89

Treatment

MC

-CV

SM

C-G

LM

C-G

SM

C-L

ML

MC

-LM

SM

C-O

SU

MU

-CV

SM

U-G

LM

U-G

SM

U-L

ML

MU

-LM

SM

U-O

SU

RR

U-C

VS

RR

U-G

LR

RU

-GS

RR

U-L

ML

RR

U-L

MS

RR

U-O

SU

RR

C-C

VS

RR

C-G

LR

RC

-GS

RR

C-L

ML

RR

C-L

MS

RR

C-O

SU

OR

U-C

VS

OR

U-G

LO

RU

-GS

OR

U-L

ML

OR

U-L

MS

OR

U-O

SU

OR

C-C

VS

OR

C-G

LO

RC

-GS

OR

C-L

ML

OR

C-L

MS

OR

C-O

SU

Me

an

Liv

e S

pa

t

0

20

40

60

80

100

120

Statistical AnalysisStatistical Analysis

Two-way ANOVA (substrate & cage control) Two-way ANOVA (substrate & cage control) for the following response variables:for the following response variables: – Count of Live Spat per sample (1/16Count of Live Spat per sample (1/16 thth m m22))– Proportion of Live Spat per sample (1/16Proportion of Live Spat per sample (1/16 thth m m22))– Exterior Live Spat per sample (1/16Exterior Live Spat per sample (1/16 thth m m22))– Interior Live Spat per sample (1/16Interior Live Spat per sample (1/16 thth m m22))

Three-Way ANOVA (including Intertidal Zone) for the Three-Way ANOVA (including Intertidal Zone) for the same response variables as the Two-ANOVAs.same response variables as the Two-ANOVAs.

Student’s t-test to distinguish any handling effectsStudent’s t-test to distinguish any handling effects

Lower IntertidalLower Intertidal

Mid IntertidalMid Intertidal

Upper IntertidalUpper Intertidal

Across the Intertidal ZoneAcross the Intertidal Zone

ConclusionsConclusions

““Substrate Matters”Substrate Matters”– Granite (Lg or Sm) may be a favorable oyster reef Granite (Lg or Sm) may be a favorable oyster reef

construction material, since it had significantly higher construction material, since it had significantly higher recruitment and, on average, the highest proportion of recruitment and, on average, the highest proportion of live oysters amongst the different substrate typeslive oysters amongst the different substrate types

Caging negatively impacted oyster survival Caging negatively impacted oyster survival especially on the granite treatments:especially on the granite treatments:– The large difference of means for caged v. uncaged trays The large difference of means for caged v. uncaged trays

of granite indicates a higher susceptibility of oyster spat of granite indicates a higher susceptibility of oyster spat on this substrate upon an apparent relaxation of on this substrate upon an apparent relaxation of predation on small predators, such as mud crabs, predation on small predators, such as mud crabs, provided by the caged controls.provided by the caged controls.

ConclusionsConclusions

Intertidal Zone significantly influenced Intertidal Zone significantly influenced recruitment: Lower > Mid > Upperrecruitment: Lower > Mid > UpperExterior Live Spat Count > Interior Live Spat Exterior Live Spat Count > Interior Live Spat Count (Edge effects)Count (Edge effects)Interiors of trays were not negatively impacted Interiors of trays were not negatively impacted by caging.by caging.Although there was significant mortality from the Although there was significant mortality from the Fall to the Spring in quadrant #1 (Paired t-test), Fall to the Spring in quadrant #1 (Paired t-test), 2-sample t-tests for each substrate type 2-sample t-tests for each substrate type revealed no significant handling effect.revealed no significant handling effect.

Questions?

Thank YouThank You