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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)
Long Creek ExperimentLong Creek Experiment
Oyster Reef SiteNatural Marsh Site
Rip Rap Site 2
(Concrete)
Rip Rap Site 1 (Granite)
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).
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
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.