Download Harwell, H. D. - South Carolina Sea Grant Consortium

Reef-associated fauna in Chesapeake Bay:
Does oyster species affect habitat function?
H. Harwell*1, P. Kingsley-Smith2, M. Kellogg3,
K. Paynter, Jr.3 and M. Luckenbach1.
1Virginia Institute of Marine
2South Carolina Department
3University
Science, The College of William & Mary
of Natural Resources,
of Maryland
Illustration by Kent Forrest, © VIMS
The Role of Habitat Complexity:
• Structurally complex habitats offer a greater variety of different
microhabitats and niches, allowing more species to co-exist and
contribute to within habitat diversity (Pianka 1988, Levin 1992).
• The importance of habitat heterogeneity / complexity has been
investigated in many marine systems, including coral reefs, seagrass
beds, rocky intertidal, mangroves, macroalgae, and oyster reefs.
Abundance
• Macroinvertebrate densities and species richness are generally
positively correlated with structural complexity (Crowder and
Cooper 1982, Diehl 1992).
Complexity
Does habitat complexity vary between oyster species?
C. sikamea
If so, how will these differences affect
habitat utilization?
C. ariakensis
C. virginica
C. ariakensis
Photo credits: Mark Luckenbach
Objectives
Compare the complexity of experimental C. ariakensis and
C. virginica reefs by examining vertical relief and surface
complexity.
Evaluate and compare the utilization of experimental C.
ariakensis and C. virginica reefs by other organisms.
Investigate the relationship between the development of
reef associated communities and habitat complexity.
Experimental Design
• 4 sites in Chesapeake Bay
• 4 experimental “reef” treatments
at each site:
- triploid C. virginica only
- triploid C. ariakensis only
- 50% C. v. & 50% C. a
- Shell only
• 2 replicates of each treatment per
site
• Treatments placed in cages for
biosecurity
• Each cage has a matrix of 5 x 5
trays
Delaware
Bay
SEVERN RIVER
Subtidal (3 - 4m)
Low salinity (3 - 14 mean daily psu)
Low predation pressure
Low Dermo / No MSX
PATUXENT RIVER
Subtidal (3 - 4m)
Low salinity (8 - 16 mean daily psu)
Moderate predation pressure
Low Dermo / No MSX
Chesapeake Bay
YORK RIVER
Subtidal (1 - 2m)
Mid salinity (9 - 21 mean daily psu)
High predation pressure
High Dermo / High MSX
Atlantic Ocean
MACHIPONGO RIVER
Intertidal
High salinity (5 -33 mean daily psu)
High predation pressure
High Dermo / Low MSX
Sampling Procedure
Quantifying Habitat Complexity
• maximum vertical height
• average ‘reef’ height (n = 10)
• surface rugosity index
Statistical Analysis
• 2-way ANOVA’s:
• Site and treatment effects on macrofaunal abundance,
biomass, species richness, species evenness, and ShannonWiener diversity.
• Indices of habitat complexity (maximum and average
vertical heights, surface rugosity) between sites and
treatments.
• Data were log transformed when necessary to meet
assumptions of normality and homogeneity of variance.
• Pair-wise comparisons were conducted via Tukey’s tests.
• Nonparametric multi-dimensional scaling (MDS) and Analysis of
Similarity (ANOSIM) to evaluate variations in community structure
between treatments.
80
C. virginica
C. ariakensis
60
Total number of live
oysters across all cages
Machipongo River, VA
July 5th 2006
40
20
80
C. virginica
C. ariakensis
York River, VA
July 24th 2006
60
Total number of live
oysters across all cages
40
20
80
C. virginica
C. ariakensis
60
Total number of live
oysters across all cages
Patuxent River, MD
July 10th 2006
40
20
80
C. virginica
C. ariakensis
60
Total number of live
oysters across all cages
Severn River, MD
July 17th 2006
40
20
0
30
60
Shell length (mm)
90
120
Severn
Height from top of tray (cm)
8
6
6
4
4
2
2
0
0
C. ariakensis
C. virginica
mixed
shell
York
8
C. ariakensis
6
4
4
2
2
0
C. virginica
mixed
shell
Machipongo
8
6
0
C. ariakensis
C. virginica
mixed
shell
maximum 'reef' height
Factor
Patuxent
8
F
p
C. ariakensis
C. virginica
mixed
shell
mean 'reef' height
Tukey Comparisons
Site
25.95 < 0.0001
46.32 <0.0001
YorkA, PatuxentA, SevernA, MachipongoB
PatuxentA, YorkA, SevernB, MachipongoC
Treatment
36.11 < 0.0001
68.29 < 0.0001
C.a.A, mixA, C.v.A, shellB
C.a.A, mixA, C.v.B, shellC
Site*Treatment
5.58
7.76
< 0.0001 Treatment effects driven by YR and PR sites
< 0.0001 Treatment effects driven by YR and PR sites
Habitat Complexity: Surface Rugosity
Severn (low salinity)
Surface rugosity Index
1.6
1.6
1.4
1.4
1.2
1.2
1
Patuxent (mid salinity)
1
C. ariakensis C. virginica
mixed
shell
York (high salinity)
1.6
C. ariakensis
1.6
1.4
1.4
1.2
1.2
1
C. virginica
mixed
shell
Machipongo (high salinity, intertidal)
1
C. ariakensis C. virginica
mixed
shell
C. ariakensis
C. virginica
mixed
shell
Factor
F
p
Tukey Comparisons
Site
21.46
< 0.0001
YorkA, SevernB, PatuxentB, MachipongoC
Treatment
29.54
< 0.0001
C.a.A, mixA, C.v.A, shellB
Site*Treatment
5.25
0.0003
Treatment effects most pronounced at York
Between-sites Comparison of Reef-associated Fauna
July 2006
Severn Patuxent
York
Machipongo
(low)
(mid)
(high)
(high, intertidal)
22
35
63
48
# of dominant taxa
Total # of associated
organisms
8
17,009
6
32,419
12
40,695
16
4,311
Total biomass of
associated fauna (g)
167.95
571.05
213.20
31.71
Total oyster biomass (g)
456.11
781.72
1371.05
22.59
# of species
Dominant Reef-associated Fauna
Severn (low salinity)
1
Species1 Richness: Lowest
Species Evenness:3 Intermediate
Diversity:
Lowest
York (high salinity)
Patuxent (mid salinity)
1
Species Richness: Intermediate
2
1
Species Evenness: Lowest
2
Diversity:
Lowest
Machipongo (high salinity, intertidal)
Species Richness: Highest
4
Species Evenness: Intermediate
2
3Intermediate
Species Richness:
5 Evenness: Highest
Species
Diversity:
Diversity:
4
polychaetes
bivalves
Highest
1
Famphipods
= 192.75
p < 0.001crabs
F = 59.94
p < 0.001
gastropods
F = 64.38
p < 0.001 fishes
Highest
other
Mean total number of organisms per tray
Total Number of Organisms
2500
A
F = 101.91
p = 0.001
AB
2000
B
C
mixed
shell
1500
1000
500
0
C. ariakensis
C. virginica
York > Patuxent > Severn > Machipongo
(high salinity > mid salinity > low salinity > high salinity, intertidal)
(F = 101.91, p < 0.001)
Mean abundance per gram of oyster biomass
Standardized Total Abundance
Patuxent (mid salinity)
Severn (low salinity)
50
140
120
40
100
30
80
20
60
40
10
20
0
0
C. ariakensis
mixed species
York (high salinity)
250
C. ariakensis
C. virginica
4000
B
200
mixed species
C. virginica
Machipongo (high salinity, intertidal)
3000
150
2000
100
A
A
1000
50
0
0
C. ariakensis
mixed species
C. virginica
C. ariakensis mixed species
C. virginica
Factor
F
p
Tukey Comparisons
Site
23.97
<0.0001
MachipongoA, PatuxentB, YorkB, SevernB
Treatment
6.00
0.0045
C.v.A, C.a.B, mixB
Site*Treatment
5.25
0.0003
Treatment effects driven by PR and YR sites
Species
D. microphthalmus
H. dianthus
N. succinea
P. gouldii
C. equlibra
C. penantis
C. lacustre
E. levis
G. mucronatus
P. tenuis
C. sapidus
M. tenta
M. arenaria
G. strumosus
G. bosci
H. hentz
B. bisuturalis
C. fornicata
R. punctostriatus
U. cinerea
F
29.34
4.33
7.41
4.55
8.78
5.78
8.06
9.62
8.99
7.62
4.09
4.19
6.60
28.82
9.95
3.18
31.23
5.47
11.08
6.57
p
0.0001
0.0181
0.0015
0.0150
0.0005
0.0054
0.0009
0.0003
0.0004
0.0012
0.0223
0.0204
0.0028
0.0001
0.0002
0.0498
0.0001
0.0069
0.0001
0.0028
Tukey Comparisons
C.v.A
C.v.A
C.v.A
C.v.A
C.v.A
C.v.A
C.v.A
C.v.A
C.v.A
C.v.A
C.v.A
C.v.A
C.v.A
C.v.A
C.v.A
C.v.A
C.v.A
C.v.A
C.v.A
C.v.A
C.a.B
C.a.B
C.a.B
mixB
mixB
mixB
mixAB
mixB
mixB
C.a.B
C.a.AB
mixB
mixAB
mixB
mixB
mixAB
mixB
mixAB
mixB
mixB
mixB
mixB
mixB
C.a.B
C.a.B
C.a.B
C.a.B
C.a.B
C.a.B
mixB
mixB
C.a.B
C.a.B
C.a.B
C.a.B
C.a.B
C.a.B
C.a.B
C.a.B
C.a.B
Severn (low salinity)
stress: 0.07
Patuxent (mid salinity)
Global R: 0.349
York (high salinity)
Global R: 0.602
stress: 0.02
stress: 0.03
Significance Level: 0.2%
Machipongo (intertidal)
stress: 0.05
Significance Level: 0.1%
C. ariak ensis
C. virginica
50 C.ariak ensis : 50 C. virginica
Conclusions
• Changes in both faunal assemblages and habitat complexity indices
were more pronounced between sites than within sites.
• C. virginica ‘reefs’ supported higher abundances of over 20 different
species of associated fauna per unit oyster biomass compared to C.
ariakensis ‘reefs’.
• In mid to high salinity subtidal sites, C. virginica’s ability to support
higher abundances of associated fauna per unit of oyster biomass may
be offset by:
• Higher growth rates of C. ariakensis, resulting in higher
oyster biomass per area of oyster bottom.
• Higher average reef height of C. ariakensis reefs.
• ‘Reefs’ containing both oyster species most often supported
abundances similar to those of non-native ‘reefs’, illustrating a
possible effect of multi-species reefs, should C. ariakensis be
introduced.
Acknowledgements
• ESL: Brian Barnes, Alan Birch, Reade Bonniwell, Stephanie Bonniwell, Roshell
Brown, Al Curry, Sean Fate, PG Ross, Edward Smith, Jamie Wheatley
• ESL Summer Aides: Raija Bushnell, Ben Hammer, Sarah Mallette,
Andrew Matkin, Andrew Wilson
• UMD: Steve Allen, Marcy Chen, Jake Goodwin, Mark Sherman, Nancy Ward
• UMCES Horn Point: Stephanie Tobash, Angela Padaletti
• VIMS ABC: Katie Blackshear, Shane Bonnot, Ryan Gill, Karen Hudson
• Statistical and taxonomic assistance: David Gillett