Reef-associated fauna in Chesapeake Bay: Does oyster species affect habitat function?

H. Harwell*H. Harwell*11, P. Kingsley-Smith, P. Kingsley-Smith22, M. Kellogg, M. Kellogg33, , K. Paynter, Jr.K. Paynter, Jr.33 and M. Luckenbach and M. Luckenbach11..

11Virginia Institute of Marine Science, The College of William & Mary Virginia Institute of Marine Science, The College of William & Mary 22South Carolina Department of Natural Resources,South Carolina Department of Natural Resources,33University of Maryland University of Maryland

Illustration by Kent Forrest, © VIMS

Complexity

Abu

ndan

ce

• Macroinvertebrate densities and species richness are generally positively correlated with structural complexity (Crowder and Cooper 1982, Diehl 1992).

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.

C. virginica C. ariakensis

Photo credits: Mark Luckenbach

C. ariakensis

C. sikamea

Does habitat complexity vary between oyster species?

If so, how will these differences affect habitat utilization?

Compare the complexity of experimental Compare the complexity of experimental C. ariakensisC. ariakensis and and C. virginicaC. virginica reefs by examining vertical relief and surface reefs by examining vertical relief and surface complexity.complexity.

Evaluate and compare the utilization of experimental Evaluate and compare the utilization of experimental C. C. ariakensisariakensis and and C. virginicaC. virginica reefs by other organisms. reefs by other organisms.

Investigate the relationship between the development of Investigate the relationship between the development of reef associated communities and habitat complexity.reef associated communities and habitat complexity.

ObjectivesObjectives

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

Atlantic OceanAtlantic Ocean

Che

sape

ake

Bay

Che

sape

ake

Bay

Delaware Delaware BayBay

SEVERN RIVERSEVERN RIVERSubtidal (3 - 4m)Low salinity (3 - 14 mean daily psu)Low predation pressureLow Dermo / No MSX

PATUXENT RIVERPATUXENT RIVERSubtidal (3 - 4m)Low salinity (8 - 16 mean daily psu)Moderate predation pressureLow Dermo / No MSX

YORK RIVERYORK RIVERSubtidal (1 - 2m)Mid salinity (9 - 21 mean daily psu)High predation pressureHigh Dermo / High MSX

MACHIPONGO RIVERMACHIPONGO RIVERIntertidalHigh salinity (5 -33 mean daily psu)High predation pressureHigh 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 Shannon-Wiener diversity.

• Indices of habitat complexity (maximum and average vertical heights, surface rugosity) between sites and treatments.

• Nonparametric multi-dimensional scaling (MDS) and Analysis of Similarity (ANOSIM) to evaluate variations in community structure between 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.

80

40

20

60

80

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80

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60

80

40

20

60

C. virginicaC. ariakensis

C. virginicaC. ariakensis

C. virginicaC. ariakensis

C. virginicaC. ariakensis

Total number of live oysters across all cages

Total number of live oysters across all cages

Total number of live oysters across all cages

Total number of live oysters across all cages

0 60 90 12030

Machipongo River, VA July 5 th 2006

York River, VA July 24 th 2006

Patuxent River, MD July 10 th 2006

Severn River, MD July 17 th 2006

Shell length (mm)

80

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20

60

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60

C. virginicaC. ariakensis

C. virginicaC. ariakensis

C. virginicaC. ariakensis

C. virginicaC. ariakensis

Total number of live oysters across all cages

Total number of live oysters across all cages

Total number of live oysters across all cages

Total number of live oysters across all cages

0 60 90 120300 60 90 12030

Machipongo River, VA July 5 th 2006

York River, VA July 24 th 2006

Patuxent River, MD July 10 th 2006

Severn River, MD July 17 th 2006

Shell length (mm)

0

2

4

6

8

C. ariakensis C. v irginica mixed shell

0

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C. ariakensis C. v irginica mixed shell

0

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8

C. ariakensis C. v irginica mixed shell

0

2

4

6

8

C. ariakensis C. v irginica mixed shell

maximum 'reef' height mean 'reef' height

Height from top of tray (cm)

Severn Patuxent

York Machipongo

Factor F p Tukey Comparisons

Site 25.95

46.32

< 0.0001

<0.0001

YorkA, PatuxentA, SevernA, MachipongoB

PatuxentA, YorkA, SevernB, MachipongoC

Treatment 36.11

68.29

< 0.0001

< 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

< 0.0001

Treatment effects driven by YR and PR sites

Treatment effects driven by YR and PR sites

Habitat Complexity: Surface Rugosity

1

1.2

1.4

1.6

C. ariakensis C. v irginica mixed shell

1

1.2

1.4

1.6

C. ariakensis C. v irginica mixed shell

1

1.2

1.4

1.6

C. ariakensis C. v irginica mixed shell

1

1.2

1.4

1.6

C. ariakensis C. v irginica mixed shell

Surface rugosity Index

Severn (low salinity) Patuxent (mid salinity)

York (high salinity) Machipongo (high salinity, intertidal)

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

Severn(low)

Patuxent(mid)

York(high)

Machipongo(high, intertidal)

# of species 22 35 63 48

# of dominant taxa 8 6 12 16

Total # of associated organisms

17,009 32,419 40,695 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

Between-sites Comparison of Reef-associated Fauna

July 2006

Severn (low salinity)

Machipongo (high salinity, intertidal)

Patuxent (mid salinity)

York (high salinity)

amphipodspolychaetes crabs

fishesgastropodsbivalves

other

Dominant Reef-associated Fauna

1 1

3

1

2

21

4

45

32

1

Species Richness: Lowest

Species Evenness: IntermediateDiversity: Lowest

Species Richness: Highest

Species Richness: Intermediate

Species Richness: Intermediate

Species Evenness: Intermediate

Species Evenness: Lowest

Species Evenness: Highest

Diversity: Highest Diversity: Highest

Diversity: Lowest

F = 192.75 p < 0.001F = 59.94 p < 0.001F = 64.38 p < 0.001

0

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C. ariakensis C. virginica mixed shell

Mea

n t

otal

nu

mb

er o

f or

gan

ism

s p

er

tray

Severn Patuxent York Machipongo

A AB

B C

> > >

(F = 101.91, p < 0.001)

F = 101.91 p = 0.001

(high salinity > mid salinity > low salinity > high salinity, intertidal)

Total Number of Organisms

0

1000

2000

3000

4000

C. ariakensis mixed species C. virginica

0

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C. ariakensis mixed species C. virginica0

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C. ariakensis mixed species C. virginica

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C. ariakensis mixed species C. virginica

Severn (low salinity) Patuxent (mid salinity)

York (high salinity) Machipongo (high salinity, intertidal)

A A

B

Mea

n ab

unda

nce

per

gram

of

oyst

er b

iom

ass

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

Standardized Total Abundance

Species F p Tukey Comparisons

C. equlibra 8.78 0.0005 C.v.A mixB C.a.B

C. penantis 5.78 0.0054 C.v.A mixB C.a.B

C. lacustre 8.06 0.0009 C.v.A mixAB C.a.B

E. levis 9.62 0.0003 C.v.A mixB C.a.B

G. mucronatus 8.99 0.0004 C.v.A mixB C.a.B P. tenuis 7.62 0.0012 C.v.A C.a.B mixB

D. microphthalmus 29.34 0.0001 C.v.A C.a.B mixB

H. dianthus 4.33 0.0181 C.v.A C.a.B mixB

N. succinea 7.41 0.0015 C.v.A C.a.B mixB P. gouldii 4.55 0.0150 C.v.A mixB C.a.B

C. sapidus 4.09 0.0223 C.v.A C.a.AB mixB

M. tenta 4.19 0.0204 C.v.A mixB C.a.B

M. arenaria 6.60 0.0028 C.v.A mixAB C.a.B

G. strumosus 28.82 0.0001 C.v.A mixB C.a.B

G. bosci 9.95 0.0002 C.v.A mixB C.a.B

H. hentz 3.18 0.0498 C.v.A mixAB C.a.B

B. bisuturalis 31.23 0.0001 C.v.A mixB C.a.B

C. fornicata 5.47 0.0069 C.v.A mixAB C.a.B

R. punctostriatus 11.08 0.0001 C.v.A mixB C.a.B

U. cinerea 6.57 0.0028 C.v.A mixB C.a.B

stress: 0.03

Global R: 0.349 Significance Level: 0.2%

Patuxent (mid salinity)

stress: 0.02

Global R: 0.602 Significance Level: 0.1%

York (high salinity) stress: 0.05Machipongo (intertidal)

C. ariak ensis C. virginica 50 C.ariak ensis : 50 C. virginica

stress: 0.07 Severn (low salinity)

Conclusions

• Changes in both faunal assemblages and habitat complexity indices were more pronounced between sites than within sites.

• 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:

• C. virginica ‘reefs’ supported higher abundances of over 20 different species of associated fauna per unit oyster biomass compared to 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.

• Higher growth rates of C. ariakensis, resulting in higher oyster biomass per area of oyster bottom.

• Higher average reef height of C. ariakensis reefs.

• 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

Acknowledgements