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Interactions of Top Down and Bottom Up Forces and Habitat Complexity in Experimental
Oyster Reef Microcosms
William S. Rodney, Lisa Kellogg & Kennedy T. Paynter
Talk Structure:Talk Structure:
I.I. System DescriptionSystem Description
II.II. Experimental Results Experimental Results
Talk StructureTalk Structure
I.I. System DescriptionSystem Description
II.II. Experimental ResultsExperimental Results
Oyster Reef Ecological Functions:
(1) water filtration and regulation of water column phytoplankton dynamics.
(2) enhanced nitrogen cycling between the benthic and pelagic system components.
(3) enhanced recruitment, growth, and survival of oyster populations and a revitalized fishery.
(4) nursery and predation refuge habitat for a diverse community of invertebrates and small fishes.
(5) foraging habitat for transient fish predators.
BB
A typical unrestored oyster reef (A) as compared to a typical restored oyster reef (B).
A
The Study System: Subtidal Mesohaline Oyster Bars in Chesapeake Bay, Maryland.
Some Key Players:
Mean Density of Functional Groups Based on Substrate Use. Blue Bars = Restored, Green Bars = Unrestored, Error bars represent +/- 1 SEM. Asterisks Indicate Statistical Significance..
Infauna
Epifauna*
All Free Living Fauna*
0 500 1000 1500 2000 2500 3000 3500 4000 4500 5000 5500 6000
Fau
nal
Gro
up
Organisms / m2
Mean Densities of Dominant Taxa
Demersal Fish*
Amphipods*
Polychaetes
N. succinea*
Clams
M. balthica
M. arenaria
Xanthid Crabs*
0 200 400 600 800 1000 1200 1400 1600 1800
Fau
nal
Gro
up
Organisms / m2
Mean Biomass Density of Dominant Taxa
0 50 100 150 200 250
Fau
nal
Gro
up
Grams / m2
Clams
Amphipods (x10)*
N. succinea*
Xanthid Crabs*
Demersal Fish*
Grass Shrimp*
Functional Feeding Groups
0 2000 4000 6000 8000 10000
Func
tiona
l Gro
up
Organisms / m2
Carnivore/Omnivores*
Suspension Feeders*
Surface Deposit Feeders
Deep Deposit Feeders (x100)*
Macrofauna Biomass (g) Energy (Fish Food!)
Faunal Group AFDW/WW (%) kcal/g AFDW
Polychaetes:
N. succinea 16.501 6.0702
P. gouldii 14.001 6.0702
Clams 0.087*1 5.7832
Amphipods 16.01 5.2022
P. pugio 16.501 6.3932
Xanthid Crabs 16.50 4.3033
Demersal fish 32.102 5.9002
(* =SFDW, 1 Ricciardi & Bourget 1998, 2 Thayer et al. 1973, 3 Wissing et al. 1973)
Macrofaunal Energy Density
Restored
Unrestored
0
500000
1000000
1500000
2000000
2500000
3000000
3500000
4000000
Treatment
Mea
n E
Den
sity
(J*m
-2)
Talk StructureTalk Structure
I.I. System DescriptionSystem Description
II.II. Experimental ResultsExperimental Results
Research Questions: How can oyster reefs simultaneously function
as both nursery and predation refuge habitat for macrofauna and as fish predator foraging habitat ?
Are deposit feeder densities similar in restored and unrestored habitats because this group isn’t affected by restoration or is there some other reason? (e.g., Bottom Up vs. Top Down Factors and Habitat Complexity)
Experimental Design:Experimental Design:3 x 2 x 2 Factorial ANOVA3 x 2 x 2 Factorial ANOVA
Factor Levels
Substrate Sediment (Low Complexity)
Half Shell (Moderate Complexity)
Clump (High Complexity)
Energy Source + Biodeposits
(Bottom Up) Control (natural seston)
Predation Predators Present
(Top Down) Predators Absent
Factor = Structural Complexity:Factor = Structural Complexity:
Sediment Half Shell Clump (Reef)
Factor = Energy SourceFactor = Energy Source
The Feces Factory (Oyster Biodeposits Collector)
Factor = PredationFactor = Predation
Naked Goby (Gobiosoma bosc)
The Response Variable: Melita nitidaThe Response Variable: Melita nitida
Microcosm Experiment
The Microcosm Array
3x2x2 Factorial ANOVADependent Variable: log amphipod abundance Sum of Source DF Squares Mean Square F Value Pr > F
Model 11 13.971 1.270 16.43 <.0001 Error 36 2.783 0.077 Corrected Total 47 16.755 R-Square Coeff Var Root MSE logamphs Mean 0.833866 19.51354 0.2786 1.424991 Source DF Type I SS Mean Square F Value Pr > F Substrate 2 3.60534590 1.80267295 24.39 <.0001 Esource 1 1.68953482 1.68953482 22.86 <.0001 Predators 1 5.26410821 5.26410821 71.22 <.0001 Substrate*Esource 2 0.45876893 0.22938446 3.10 0.0574 Esource*Predators 1 0.38745329 0.38745329 5.24 0.0282 Substrate*Predators 2 2.28477170 1.14238585 15.46 <.0001 Substr*Esourc*Predat 2 0.36087834 0.18043917 2.44 0.1017
Esource*Predators (p = 0.0282)Red Lines = + Predators, Green Lines = - Predators
0
20
40
60
80
100
120
140
160
180
Mud Half Shell Reef
Am
phip
od A
bund
ance
0
20
40
60
80
100
120
140
160
180
Mud Half Shell Reef
Control + Biodeposits
Effect of Oyster BiodepositsEffect of Oyster Biodeposits
+ Biodeposits
Control
0.00
20.00
40.00
60.00
80.00
100.00
120.00
140.00
160.00
Microcosm Treatment
Mea
n A
mph
ipod
Abu
ndan
ce
(am
phip
ods/
mic
roco
sm)
0
20
40
60
80
100
120
140
160
180
Mud Half Shell Reef
0
20
40
60
80
100
120
140
160
180
Mud Half Shell Reef
Predators Absent Predators Present
Am
ph
ipo
d
Ab
un
dan
ceSubstrate*Predators (p < 0.0001)Red Lines Mean Energy Soucre = Control
Green Lines Mean Energy Source = + Biodeposits
Conclusions: Addition of a moderate amount of oyster biodeposits
(OBD) had a profound effect on amphipod production. Amphipod abundance was 3.5 times greater in treatments that received OBD. The effect of OBD was modified by the presence of predators.
The effect of predators was mitigated by reef structural complexity. The combined effects of OBD and reef structure allowed for high amphipod production in the presence of predators.
The End!
Acknowledgments
I wish to thank: Mark Sherman, Sara Rowland and Paul Miller of the Paynter Lab.
Bud Millsaps, and various other CBL folks.