1. William S. Rodney, Lisa Kellogg & Kennedy T. Paynter
Interactions of Top Down and Bottom Up Forces and Habitat Complexity in Experimental Oyster Reef Microcosms
My name is Bill Rodney, I’m a grad student of Ken Paynter’s in the MEES…. I sampling macrofauna on oyster reefs last year…
William S. Rodney, Lisa Kellogg & Kennedy T. Paynter

2. Talk Structure: System Description Experimental Results
My talk will be in 2 sections

3. Talk Structure System Description Experimental Results
My talk will be in 2 sections

4. 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.
These are what we believe to be the major ecological funtions of oyster reefs.
My talk concerns the last 2

5. The Study System: Subtidal Mesohaline Oyster Bars in Chesapeake Bay, Maryland.
A typical unrestored oyster reef (A) as compared to a typical restored oyster reef (B).

6. Some Key Players:
We collected more than 19,000 free living macrofaunal organisms during the course of the study. Of these, 70% were collected from restored plots. If we include sessile or “fouling” organisms (barnacles, mussels, anemones and tunicates) in our total, then more than 40,000 organisms were collected with 86% being from restored plots

7. Mean Density of Functional Groups Based on Substrate Use
Mean Density of Functional Groups Based on Substrate Use. Blue Bars = Restored, Green Bars = Unrestored, Error bars represent +/- 1 SEM. Asterisks Indicate Statistical Significance.

8. Mean Densities of Dominant Taxa

9. Mean Biomass Density of Dominant Taxa

11. Macrofauna Biomass (g)  Energy (Fish Food!)
Faunal Group
AFDW/WW (%)
kcal/g AFDW
Polychaetes:
N. succinea
16.501
6.0702
P. gouldii
14.001
Clams
0.087*1
5.7832
Amphipods
16.01
5.2022
P. pugio
6.3932
Xanthid Crabs
16.50
4.3033
Demersal fish
32.102
5.9002
Because the results suggest high potential for Trophic Energy Transfer n Restored: We decided to convert biomass data to energy currency.
Those aren’t exponents but footnotes
(* =SFDW, 1 Ricciardi & Bourget 1998, 2 Thayer et al. 1973, 3 Wissing et al. 1973)

12. Macrofaunal Energy Density
This does not include the “outlier” Howell Point site, that is another story in itself.

13. Talk Structure System Description Experimental Results
My talk will be in 2 sections

14. 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)
Other Reason: Interaction of top down and Bottom Up Factors

15. Experimental Design: 3 x 2 x 2 Factorial ANOVA
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

16. Factor = Structural Complexity:
Representing Complexity Gradient Low – Medium - High
Sediment
Half Shell
Clump (Reef)

17. Factor = Energy Source
The Feces Factory (Oyster Biodeposits Collector)

18. Factor = Predation
Naked Goby (Gobiosoma bosc)

19. The Response Variable: Melita nitida
Our “Model Deposit Feeder” is a Brooding Species

20. Microcosm Experiment
The Microcosm Array

21. 3x2x2 Factorial ANOVA Dependent Variable: log amphipod abundance
Sum of
Source DF Squares Mean Square F Value Pr > F
Model <.0001
Error
Corrected Total
R-Square Coeff Var Root MSE logamphs Mean
Source DF Type I SS Mean Square F Value Pr > F
Substrate <.0001
Esource <.0001
Predators <.0001
Substrate*Esource
Esource*Predators
Substrate*Predators <.0001
Substr*Esourc*Predat

22. Esource*Predators (p = 0.0282) Red Lines = + Predators, Green Lines = - Predators
Control
+ Biodeposits
In Seston only treat,s, the diff between means for Pred.s x No Pred.s stays constant across all levels of substrate.
In +OBD treat.s, the diff between means for Pred.s x No Pred.s are different across levels of substrate

23. Effect of Oyster Biodeposits

24. Substrate. Predators (p < 0
Substrate*Predators (p < ) Red Lines Mean Energy Soucre = Control Green Lines Mean Energy Source = + Biodeposits
Predators Absent
Predators Present
Amphipod Abundance
In the absence of pred.s, the diff.s between means for OBD x Seston are sig. diff across all levels of Substrate.
In the presence of pred.s, the means for OBD x Seston are not diff in mud, but become increasingly more diff. as Substrate complexity increases.

25. 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.

26. 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.
The End!