William S. Rodney, Lisa Kellogg & Kennedy T. Paynter

1. Interactions of Top Down and Bottom Up Forces and Habitat Complexity in Experimental Oyster Reef Microcosms William S. Rodney, Lisa Kellogg & Kennedy T. Paynter

2. Talk Structure: • System Description • Experimental Results

3. Talk Structure • System Description • Experimental Results

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.

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

6. Some Key Players:

7. 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!) (* =SFDW, 1 Ricciardi & Bourget 1998, 2 Thayer et al. 1973, 3 Wissing et al. 1973)

12. Macrofaunal Energy Density

13. Talk Structure • System Description • Experimental Results

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)

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

16. Factor = Structural Complexity: 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

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 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

22. Esource*Predators (p = 0.0282)Red Lines = + Predators, Green Lines = - Predators + Biodeposits Control

23. Effect of Oyster Biodeposits

24. Substrate*Predators (p < 0.0001)Red Lines Mean Energy Soucre = Control Green Lines Mean Energy Source = + Biodeposits Predators Absent Predators Present Amphipod Abundance

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. 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!