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

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

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

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

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).

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

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.

Mean Densities of Dominant Taxa

Mean Biomass Density of Dominant Taxa

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)

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

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

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

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

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

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

Factor = Predation Naked Goby (Gobiosoma bosc)

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

Microcosm Experiment The Microcosm Array

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

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

Effect of Oyster Biodeposits

Substrate. Predators (p < 0 Substrate*Predators (p < 0.0001) 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.

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. The End!