Ecological considerations for oyster restoration: interactions between oyster larvae and reef-associated fauna

1. Ecological considerations for oyster restoration: interactions between oyster larvae and reef-associated fauna Brian B. Barnes*, Mark W. Luckenbach, Peter R. Kingsley-Smith

2. 120 90 Commercial oyster landings (millions of pounds) 60 Virginia landings Maryland landings 30 2000 1920 1940 1960 1980 1900 1880 Plight of oysters in Chesapeake Bay Current Crassostrea virginica population levels in Chesapeake Bay are < 1% biomass of those at the start of the last century (Newell, 1988) chesapeakebay.noaa.gov

3. Supplementing shell substrate • Shells are limiting to epibenthic fauna AND restoration managers • Substrate additions are often done without regard for how substrate colonization affects oysters • Epifaunal interactions research is often conducted using artificial substrates Shell planting on Rappahannock River

4. Research Objectives • Investigate the effects of single-species epifaunal populations on the recruitment of oyster larvae using natural substrates • Effect of water soluble cues • Effect of clamworms (Neanthes succinea)

5. Rappahannock River site a Pungoteague Creek site VIMS ESL b Collection sites b a Images from maps.google.com

6. Experimental treatments Membranipora tenuis No fouling Cliona sp. Balanus improvisus Barnacle Mould Dead Barnacle

7. . . . . . . . . . . . . . . . . . . . . . . Microcosm design – Effect of epifauna ~ 75 larvae 50 ml adult oyster bathwater Test shell (~3 cm x ~3 cm) Combusted very fine sand (63 – 125 μm) 4.3 cm 5.7 cm

8. . . . . . . . . . . . . . . . . . . . . . . Overall layout = x 16

9. Results – Effect of epifauna on oysters: Settlement rate, Experiment 1 (C. a.) *

10. Results – Effect of epifauna on oysters: Settlement Rate

11. Results – Effect of epifauna on oysters: Mortality

12. . . . . . . . . . . . . . . . . . . . . . . Microcosm design – Effect of bathwaters ~ 75 larvae 50 ml adult bathwater 4.3 cm 5.7 cm

13. * * * * * * Results – Bathwater experiments * * *

14. Conclusions • No clear differences between C. virginica and C. ariakensis larvae • Balanus improvisus presence likely affects settling oyster larvae • Increased structure likely not important • Water soluble cue causes mortality, increased settlement • Membranipora tenuis largely inert to mortality and settlement rate of oyster larvae • Cliona sp. causes mortality to oyster larvae and deters settlement

15. Conclusions (continued) • Clamworms (Neanthes succinea) are voracious predators on oyster larvae; their bathwater also causes mortality • Average predation rate = ~11 larvae day-1 worm-1 • Field population abundance = ~10,000 clamworms m-2 • Oyster bathwater causes mortality to conspecifics • Effect significant after 2 days • Reef-associated invertebrates certainly influence settling oyster larvae • Effect is not uniform or easily predictable • Interactions should inform the location and timing of shell planting projects

16. Acknowledgements • VIMS – Eastern Shore Lab • Steph Bonniwell, Lynn Walker, Heather Harwell, Edward Smith, Roshell Brown, Alan Birch, Sean Fate, Reade Bonniwell, Al Curry, Jamie Wheatley, Linda Ward, Summer Aides • VIMS – Gloucester Point • Roger Mann, John Brubaker, Missy Southworth, Juli Harding, Peter van Veld • UMD – CBL • Mario Tamburri • Funding • Kelley Watson Fellowship, Eastern Shore Lab Research Grants, GSA Mini-Grant, VIMS Assistantship