Impacts of upstream drought on downstream oysters in Apalachicola Bay

1. Impacts of upstream drought on downstream oysters in Apalachicola Bay Laura E. Petes NOAA Climate Program Office

2. Apalachicola Oysters 1909 • 90% of oysters for state of Florida, 10% of oysters for U.S. • Rapid growth rates and high reproductive output • Adapted to brackish conditions (mix of fresh and salt water), natural timing of freshwater input • Reefs provide complex habitat to fish and invertebrates

3. Drought Effects on Bay EB CP DB CP=Cat Point, DB=Dry Bar, EB=East Bay

4. Salinity in Apalachicola Bay EB http://drought.unl.edu/dm/monitor.html CP DB Feb. 20, 2007 Data from ANERR

5. Salinity in Apalachicola Bay EB http://drought.unl.edu/dm/monitor.html CP DB Nov. 20, 2007 Data from ANERR

6. Salinity in Apalachicola Bay EB http://drought.unl.edu/dm/monitor.html CP DB Mar. 28, 2008 Data from ANERR

7. Predictions of increased salinity on oysters • Reduced survival, growth, and condition of oysters; increased prevalence of disease • Range expansion of marine predators (e.g. oyster drills)

8. Dermo Disease • Protozoan parasite (Perkinsus marinus) • Host-to-host transmission; waterborne infective stages abundant in summer • Thrives in high salinity • Can cause sublethal effects and mortality

9. Salinity Impacts on Oysters • Collected at Dry Bar; acclimated at ambient salinity • Randomized into 4 salinity treatments (9, 17, 25, 33 ppt) • 10 large, 10 small oysters per tank • Held at ambient temperature (15°C Winter; 25°C Summer) for 5 weeks • Measured mortality and disease load

10. Mortality

11. Weighted Prevalence Moderate None

12. Conclusions • High salinity (17-25 ppt) leads to oyster mortality • High mortality from Dermo disease in Summer due in part to increased infection severity Implications: • Drought and reduced freshwater input will lead to more summer die-offs of oysters • Consistent with field data (~50% mortality)

13. Predatory Oyster Drills • Stramonita haemastoma (Florida rock snail) • Direct fertilization; lay egg masses • Common predators of oysters in the Panhandle • Increase in number in Apalachicola Bay during periods of high salinity

14. Salinity Impacts on Predators • Predation under different salinity treatments (9, 17, 25, 33 ppt) • One oyster drill and five oysters per container • Oyster mortality and source (predation vs. disease) quantified; dead oysters replaced daily

15. Predator Weight Gain *All oyster drills in 9 ppt died within 48 hours!!!

16. Question: What are the effects of salinity on oyster drill hatching success? Experimental Set-Up: • Egg capsules separated and sorted into groups of 20 • Salinity treatments (9, 17, 25, 33 ppt) • Hatching quantified weekly • Unhatched egg capsules white • Hatched egg capsules clear

17. Oyster Drill Hatching Success

18. Conclusions • Oyster drills and their egg capsules have low tolerance for fresh water Implications: • Both predation and disease important drivers of mortality • Freshwater input would limit predation

19. Implications for Watershed Management Freshwater input is important for oysters due to: • Lowering disease-related mortality • Decreasing the number of oyster predators Future studies should address timing and magnitude of freshwater releases necessary for oysters Water resource and fishery management will become increasingly difficult with climate change

20. Acknowledgments • FSU students: Alicia Brown, Carley Knight, Ryan Corley • Wakulla Co. teachers: Margy Callaghan, Russell Herron • FSUCML staff • ANERR staff • Virginia Institute of Marine Science