1. A stormy future for coastal carbon : Assessing impacts of climatic perturbation on carbon transport, processing, and storage in coastal regions Joey Crosswell University of Technology Sydney Michael S. Wetz Texas A&M University at Corpus Christi Burke Hales Oregon State University Hans W. Paerl University of North Carolina at Chapel Hill

2. Atmospheric CO 2 Coastal carbon-climate feedback Coastal Carbon + or - ? + +

3. Normal Storm Flood

4. Transport of terrestrial C to coastal waters Horowitz et al. 2014

5. Does a shift toward more intense events affect the quantity and quality of C input to coastal waters? = ?

6. Dhillon and Inamdar 2013 Jung et al. 2014 Najjar et al. 2010 Intense events mobilize more POC and more labile DOC

7. Honduran Mangroves Hurricane Mitch (1998): Cat. 4 Breton Sound Marsh, LA Hurricanes Katrina & Rita (2005): Cat. 4 Loss of 520 km 2 of coastal marsh Mobilized 15.4 Tg of sediment OC Global salt marsh C burial: 4 - 87 Tg-C yr -1 Mobilization of wetland C in coastal waters Cahoon and Hensel 2002

8. What is the ultimate fate of mobilized C? Stored in coastal sediments Released to the atmosphere as CO 2 Exported to the ocean

9. Chen et al. 2009 Apalachicola Bay, FL Hurricane Frances (2002) During storm: Rapid increase in sediment-water CO 2 flux Mobile Bay, AL Hurricane Ivan (2004) Park et al. 2007

10. Before Irene (2011)During Irene (2011) Chesapeake Bay Hurricane Isabel (2003) Days During storm: Rapid increase in water-air CO 2 flux Crosswell in prep.

11. Aug. 2004 Oct. 2005 Apr. 2006 Lohrenz et al. 2010 Storm Post-storm Katrina & Rita (2005)

12. Aug. 2004 Oct. 2005 Apr. 2006 Lohrenz et al. 2010 Apr. 2011 June 2011 Aug. 2011 Storm Flood only Post-storm Flood Post-Flood Mississippi-Atchafalaya flood (2011) Bianchi et al. 2013 Katrina & Rita (2005) Flood changed estuary-shelf system from CO 2 sink to source 83% of CO 2 efflux sustained by respiration of terrestrial DOC

13. Post storm: Fate of mobilized POC depends on basin/coast type Export to deep ocean Progressive & cumulative decay

14. Crosswell et al. 2014 >35 m s -1 sustained winds over APS >200 mm rainfall Storm surge of 3-4 m in APS Hurricane Irene (2011) Albemarle-Pamlico Sound system, NC Annual atm CO 2 sink year prior to Irene

15. Irene induced CO 2 efflux Changed APS from annual CO 2 sink to large CO 2 source 4X annual Riverine DIC + TOC input 80% of post-storm CO 2 efflux in freshwater region was supported be OC respiration

17. A substantial amount of C mobilized by extreme events is released to the atmosphere in coastal waters rather than simply relocated from a terrestrial to an oceanic C sink. The magnitude of these episodic CO 2 emissions can offset C that accumulates over much longer timescales If the intensity of storms and floods increases, long-term C storage in coastal regions will ultimately be reduced Conclusions

18. Next steps Large uncertainty in during-storm fluxes In-situ observations during storms/Better accounting of C stocks immediately before and after storms Many systems lack baseline C data needed to assess long-term impacts of extreme events Identify systems which are most susceptible to climatic disturbance and implement carbon monitoring programs years before extreme events, i.e. now