Spatial variation in the benthic reef community of Kiritimati Island after a coral mass mortality event Rebecca Hansen, Department of Biology, University of Victoria Supervised by Dr. Julia Baum

Introduction Results – Community • 504 photos analyzed • Benthic communities are the foundation of tropical reefs • Coral recovery measured by juvenile Acropora and Pocillopora colonies and by Figure 4. Juvenile Acropora (left) and coral cover Pocillopora (right) colonies. • Calculated percent cover by Figure 1. Benthic reef organisms including coral, encrusting algae, and macroalgae. site for coral, crustose 1 coralline algae, Peysonnelia • Benthic organisms are sensitive to stressors e.g. warming algae, fleshy macroalgae, • Climate change is increasing the frequency and severity of turf algae, cyanobacteria, coral mass mortality events worldwide2 other biotic and abiotic • Modelling with GLMMs and PERMANOVA Figure 5. Substrate identification process. Results – Coral

Acropora

Figure 2. Coral reef before (left) and after (right) the 2015-2016 mass coral bleaching and mortality event on Kiritimati Island. Photo credits: Baum Lab. • Coral loss can lead to larger changes in the composition of the benthic community • Previous studies have documented return of coral cover, Figure 7. Principle Coordinates Analysis of benthic community composition by site. Distances shift to turf or macroalgae, dominance by rubble3,4 represent Bray-Curtis dissimilarities. • High variation in outcomes even on a local scale, many possible sources of variation5,6 Future directions - -

Objective Pocillopora • Investigate relationships between juvenile colony counts Acropora Pocillopora and cover by substrates that promote or deter recruitment To determine the effect of depth and wind exposure on the Figure 6. Boxplots of total Acropora (left) and Pocillopora (right) colony counts per site, comparing • Investigate the effect of depth and wind exposure on the composition of the reef community as it recovers from a sites from two depth strata and two levels of wind exposure. mass coral bleaching and mortality event composition of the coral community • Incorporate other variables e.g. primary productivity into Methods analyses • Kiritimati Island, central References equatorial Pacific 1.Huston, M. A. Patterns of Species Diversity on Coral Reefs. Annual Review of Ecological Systems 16, 149–177 (1985). 2.Hughes, T. P. et al. Spatial and temporal patterns of mass bleaching of corals in the Anthropocene. • Data from surveys in 2019, Science 359, 80–83 (2018). three years after El Niño 3.Baker, A. C., Glynn, P. W. & Riegl, B. Climate change and coral reef bleaching: An ecological assessment of long-term impacts, recovery trends and future outlook. Estuarine, Coastal and Shelf Science 80, 435–471 (2008). 4.Chong-Seng, K. M., Graham, N. A. J. & Pratchett, M. S. Bottlenecks to coral recovery in the Seychelles. Coral • Low human disturbance Reefs 33, 449–461 (2014). 5.Stobart, B., Teleki, K., Buckley, R., Downing, N. & Callow, M. Coral recovery at Aldabra Atoll, Seychelles: five • 8 windward and 8 leeward years after the 1998 bleaching event. Phil. Trans. R. Soc. A. 363, 251–255 (2005). 6.Golbuu, Y. et al. Palau’s coral reefs show differential habitat recovery following the 1998-bleaching event. Coral locations Reefs 26, 319–332 (2007). • 2 sites at each location: Acknowledgements shallow and deep Dr. Andrew Halford (Coastal Fisheries Programme), Dr. Julia • 16 benthic images per site Figure 7. Boxplots of mean coral cover per site (%), comparing sites from two depth strata and two Figure 3. Map of study locations. levels of wind exposure. Baum, Dominique Maucieri & the Baum Lab.