How to Cite

EVIDENCE OF RESILIENCE IN REEF ISLANDS IN RESPONSE TO RISING SEA LEVEL ON HUVADHOO ATOLL, MALDIVES. (2020). Coastal Engineering Proceedings, 36v, papers.43. https://doi.org/10.9753/icce.v36v.papers.43


Reef islands are at the forefront of concern for future accelerating sea-level rise since their low-lying and isolated nature puts them at higher risk of marine inundation compared to continental coastlines. However, the perceived threat of complete submersion as implied by projected future sea-level rise and current island elevations do not consider the morphologically resilient nature of reef island systems. In particular, the role of sediment supply in the resilience of these islands is still relatively poorly studied. This study presents detailed descriptions of the sedimentary characteristics and stratigraphy of two lagoonal platform islands in Huvadhoo Atoll, Maldives, that formed during periods of Holocene sea-level rise. Island subsurface stratigraphy was reconstructed by analysing the skeletal composition and textural properties of 306 sediment samples from 37 cores extracted across the islands. Island sediments were dominated by coral sands with varied proportions of secondary constituents (molluscs, Halimeda, foraminifera, and crustose coralline algae). Downcore variations in composition show that the proportion of coral sands decrease with depth and the proportion of molluscs and Halimeda increase with depth (with the exception of cores that terminated on lagoon infill). The increased proportion of Halimeda and molluscs in these early island deposits may have resulted from the catch-up growth strategy of the reef during the mid-Holocene highstand as both organisms have high turnover rates and directly contribute to sediment production after death. The sedimentological response of increased Halimeda and molluscs highlights the resilient and dynamic nature of reef islands and the ability of reefs to adjust ecologically to changing sea levels.

Recorded Presentation from the vICCE (YouTube Link): https://youtu.be/gy3zhqocMGw


Ampou, E. E., Johan, O., Menkès, C. E., Niño, F., Birol, F., Ouillon, S., & Andréfouët, S. 2017. Coral mortality induced by the 2015–2016 El-Niño in Indonesia: the effect of rapid sea level fall. Biogeosciences, European Geosciences Union, 14(4), 817-826.

Blott, S. J., & Pye, K. 2001. GRADISTAT: a grain size distribution and statistics package for the analysis of unconsolidated sediments. Earth surface processes and Landforms, 26(11), 1237-1248.

East, H. K., Perry, C. T., Kench, P. S., Liang, Y., & Gulliver, P. 2018. Coral reef island initiation and development under higher than present sea levels. Geophysical Research Letters, 45(20), 11-265.

Dawson, J. L., & Smithers, S. G. 2010. Shoreline and beach volume change between 1967 and 2007 at Raine Island, Great Barrier Reef, Australia. Global and Planetary Change, 72(3), 141-154.

Ford, M.R. 2009. Sedimentological implications of durability and physical taphonomic processes on a fringing reef, Lizard Island, Australia (Unpublished doctoral dissertation), University of Auckland, Auckland, New Zealand.

Ford, M. R., & Kench, P. S. 2014. Formation and adjustment of typhoon-impacted reef islands interpreted from remote imagery: Nadikdik Atoll, Marshall Islands. Geomorphology, 214, 216-222.

Hammer, Ø., Harper, D. A. T., & Ryan, P. D. 2001. PAST: Paleontological Statistics Software Package for Education and Data Analysis Palaeontol. Electronica, 4, 1-9.

Hewins, M. R., & Perry, C. T. 2006. Bathymetric and environmentally influenced patterns of carbonate sediment accumulation in three contrasting reef settings, Danjugan Island, Philippines. Journal of Coastal Research, 22(4), 812-824.

Hillis-Colinvaux, L. 1980. Ecology and taxonomy of Halimeda: primary producer of coral reefs. Advances in Marine Biology, 17, 1-327.

Kench, P. S., McLean, R. F., Owen, S. D., Ryan, E., Morgan, K. M., Ke, L., ... & Roy, K. 2020. Climate-forced sea-level lowstands in the Indian Ocean during the last two millennia. Nature Geoscience, 13(1), 61-64.

Kench, P. S., Smithers, S. G., McLean, R. F., & Nichol, S. L. 2009. Holocene reef growth in the Maldives: evidence of a mid-Holocene sea-level highstand in the central Indian Ocean. Geology, 37(5), 455-458.

Kench, P. S., Thompson, D., Ford, M. R., Ogawa, H., & McLean, R. F. 2015. Coral islands defy sea-level rise over the past century: Records from a central Pacific atoll. Geology, 43(6), 515-518.

Liang, Y., Kench, P. S., Ford, M. R., & East, H. K. 2016. Lagoonal reef sediment supply and island connectivity, Huvadhu Atoll, Maldives. Journal of Coastal Research, 75, 587-591.

Morgan, K. M., & Kench, P. S. 2016. Reef to island sediment connections on a Maldivian carbonate platform: using benthic ecology and biosedimentary depositional facies to examine island‐building potential. Earth Surface Processes and Landforms, 41(13), 1815-1825.

Neumann, A. C. & MacIntyre, I. 1985. Reef response to sea level rise: keep-up, catch-up or give-up, Proceedings of the Fifth International Coral Reef Congress, ICRS, 105-110.

Perry, C.T., Kench, P.S., Smithers, S.G., Riegl, B., Yamano, H., & O’Leary, M.J. 2011. Implications of reef ecosystem change for the stability and maintenance of coral reef islands. Global Change Biology, 17(2), 3679-3696.

Webb, A. P., & Kench, P. S. 2010. The dynamic response of reef islands to sea-level rise: Evidence from multi-decadal analysis of island change in the Central Pacific. Global and Planetary Change, 72(3), 234-246.

Yamano, H., Miyajima, T., & Koike, I. 2000. Importance of foraminifera for the formation and maintenance of a coral sand cay: Green Island, Australia. Coral Reefs, 19(1), 51-58.

Authors retain copyright and grant the Proceedings right of first publication with the work simultaneously licensed under a Creative Commons Attribution License that allows others to share the work with an acknowledgement of the work's authorship and initial publication in this Proceedings.