The evolution of Maldivian coral reef rim islands
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Date
2017-04-07Author
East, Holly Kate
Date issued
2017-04-07
Type
Thesis or dissertation
Language
en
Publisher
University of Exeter
Embargo
2019-06-19
Reason for embargo
Embargo period of 18 months to allow time to prepare papers for publication.
Abstract
The first detailed investigation of Maldivian rim island development and reef-to-island connectivity is presented. Study sites were selected on windward and leeward rim aspects of Huvadhu Atoll, and analyses were undertaken at a millennial, contemporary and near-future temporal scales. At millennial temporal scales, contrasting models of island development were presented for the windward and leeward sites. Marked between-site differences were found in the timings of island initiation (2,800-2,000 cal. yr. B.P. and 4,200-3,600 cal. yr. B.P. at the windward and leeward sites respectively). Hence, sea-level does not represent the sole control upon island formation. The period of island initiation and heightened mobility occurred during the mid-Holocene sea-level highstand. Future sea-level rise may thus reactivate the process regime responsible for reef island initiation, potentially inducing further island building and/or heightened island mobilisation. Contemporary analyses highlighted the homogeneity of the sediment reservoir across marine, beach and island sediments. Specifically, sand-grade coral was dominant across all samples within both sites (>50%). The most likely source of sand-grade coral is excavator parrotfish, which was consistent with ecological survey-based estimates of sediment production (excavator parrotfish accounted for 72.8% and 68.2% of sediment production at the windward and leeward sites). The highest sediment production rates were found within the lagoonward environments (59.4% and 75.4% at the windward and leeward sites), which is consistent with the more recent lateral lagoonward mode of island building. With regard to near-future analyses, the apparent recent areal expansion of seagrass beds demonstrated the capacity of ecological changes to cause shifts in sediment production budgets (contributing an additional ~243 tonnes yr-1 of sediment on the leeward rim platform). In addition, significant increases in benthic sediment mobility were found at both study sites under sea-level rise scenarios. Increases in mobility were markedly larger in magnitude at the leeward site than at the windward site. A challenge for the adaptive capacity of atoll nations is thus to acknowledge this atoll-scale diversity in future management strategies.
Funders/Sponsor
NERC
Citation
East, H. K., Perry, C. T., Kench, P. S., & Liang, Y. (2016). Atoll-scale comparisons of the sedimentary structure of coral reef rim islands, Huvadhu Atoll, Maldives. Journal of Coastal Research, 75(sp1), 577-581.
Advisor
Perry, Chris
Kench, Paul
Degree title
PhD in Physical Geography
Qualification level
Doctoral
Qualification name
PhD