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Recent Stratigraphy and Pollen Analysis of Lomawai and Kubulau Mangrove Areas, Fiji.

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Ellison, JC and Strickland, P (2010) Recent Stratigraphy and Pollen Analysis of Lomawai and Kubulau Mangrove Areas, Fiji. Project Report. World Wildlife Fund.

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Abstract

Late Holocene sea level trends of two significant mangrove areas in Fiji were reconstructed by transect-sampled stratigraphic cores, at Lomawai on the western coast of Viti Levu, and Kubulau on the southern coast of Vanua Levu. These cores were investigated using percent organic, radiocarbon dating, and pollen analysis techniques to reconstruct environmental history of the Late Holocene. Results showed at Lomawai that mangroves occurred to at least 3 meters below present, and with a micro-tidal range of mangroves of 1 meter or less this indicates relative sea-level rise at the site in the last 1,000 years at least, consistent with regional subsidence. At Kubulau, stratigraphy was relatively shallow, with little evidence of mangrove presence below current levels suggesting tectonic stability. Inorganic sedimentation at both sites indicated high levels of allochthonous sediment input in association with catchment delivery, with sedimentary rates of around 1.1-2.0 mm a-1 under the present mangroves, though more rapid at the Lomawai seaward edge, perhaps in association with disturbance. The Lomawai mangrove area has been keeping up with relative sea level rise rates higher than global rates in the last several hundred years, with replicated evidence of mangrove stratigraphy far lower than present tidal levels. While mangroves have kept up, there has been a slow landward migration of mangrove zones over the centuries indicating that the rate or relative sea level rise has been slightly higher than the sedimentation rates. Hence both Lomawai and Kubulau mangroves are vulnerable to global increases in the rate of sea level rise, which can be mitigated by continued catchment sediment delivery, and other actions to retain mangrove resilience.

Item Type: Report (Project Report)
Publisher: World Wildlife Fund
Additional Information: The definitive published version is at http://www.wwfpacific.org.fj/
Date Deposited: 10 Mar 2011 05:25
Last Modified: 18 Nov 2014 04:15
URI: http://eprints.utas.edu.au/id/eprint/10541
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