Lee, S, Ferse, Sebastian C.A. ORCID: https://orcid.org/0000-0003-0930-5356, Ford, Amanda, Wild, C and Mangubhai, S (2017) Effect of sea cucumber density on the health of reef-flat sediments. In: Fiji’s Sea Cucumber Fishery: Advances in Science for Improved Management. , ed. by Mangubhai, S, Lalavanua, W and Purcell, S.W. Wildlife Conservation Society, Suva, Fiji, pp. 54-61. ISBN 978-0-9820263-0-4

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Abstract

Sea cucumbers are thought to play an important role in the recycling and remineralization of
organic matter in reef sands through feeding and bioturbation. However, growing demand and
high prices from Asian markets are driving the overexploitation of sea cucumbers globally,
with little understanding of the consequences of local-scale removal from inshore coral reef
ecosystems. Densities of Holothuria scabra were manipulated in enclosures in situ on a reef
flat adjacent to Natuvu village, on the island of Vanua Levu, Fiji, between August 2015 and
February 2016 to simulate an unfished and an overfished stock density. Two treatments were
used: (i) high sea cucumber stocking density (350 g m-2); and (ii) exclusion of sea cucumbers (0
g m-2). Two controls accounted for cage effects: (i) cage controls (no cage walls); and (ii) natural
density (60 g m-2). Sedimentary oxygen consumption (SOC), grain size distribution, sediment
porosity, and O2 penetration depth were recorded. SOC rates were consistently lower in high-
density enclosures than when sea cucumbers were exclude, indicative of ‘healthy’ sediments.
O2 penetration depth decreased significantly when sea cucumber removal coincided with
elevated sea surface temperatures which are indicative of sediment health decline. Thus the
removal of sea cucumbers reduces the efficiency of reef sediment to function as a filter system
to buffer organic matter pulses, and negatively affects the function and productivity of inshore
reef ecosystems

Document Type:	Book chapter
Programme Area:	UNSPECIFIED
Research affiliation:	Ecology
Date Deposited:	24 Jun 2019 18:11
Last Modified:	26 Mar 2024 13:28
URI:	http://cris.leibniz-zmt.de/id/eprint/2172

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