Localized outbreaks of Acanthaster planci at an isolated and unpopulated reef atoll in the Chagos Archipelago
Outbreaks of the crown-of-thorns starfish (COTS), Acanthaster planci, have occurred at many locations throughout the Indo-Pacific and are a major contributor to widespread coral loss and reef degradation. The causes of outbreaks remain controversial, but are commonly attributed to anthropogenically elevated nutrients and/or over-fishing. If so, it seems unlikely that outbreaks would occur in reef systems that are largely isolated from anthropogenic disturbances. However, high densities of COTS were recently observed on reefs in the Chagos Archipelago, a remote group of atolls and banks within the central Indian Ocean, which experience very limited anthropogenic influence. Aggregations of COTS were first noticed at Eagle Island in 2012, which, although unquantified, appeared to be at outbreak levels, and very high densities (1624 km−2) were subsequently recorded at Danger Island in 2013. While these islands are uninhabited by humans, it is possible that nutrient inputs result from upwelling zones around the Archipelago, or high densities of breeding seabirds. Among islands within the Great Chagos Bank, densities of the red-footed booby Sula sula ranged from 8 to 7888 individuals km−2, with associated guano input ranging from 96 to 25,381 kg island−1 year−1. However, Danger and Eagle Islands where high COTS densities were recorded, had both high and low levels of guano production, respectively, which suggests that outbreaks may not be directly linked to guano nutrient enrichment. Other factors which might be responsible for intermittent COTS outbreaks should be considered in isolated reef systems such as the Chagos Archipelago.
KeywordsCoral Reef Great Barrier Reef Atoll Coral Cover Coral Loss
We thank the captain and crew of the M/V Pacific Marlin for all the work and knowledge that they contributed to this work. We thank the British Indian Ocean Territory (BIOT) administration for assistance and permission to carry out research within the Chagos Archipelago. The authors would like to thank Prof John Pearse and additional anonymous reviewers for their contributions to the manuscript. This research was funded by a UK government Darwin Initiative Grant.
- Bibby CJ, Burgess ND, Hill DA (1992) Bird census techniques. Academic Press, San DiegoGoogle Scholar
- Birkeland C (1989) The Faustian traits of the crown-of-thorns starfish. Am Sci 77:154–163Google Scholar
- Birkeland C, Lucas J (1990) Acanthaster planci: major management problem of coral reefs. CRC Press Boca Raton, FloridaGoogle Scholar
- Carr P (2013) Factors influencing breeding island selection of red-footed booby Sula sula (Linn 1766) in the Chagos Archipelago, central Indian Ocean and the implications for future management plans. University of Warwick, CoventryGoogle Scholar
- Colin PL (1977) The reefs of Cocos-Keeling Atoll, Eastern Indian Ocean. Proc 3rd Int Coral Reef Symp 1:35–42Google Scholar
- Dilmahamod AF (2014) The links between the Seychelles-Chagos Thermocline Ridge and large scale climate modes and primary productivity; and the annual cycle of chlorophyll-a. University of Cape Town, Cape TownGoogle Scholar
- Mendonça VM, Jabri Al MM, Ajmi Al I, Muharrami Al M, Areimi Al M, Aghbari Al HA (2010) Persistent and expanding population outbreaks of the corallivorous starfish Acanthaster planci in the northwestern Indian Ocean: are they really a consequence of unsustainable starfish predator removal through overfishing in coral reefs, or a response to a changing environment. Zool Stud 49:108–123Google Scholar
- Potts DC (1981) Crown-of-thorns starfish: man-induced pest or natural phenomenon? In: Kitching RE, Jones RE (eds) The ecology of pests: some Australian case histories. CSIRO, MelbourneGoogle Scholar
- Pratchett MS, Caballes C, Rivera-Posada JA, Sweatman HPA (2014) Limits to understanding and managing outbreaks of crown-of-thorns starfish (Acanthaster spp.) Oceanogr. Mar Biol 52:133–200Google Scholar
- Sheppard CRC, Ateweberhan M, Bowen BW, Carr P, Chen CA, Clubbe C, Craig MT, Ebinghaus R, Eble J, Fitzsimmons N, Gaither MR, Gan C-H, Gollock M, Guzman N, Graham NAJ, Harris A, Jones R, Keshavmurthy S, Koldewey H, Lundin CG, Mortimer JA, Obura D, Pfeiffer M, Price ARG, Purkis S, Raines P, Readman JW, Riegl B, Rogers A, Schleyer M, Seaward MRD, Sheppard ALS, Tamelander J, Turner JR, Visram S, Vogler C, Vogt S, Wolschke H, Yang JM-C, Yang S-Y, Yesson C (2012) Reefs and Islands of the Chagos Archipelago, Indian Ocean: why it is the world’s largest no-take marine protected area. Aquatic Conserv: Mar Freshw Ecosyst 22:232–261CrossRefGoogle Scholar
- Wilson BR, Stoddart J (1988) A thorny problem—crown-of-thorns starfish in WA. Landscope 3:35–39Google Scholar