Status of coral reefs of Upolu (Independent State of Samoa) in the South West Pacific and recommendations to promote resilience and recovery of coastal ecosystems

https://doi.org/10.1016/j.marpolbul.2018.02.044Get rights and content

Highlights

  • We assessed the health of reef ecosystems at Samoa in the remote South West Pacific.

  • Despite the distance to large urban centers, live coral cover was extremely low.

  • Reef fish were 10% smaller than at neighboring islands.

  • Coral cover was higher within two local marine protected areas.

  • Remote reef ecosystems are not immune to local and global anthropogenic impacts.

Abstract

Coral reef ecosystems worldwide are immediately threatened by the impacts of climate change. Here we report on the condition of coral reefs over 83 km of coastline at the island of Upolu, Samoa in the remote South West Pacific in 2016 during the Tara Pacific Expedition. Despite the distance to large urban centers, coral cover was extremely low (<1%) at approximately half of the sites and below 10% at 78% of sites. Two reef fish species, Acanthurus triostegus and Zanclus cornutus, were 10% smaller at Upolu than at neighboring islands. Importantly, coral cover was higher within marine protected areas, indicating that local management action remains a useful tool to support the resilience of local reef ecosystems to anthropogenic impacts. This study may be interpreted as cautionary sign for reef ecosystem health in remote locations on this planet, reinforcing the need to immediately reduce anthropogenic impacts on a global scale.

Introduction

Coral reefs are immediately threatened by the impacts of global climate change (Hoegh-Guldberg et al., 2007). Projected increases in severity of tropical storms will probably physically devastate coral reef ecosystems (Webster et al., 2005). In addition global warming and increasing seawater temperatures are the main cause for coral bleaching, which is the disruption of the symbiosis between the coral animal and its endosymbiotic algae (Hoegh-Guldberg et al., 2007; Hughes et al., 2003). Coral bleaching can lead to the mortality of the coral host and the degradation of entire coral reef ecosystems (Graham et al., 2006). The El Niño Year 2015/2016 was declared as the “Third Global Coral Bleaching Event” and hot seawater temperatures in 2017 caused widespread coral bleaching during three consecutive years.

Much data has been collected on the status of well-known reef areas, such as the Great Barrier Reef that has been heavily impacted by climate change (De′ath et al., 2012; Hughes et al., 2017). The status of coral reefs in more remote locations, such as the small island states in the Pacific, is less well understood and regular monitoring data on reef health from these locations is often wanting. At the same time, small island populations largely rely on intact coral reef ecosystems, as they directly live from coral reef fisheries, tourism, and coastal protection.

The Tara Pacific Expedition visited the island of Upolu, Independent State of Samoa in the South West Pacific from Nov. 29 to Dec. 03, 2016 to conduct a sampling campaign of hard corals, fish, and coral reef water. Given the extent of the damage observed on the reefs, it was decided to complete a comprehensive survey of Upolu′s reef health. During this time, 83 km of coastal coral reefs were surveyed, the results of which are reported herein.

Section snippets

Literature review of disturbance history

Scientific literature and reports (“grey literature”) provided by the Samoa Ministry of Natural Resources and Environment were searched for information on the disturbance history of coral reef ecosystems at Upolu with a focus on storm damage, outbreaks of coral-eating crown-of-thorns starfish (COTS), unsustainable use of resources, land-based pollution, and coral bleaching.

Fish sampling

As part of the Tara Pacific Expedition, two species of reef fish, Acanthurus triostegus and Zanclus cornutus, were sampled

Disturbance history of Upolu

Upolu has repeatedly been hit by tropical cyclones that devastated the livelihood of the island′s inhabitants and caused physical damage to coral reef ecosystems. In 1990 cyclone Ofa and 18 months later cyclone Val heavily affected coral reefs on Upolu′s north coast and some areas on the west and southwest coast while the east and south coast remained largely unaffected (Zann and Bell, 1991). In 2004, cyclone Heta hit reefs in the central Pacific and likely also Upolu, but its effect on the

Conclusions

Coral reef ecosystems of Upolu have been subjected to repeated severe disturbances, such as tropical storms, outbreaks of coral-eating starfish (COTS), and possibly coral bleaching. In addition, many local stressors further impact coastal ecosystems at Upolu. Zann (1994) summarized the main local man-made threats to Upolu′s marine ecosystem as: overfishing, land reclamation (habitat loss), sedimentation, nutrient input, and pollution (toxic chemicals, rubbish, wastewater). Many of these

Acknowledgements

This project has been funded through the Tara consortium, France Genomique grant number ANR-10-INBS-09, and KAUST baseline and KAUST BESE division funds to CRV. Tara Pacific consortium acknowledgement: We are keen to thank the commitment of the people and the following institutions and sponsors who made this singular expedition possible: CNRS, CSM, PSL, KAUST, Genoscope/CEA, ANR-CORALGENE, France Genomique (specifically grant number ANR-10-INBS-09), agnès b., the Veolia Environment Foundation,

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