Campbell, Stuart J., Pratchett, Morgan S., Anggoro, Aji W., Ardiwijaya, Rizya L, Fadli, Nur, Herdiana, Yudi, Kartawijaya, Tasrif, Mahyiddin, Dodent, Mukminin, Ahmad, Pardede, Shinta T., Rudi, Edi, Siregar, Achis M., and Baird, Andrew H. (2007) Disturbance to coral reefs in Aceh, Northern Sumatra: impacts of the Sumatra-Andaman tsunami and pre-tsunami degradation. Atoll Research Bulletin, 544. pp. 55-78.

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Abstract

The Sumatra-Andaman tsunami of 26 December 2004 was the first to occur in areas for which good ecological data existed prior to the event and consequently provided a unique opportunity to assess the effects of this type of natural disturbance in tropical marine ecosystems. Less than 100 days after the event we visited 49 sites on coral reefs in northern Aceh, Indonesia, all within 300 km of the epicentre, to determine the nature and extent of tsunami damage and pre-tsunami disturbance. Reef fish diversity and abundance were also assessed in relation to tsunami impact and existing marine resource management regulations. At these sites, the initial damage to corals, while occasionally spectacular, was surprisingly limited and trivial when compared to pre-existing damage most probably caused by destructive fishing practices. The abundance of up-turned corals was highly dependent on habitat and largely restricted to corals growing in unconsolidated substrata at depth, a feature we believe unique to tsunami disturbance. Other evidence of tsunami damage, including the abundance of broken corals and recently killed corals was patchy and varied unpredictably between sites: reef aspect, geographic location and management regime had no significant effect on these variables with the exception of broken live corals which were more abundant at locations where the tsunami was larger. Interestingly, there was little correlation between damage variables, suggesting the type of damage observed was strongly influenced by which corals were present at a particular site or depth. In contrast, reef condition was clearly correlated with the management regime. Coral cover was on average 2-3 times higher on reefs managed under the traditional Acehnese system, Panglima Laut, and in the Pulau Rubiah Marine Park when compared to open access areas. Turf algae and coral rubble were 2-3 times more abundant in open access sites compared with managed areas. These results are consistent with a history of destructive fishing practices, such as bombing and cyanide fishing in open access areas. Coral reef fish abundance and diversity did not differ among management zones, despite the fact that Pulau Rubiah Marine Park has been closed to fishing for 10 years. However, there were consistent differences in the structure of the reef fish assemblages among these zones. For example, the near absence of chaetodontids at open access sites is probably the result of low coral cover. The high abundance of scarids and acanthurids in the Marine Park, suggests that while management efforts have failed to allow fish to increase in abundance, they have been effective at protecting certain species. The tsunami had no detectable affect on reef fish assemblages at these sites. This lack of major damage means that neither the conservation priorities nor the risks to reefs have been changed by the tsunami and it is vitally important that resources are not directed to short term, small scale, rehabilitation programs which will not reverse long term declines in reef condition which were evident at many of our sites.

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