Overview

Distribution

Range Description

This species occurs in the Red Sea and the Gulf of Aden, and the southwest and northern Indian Ocean.

Red Sea
The northern Red Sea from Rabigh to the Sinai Peninsula escaped most of the bleaching and the mortality of the last couple of decades. Destroyed and critical reefs are only 6% of the total (Wilkinson, 2004) because of its high latitude and very deep water extending close to shore, and wind induced upwelling. If these factors continue they are likely to contribute to survival of northern Red Sea species into the future. The southern Red Sea did not escape recent bleaching events and the Gulf of Aqaba and the Hurghada regions are affected by numerous direct impacts from coastal development and industry.

Genetics studies have, however, demonstrated the wide degree of differentiation of Red Sea populations from other Indian Ocean and Indo-West Pacific populations, consistent with a low level of gene exchange between the Red Sea and elsewhere. This relative isolation means that recovery following regional scale disturbance that decimates populations in the Red Sea may be compromised. For Red Sea endemics such disturbances would prove catastrophic.
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Ecology

Habitat

Habitat and Ecology

Habitat and Ecology
This species occurs on shallow rocky foreshores and reefs. This species is found from 1-15 m depth.

General genus information: throughout its range, Acropora can be found on any stretch of reef and is often the dominant coral, especially along the reef front. Staghorn and plate forms flourish in sheltered areas, whereas clusters and semi-massive types can withstand more exposed conditions. Species that occur from the reef top to the reef slope become gradually more flattened with depth (Wood 1983).

Systems
  • Marine
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Conservation

Conservation Status

IUCN Red List Assessment


Red List Category
NT
Near Threatened

Red List Criteria

Version
3.1

Year Assessed
2008

Assessor/s
Aeby, G., Delbeek, J.C., Lovell, E., Richards, Z., Reboton, C. & Bass, D.

Reviewer/s
Livingstone, S., Polidoro, B. & Smith, J. (Global Marine Species Assessment)

Contributor/s

Justification
This species is found in the Red Sea and west Indian Ocean and is common in the majority of its range. It is particularly susceptible to bleaching, disease, crown-of-thorns starfish predation and extensive reduction of coral reef habitat due to a combination of threats. Specific population trends are unknown but population reduction can be inferred from declines in habitat quality based on the combined estimates of both destroyed reefs and reefs at the critical stage of degradation within its range (Wilkinson 2004). Its threat susceptibility increases the likelihood of being lost within one generation in the future from reefs at a critical stage. Therefore, the estimated habitat degradation and loss of 22% over three generation lengths (30 years) is the best inference of population reduction. Due to the susceptibility of this species to bleaching, and is close to the threshold for a threatened category it is listed as Near Threatened. It will be important to reassess this species in 10 years time because of predicted threats from climate change and ocean acidification.
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Population

Population
This species is common in the western Indian Ocean, and it is uncommon elsewhere.

There is no species specific population information available for this species. However, there is evidence that overall coral reef habitat has declined, and this is used as a proxy for population decline for this species. This species is particularly susceptible to bleaching, disease, and other threats and therefore population decline is based on both the percentage of destroyed reefs and critical reefs that are likely to be destroyed within 20 years (Wilkinson 2004). We assume that most, if not all, mature individuals will be removed from a destroyed reef and that on average, the number of individuals on reefs are equal across its range and proportional to the percentage destroyed reefs. Reef losses throughout the species' range have been estimated over three generations, two in the past and one projected into the future.

The age of first maturity of most reef building corals is typically three to eight years (Wallace 1999) and therefore we assume that average age of mature individuals is greater than eight years. Furthermore, based on average sizes and growth rates, we assume that average generation length is 10 years, unless otherwise stated. Total longevity is not known, but likely to be more than ten years. Therefore any population decline rates for the Red List assessment are measured over at least 30 years. Follow the link below for further details on population decline and generation length estimates.

Population Trend
Decreasing
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Threats

Major Threats
Members of this genus have a low resistance and low tolerance to bleaching and disease, and are slow to recover.

Acanthaster planci, the crown-of-thorns starfish, has been observed preferentially preying upon corals of the genus Acropora (Colgan 1987). This growth form is moderately susceptible to predation by COTS. Crown-of-thorns starfish (COTS) (Acanthaster planci) are found throughout the Pacific and Indian Oceans, and the Red Sea. These starfish voracious predators of reef-building corals, with a preference for branching and tabular corals such as Acropora species. Populations of the crown-of-thorns starfish have greatly increased since the 1970s and have been known to wipe out large areas of coral reef habitat. Increased breakouts of COTS has become a major threat to some species, and have contributed to the overall decline and reef destruction in the Indo-Pacific region. The effects of such an outbreak include the reduction of abundance and surface cover of living coral, reduction of species diversity and composition, and overall reduction in habitat area.

In general, the major threat to corals is global climate change, in particular, temperature extremes leading to bleaching and increased susceptibility to disease, increased severity of ENSO events and storms, and ocean acidification.

Coral disease has emerged as a serious threat to coral reefs worldwide and a major cause of reef deterioration (Weil et al. 2006). The numbers of diseases and coral species affected, as well as the distribution of diseases have all increased dramatically within the last decade (Porter et al. 2001, Green and Bruckner 2000, Sutherland et al. 2004, Weil 2004). Coral disease epizootics have resulted in significant losses of coral cover and were implicated in the dramatic decline of acroporids in the Florida Keys (Aronson and Precht 2001, Porter et al. 2001, Patterson et al. 2002). In the Indo-Pacific, disease is also on the rise with disease outbreaks recently reported from the Great Barrier Reef (Willis et al. 2004), Marshall Islands (Jacobson 2006) and the northwestern Hawaiian Islands (Aeby 2006). Increased coral disease levels on the GBR were correlated with increased ocean temperatures (Willis et al. 2007) supporting the prediction that disease levels will be increasing with higher sea surface temperatures. Escalating anthropogenic stressors combined with the threats associated with global climate change of increases in coral disease, frequency and duration of coral bleaching and ocean acidification place coral reefs in the Indo-Pacific at high risk of collapse.

Localized threats to corals include fisheries, human development (industry, settlement, tourism, and transportation), changes in native species dynamics (competitors, predators, pathogens and parasites), invasive species (competitors, predators, pathogens and parasites), dynamite fishing, chemical fishing, pollution from agriculture and industry, domestic pollution, sedimentation, and human recreation and tourism activities.

The severity of these combined threats to the global population of each individual species is not known.
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Management

Conservation Actions

Conservation Actions
All corals are listed on CITES Appendix II. Parts of the species’ range fall within Marine Protected Areas.

Recommended measures for conserving this species include research in taxonomy, population, abundance and trends, ecology and habitat status, threats and resilience to threats, restoration action; identification, establishment and management of new protected areas; expansion of protected areas; recovery management; and disease, pathogen and parasite management. Artificial propagation and techniques such as cryo-preservation of gametes may become important for conserving coral biodiversity.

Having timely access to national-level trade data for CITES analysis reports would be valuable for monitoring trends this species. The species is targeted by collectors for the aquarium trade and fisheries management is required for the species, e.g., MPAs, quotas, size limits, etc. Consideration of the suitability of species for aquaria should also be included as part of fisheries management, and population surveys should be carried out to monitor the effects of harvesting.
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