Threats listed in assessment
In the Gulf, the major threats to corals include extreme and increasing temperature variability due to climate change, as well as direct destruction and increased turbidity caused by coastal construction (Riegl et al. 2012). Although bleaching thresholds in the Gulf are the highest recorded in the world (Riegl et al. 2012), bleaching events in the UAE have resulted in significant mortality (such as in 1996-1998, 2002, 2010 and 2017) and slow recovery (Burt et al. 2008). In Abu Dhabi, the most recent coral bleaching event resulted in nearly 95% of corals bleaching, and by April 2018, mortality reached 73% (Burt et al. 2019). This event resulted in mass mortality of even the more stress-tolerant corals such as poritids and merulinids (Burt et al. 2019). Coastal development, particularly large-scale offshore real estate developments and sedimentation associated with reclamation, has directly buried coral reefs in the Gulf (Burt et al. 2008, 2013; Burt 2014; Burt and Bartholomew 2019). In the Sea of Oman, UAE reefs have experienced major hurricanes and harmful algal blooms that caused high coral mortality and shifted community structure (Bauman et al. 2010, Foster et al. 2011).Globally, 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. This species experienced localized population declines after El Niño events (for example, Española Island, Galapagos: Glynn 1997 and Manuel Antonio and Punta Cambial, Costa Rica: Jiménez and Cortés 2001, 2003). However, it is more resistant to bleaching than shallow-water corals such as Pocillopora (Feingold 1996). In some localities, species of Psammocora were overgrown by algae after a bleaching event. For example, large aggregations of this species were overgrown by thick mats of Caulerpa after the 1982-1983 El Niño event in Panama (Glynn 1997); similar overgrowth of Psammocora-dominated reefs occurred at La Penca, Costa Rica (Bernadette et al. 2006). At Manuel Antonio, Costa Rica, species of Psammocora were completely overgrown by a brown algae (Jimenez and Cortés 2001). Species of Psammocora are also negatively impacted by predation by the crown-of-thorns starfish, Acanthaster planci, and pufferfish, Arothron meleagris (Cortés and Guzmán 1998, Reyes-Bonilla et al. 1998). These voracious predators of reef-building corals are found throughout the Pacific and Indian Oceans, and the Red Sea. 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 have 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. The pufferfish, Arothron meleagris, is capable of reducing populations of Psammocora species if other preferred coral species such as Porites lobata are absent (Cortés and Guzmán 1998).Coral disease has emerged as a serious threat to coral reefs worldwide and is a major cause of reef deterioration (Weil 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 et al. 2006). Increased coral disease levels on the Great Barrier Reef were correlated with increased ocean temperatures (Willis et al. 2004) 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.