Taxonomic Notes
This species was previously considered an ecotype of Porites panamensis but is now valid as a separate species (López-Pérez et al. 2003).
Justification
This free-living coral species has a restricted range in the Gulf of California, Mexico. It is rare, associates with rhodolith beds and has a narrow thermal tolerance. It has declined by more than 90% since the early 1990s, or over the past three generations (about 30 years) due to impacts from hurricanes and bleaching events and is now only extant in three areas. As strong El Niño-Southern Oscillation (ENSO) events have increased in frequency and the water temperature is gradually warming in the Gulf of California, it is inferred that declines will continue in the future. The estimated extent of occurrence (EOO) is 4,766 km2 and the estimated area of occupancy (AOO) is 12 km2. The species qualifies for Endangered under Criterion B and Critically Endangered under Criterion A. It is therefore listed as Critically Endangered A2bce with a recommendation to develop conservation strategies to avoid extinction.
Geographic Range Information
This species is endemic to the Gulf of California, Mexico (Reyes-Bonilla 2002, Paz-García and Balart 2016, Martínez‑Castillo et al. 2020). This range restriction may be linked to its physiological limit of temperature tolerance (Paz-García and Balart 2016). Historically, the species ranged from Islas Marias north to Isla Angel de la Guarda (an area of 15,552 km2) but now is extant in only three sites in the southwestern Gulf of California covering an area of 891 km2: one at San Lorenzo Channel in La Paz Bay, Isla Catalana in Loreto Bay and El Requeson Beach in Concepcion Bay (Paz-García and Balart 2016, Martínez‑Castillo et al. 2020).
The depth range is 1-40 m but primarily occurs deeper than 20 m (López-Pérez et al. 2003).
Based on a minimum convex polygon drawn around the extent of its extant range, the estimated extent of occurrence (EOO) is 4,766 km2. Based on a 2x2 km grid overlaid on the nine extant localities, the estimated area of occupancy (AOO) is 12 km2. The number of locations is three based on the pervasive threat from increasing bleaching events and severe storms.
Population Information
This species is rare in general (Reyes-Bonilla 2002, López-Pérez 2013, Martínez‑Castillo et al. 2020). It was reported from Cabo San Lucas in the early 1980s, but the local populations have since become extinct (López-Pérez et al. 2003). Live populations were reported from Loreto (Baja California Sur) and from Bahia de Banderas (Jalisco) previous to 2008 (H. Reyes-Bonilla pers. comm. 2008). This species' population has rapidly and severely declined since the early 1990s in both the northern and southern parts of its range and currently occurs in less than 6% of its historical range, which represents a >90% decline over the past three generations, or about 30 years (Martínez‑Castillo et al. 2020). The cause of these declines is related to water temperatures extremes due to strong El Niño-Southern Oscillation (ENSO) events, particularly in 1982 and 2010 (Paz-García and Balart 2016). At least in the few extant populations, it appears to have some resiliency as successful reproductions was documented even during the strong ENSO event of 2014-2015 (Martínez‑Castillo et al. 2020). In 2014-2015, 355 adult colonies were sampled from Isla Catalana and this site represented a higher density of coral colonies (>70 colonies per m2) as compared to the other two extant populations (Martínez‑Castillo et al. 2020). Despite these severe declines, the species was found to have high genetic variability (Martínez-Castillo et al. 2018).
Habitat and Ecology Information
This species inhabits protected rock rubble substrates (Veron et al. 2016, Glynn et al. 2017). It is a free-living coral that has a small colony size, does not attach to the substratum and typically associates with rhodolith beds (Martínez‑Castillo et al. 2020). It has a gonochoristic brooding reproductive strategy with asynchronous gamete development regulated by sea surface temperature and light and reaches maturity at a relatively early age (Martínez‑Castillo et al. 2020).
The age at first maturity of most reef-building corals is typically three to eight years (Wallace 1999). Based on this, we infer that the average age of mature individuals of this species is greater than eight years. Based on average sizes and growth rates, we also infer that the average length of one generation is 10 years. Longevity is not known, but is likely to be greater than 10 years. Therefore, any population decline rates estimated for the purposes of this Red List assessment are measured over a time period of 30 years.
Threats Information
The severe decline of this species is due to impacts from hurricanes and bleaching events (Paz-García and Balart 2016, Martínez‑Castillo et al. 2020). The unbranching species in this genus are not particularly susceptible to bleaching, but are more prone to disease than many other corals. Coral bleaching during strong ENSO events is one of the most severe impacts to the marine environment of the Gulf of California (Páez-Osuna et al. 2016). In the Gulf of California from 2010-2020, temperatures gradually warmed by an average of 1◦C and the frequency of extreme marine heatwaves increased threefold and this has caused shifts in the reef communities that this species is dependent on (Favoretto et al. 2022).
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 (Richards et al. 2008). The most recent, and first, multi-year, global bleaching event (spanning hundreds of kilometers or more) was from 2014 to 2017. Nearly 30% of reefs suffered mortality level-stress, more than 50% of affected reef areas were impacted at least twice, and some localities saw almost complete coral cover loss (Blunden et al. 2018, Vargas-Angel et al. 2019, Eakin et al. 2019). The average interval between bleaching events is now more than 50% less than before, preventing full reef recovery (Hughes et al. 2018).
Coral disease has emerged as a serious threat to coral reefs worldwide with increases in numbers of diseases, coral species affected, and geographic extent (Ward et al. 2004, Sutherland et al. 2004, Sokolow et al. 2009). Outbreaks of coral diseases have damaged coral reefs worldwide with the most widespread, virulent, and longest running coral disease outbreak currently occurring on the Florida Reef Tract and throughout the Caribbean. The disease, stony coral tissue loss disease, has been ongoing since 2014 (Precht et al. 2016) and has devastated affected reefs along Florida (Walton et al. 2018, Williams et al. 2021) and throughout the Caribbean (Alvarez-Filip et al. 2019, Kramer et al. 2019). Numerous disease outbreaks have also occurred in the Indo-Pacific (Willis et al. 2004, Aeby et al. 2011; 2016), Indian Ocean (Raj et al. 2016) and Persian Gulf (Howells et al. 2020). 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 (Richards et al. 2008). However, more than 60% of the world’s reefs are immediately threatened by local pressures (Bridge et al. 2013).
Use and Trade Information
Conservation Actions Information
This species listed as “in risk of extinction” in the Mexican Federal Law for species protection NOM-059-SEMARNAT-2010 (Martínez‑Castillo et al. 2020). The development of strategies that prevent the negative effects of both climate change and local threats are needed for this species (Martínez‑Castillo et al. 2020).
All stony corals are listed on CITES Appendix II. All stony corals (Scleractinia) fall under Annex B of the European Union Wildlife Trade Regulations, and have done so since 1997. Furthermore, several countries (India, Israel, Somalia, Djibouti, Solomon Islands and the Philippines) at various stages have banned either the trade or export of CITES II listed species, which includes all stony corals, since 1999.
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.
The Convention on Biological Diversity adopted an updated Strategic Plan for Biodiversity 2011–2020, which now includes Aichi Biodiversity Target 11, calling for 10% of coastal and marine areas to be conserved by 2020. And in 2016, the IUCN World Conservation Congress agreed upon a target of >30% global marine protection by 2030.
It is crucial that global warming is constrained well below 2°C (the goals of the Paris Agreement).
