Effects of moderate thermal anomalies on Acropora corals around Sesoko Island, Okinawa
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Abstract:
Over the past several decades, coral reef ecosystems have experienced recurring bleaching events. These events were predominantly caused by thermal anomalies, which vary widely in terms of severity and spatio-temporal distribution. Acropora corals, highly prominent contributors to the structural complexity of Pacific coral reefs, are sensitive to thermal stress. Response of Acropora corals to extremely high temperature has been well documented. However, studies on the effects of moderately high temperature on Acropora corals are limited. In the summer of 2016, a moderate coral bleaching event due to moderately high temperature was observed around Sesoko Island, Okinawa, Japan. The objective of this study was to examine thermal tolerance patterns of Acropora corals, across reefs with low to moderate thermal exposure (degree heating weeks ~2-5°C week). Field surveys on permanent plots were conducted from October 2015 to April 2017 to compare the population dynamics of adult Acropora corals 6 months before and after the bleaching events around Sesoko Island. Variability in thermal stress response was driven primarily by the degree of thermal stress. Wave action and turbidity may have mediated the thermal stress. Tabular and digitate coral morphologies were the most tolerant and susceptible to thermal stress, respectively. Growth inhibition after bleaching was more pronounced in the larger digitate and corymbose coral morphologies. This study indicates that Acropora populations around Sesoko Island can tolerate short-term, moderate thermal challenges.Keywords:
Acropora
Coral bleaching
Scleractinia
Anthozoa
Porites
Scleractinia
Anthozoa
Porites
Panama
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Scleractinia
Anthozoa
Porites
Lobata
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Porites
Scleractinia
Anthozoa
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Coral spawning in the northern Gulf of Aqaba has been reported to be asynchronous, making it almost unique when compared to other regions in the world. Here, we document the reproductive condition of Acropora corals in early June 2014 in Dahab, in the Gulf of Aqaba, 125 km south of previous studies conducted in Eilat, Israel. Seventy-eight percent of Acropora colonies from 14 species had mature eggs, indicating that most colonies will spawn on or around the June full moon, with a very high probability of multi-species synchronous spawning. Given the proximity to Eilat, we predict that a comparable sampling protocol would detect similar levels of reproductive synchrony throughout the Gulf of Aqaba consistent with the hypothesis that high levels of spawning synchrony are a feature of all speciose coral assemblages.
Scleractinia
Anthozoa
Acropora
Spawn (biology)
Harem
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The hermatypic coral fauna of the Western Indian Ocean is one of the least known globally. This is true of the East African Coast and especially Mozambique, where taxonomic studies are scarce and date mostly from decades ago. The morphology of coral species is subjected to a high level of geographical and environmental variability, which leads to difficulties in field identification and may limit the level of taxonomic resolution at which coral studies can be conducted. Thorough examination of collected specimens can provide more reliable identification of species and more importantly provide a physical record that can be studied further. We collected and identified 32 species of corals from the genus Acropora (Anthozoa: Scleractinia: Acroporidae) of Vamizi Island, northern Mozambique, and present an annotated and illustrated checklist of species. These species records illustrate the high diversity of Acropora in Vamizi, which is comparable to the diversity of this genus in the region. This study can help assess the biodiversity of the region and provides a baseline against which changes can be closely monitored.
Scleractinia
Acropora
Anthozoa
Hermatypic coral
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Manta tows in fringing and barrier reef areas, together with observations, were used to estimate the extent of the bleaching and associated coral mortality in Mayotte between 1 and 24 of May 2010. Three areas around the island were surveyed. The results from fringing reefs in the north coast of Mayotte showed that nearly 80 % of coral benthos was either bleached or dead (covered with thin algal overgrowth), while 50 % and 35 % of coral was bleached or dead in the two other surveyed areas, highlighting this as a considerable bleaching event. The observations showed spatial and temporal heterogeneity in the extent of the bleaching and mortality. The most genera most susceptible to bleaching were Pocillopora and tabular Acropora , while Porites seemed to have suffered the least. Our observations of bleached genera were consistent with those of the 1997-1998 bleaching event.
Acropora
Porites
Coral bleaching
Fringing reef
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The purpose of this application is to conserve the names of four genera of scleractinian corals: Porites Link, 1807, Galaxea Oken, 1815, Mussa Oken, 1815 and Dendrophyllia Blainville, 1830.The names Galaxea and Mussa are in current use for Indo-Pacific and Caribbean genera respectively but are formally unavailable because vol. 3 (Zoologie) of Oken's (1815-1816) work Lehrbuch der Naturgeschichte, in which the names were published, has been rejected for nomenclatural purposes (Opinion 417, September 1956).The name Porites Link is in universal use for a widely distributed reef-building coral but is threatened by the senior homonym Porites Cuvier, 1798.The names Galaxea, Mussa and Dendrophyllia (a predominantly deep-water non-reef-building genus) are also threatened by Porites Cuvier as a senior subjective synonym.
Scleractinia
Anthozoa
Porites
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BackgroundClimate-induced coral bleaching poses a major threat to coral reef ecosystems, mostly because of the sensitivities of key habitat-forming corals to increasing temperature. However, susceptibility to bleaching varies greatly among coral genera and there are likely to be major changes in the relative abundance of different corals, even if the wholesale loss of corals does not occur for several decades. Here we document variation in bleaching susceptibility among key genera of reef-building corals in Moorea, French Polynesia, and compare bleaching incidence during mass-bleaching events documented in 1991, 1994, 2002 and 2007. Methodology/Principal FindingsThis study compared the proportion of colonies that bleached for four major genera of reef-building corals (Acropora, Montipora, Pocillopora and Porites), during each of four well-documented bleaching events from 1991 to 2007. Acropora and Montipora consistently bleached in far greater proportions (up to 98%) than Pocillopora and Porites. However, there was an apparent and sustained decline in the proportion of colonies that bleached during successive bleaching events, especially for Acropora and Montipora. In 2007, only 77% of Acropora colonies bleached compared with 98% in 1991. Temporal variation in the proportion of coral colonies bleached may be attributable to differences in environmental conditions among years. Alternately, the sustained declines in bleaching incidence among highly susceptible corals may be indicative of acclimation or adaptation. Conclusions/SignificanceCoral genera that are highly susceptible to coral bleaching, and especially Acropora and Montipora, exhibit temporal declines in their susceptibility to thermal anomalies at Moorea, French Polynesia. One possible explanation for these findings is that gradual removal of highly susceptible genotypes (through selective mortality of individuals, populations, and/or species) is producing a coral assemblage that is more resistant to sustained and ongoing ocean warming.
Acropora
Coral bleaching
Porites
Anthozoa
Pocillopora damicornis
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Spawning Red SeaReef-building scleractinian corals proliferate and maintain their populations, in part, through sexual reproduction.They typically reproduce sexually as either gonochoric (separate male and female) or hermaphroditic (producing both eggs and sperm) colonies.Both types of sexual reproduction achieved as spawning processes that take place once a year and this process affected by environmental conditions such as temperature, photoperiod and pH level.In relation, the current study was designed to explore the reproduction patterns of two Acroporoid coral species; Acropora digitifera and Acropora gemmifera, which inhabiting the northern Red Sea (Hurghada, Egypt).A scanning electron microscope (SEM) was used to identify both coral species and to obtain their microstructure details.For reproduction study purpose, gonads maturity status and spawning timing of both studied species were noticed, either by direct field observations, during the study period including two consecutive spawning seasons, or observed in aquaria, by taking live coral colony samples for watching their specific spawning release.Results indicated that both investigated species are hermaphroditic broadcasting spawner (release buoyant egg-sperm bundles) and showed gradual gonads maturity development begin from October until their spawning time in late April.All polyps became empty from egg sperm bundles in early May.There was a clear relationship between the spawning time of the two coral species and the lunar cycle, temperature, and photoperiod.Spawning of study species occurred on nights (nearly 3-4 hours after sunset) during the new moon and full moon phases.The present study concluded that A. digitifera and A. gemmifera spawned before April full moon within two days.
Acropora
Scleractinia
Anthozoa
Full moon
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