The most severe and large scale-bleaching event on record occurred in 1998 world-wide. In Mauritius, three surveys covering 2 habitats at 4-5 sites were conducted to describe and quantify the event. Bleaching was recorded at all sites and habitats. However, relatively few corals were bleached (<10%) except at one localised site (Le Bouchon: 38.6%) indicating that Mauritius was one of the few islands in the Indian Ocean to have sustained a comparatively mild bleaching episode. On the reef flat Acropora species were generally more susceptible to bleaching than non-Acropora species. In contrast on the reef slopes, non-Acropora species were more affected than the Acropora species. Furthermore, susceptibility to bleaching differed within colonies and species. The main cause of this bleaching event was most likely due to an increase in seawater temperature and solar radiation, exacerbated by lowered salinity from higher seasonal rainfall.
{"title":"The extent and intensity of the 1998 mass bleaching event on the reefs of Mauritius, Indian Ocean","authors":"R. M. Pillay, H. Terashima, Hiroyuki Kawasaki","doi":"10.3755/JCRS.2002.43","DOIUrl":"https://doi.org/10.3755/JCRS.2002.43","url":null,"abstract":"The most severe and large scale-bleaching event on record occurred in 1998 world-wide. In Mauritius, three surveys covering 2 habitats at 4-5 sites were conducted to describe and quantify the event. Bleaching was recorded at all sites and habitats. However, relatively few corals were bleached (<10%) except at one localised site (Le Bouchon: 38.6%) indicating that Mauritius was one of the few islands in the Indian Ocean to have sustained a comparatively mild bleaching episode. On the reef flat Acropora species were generally more susceptible to bleaching than non-Acropora species. In contrast on the reef slopes, non-Acropora species were more affected than the Acropora species. Furthermore, susceptibility to bleaching differed within colonies and species. The main cause of this bleaching event was most likely due to an increase in seawater temperature and solar radiation, exacerbated by lowered salinity from higher seasonal rainfall.","PeriodicalId":432348,"journal":{"name":"Journal of The Japanese Coral Reef Society","volume":"2002 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2002-10-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129735426","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
While spawning and planula release are known to occur during night time in the majority of coral species, a species endemic to high latitude of Japan and Korea, Alveopora japonica, was found to release planulae during daytime. Laboratory experiments were conducted to see how light affects planula release in this species. Under the natural light condition in the laboratory A. japonica released planulae between 07:00 and 12:00 in the morning. When the timing of exposure to light was changed, planulation also shifted and coincided with the time of light exposure irrespective of the actual time of day. When the colonies were exposed to light twice a day, i.e. in the morning and evening, all colonies released planulae only in the morning. Direct observation on planulating polyps showed that polyps elongated before planulation and such polyp elongation occurred only under the light condition. Consequently, it is concluded that light is a proximate factor which governs planula release through polyp elongation in A. ja-
{"title":"Experimental analysis of planula release in a scleractinian coral Alveopora japonica","authors":"Thamrin, S. Nojima, M. Tokeshi","doi":"10.3755/JCRS.2001.25","DOIUrl":"https://doi.org/10.3755/JCRS.2001.25","url":null,"abstract":"While spawning and planula release are known to occur during night time in the majority of coral species, a species endemic to high latitude of Japan and Korea, Alveopora japonica, was found to release planulae during daytime. Laboratory experiments were conducted to see how light affects planula release in this species. Under the natural light condition in the laboratory A. japonica released planulae between 07:00 and 12:00 in the morning. When the timing of exposure to light was changed, planulation also shifted and coincided with the time of light exposure irrespective of the actual time of day. When the colonies were exposed to light twice a day, i.e. in the morning and evening, all colonies released planulae only in the morning. Direct observation on planulating polyps showed that polyps elongated before planulation and such polyp elongation occurred only under the light condition. Consequently, it is concluded that light is a proximate factor which governs planula release through polyp elongation in A. ja-","PeriodicalId":432348,"journal":{"name":"Journal of The Japanese Coral Reef Society","volume":"14 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2001-12-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127205949","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Organic carbon production (photosynthesis-respiration) and inorganic carbon production (calcification-dissolution) of two massive scleractinian corals, Favites sp. and Porites sp., were measured in a mesocosm, at the early and late stages of the 1998 coral bleaching event. Air-sea CO2 flux was also measured directly on the surface of seawater, and carbon budgets were calculated from these measurements. Net organic carbon production was 15.8 mmol C m-2 d-1 at the early stage of coral bleaching and decreased to 9.5 mmol C m-2 d-1 at the late stage of coral bleaching. Net inorganic carbon production also decreased drastically from 11.2 mmol C m-2 d-1 at the early stage to -7.0 mmol C m-2 d-1 at the late stage of coral bleaching, which was caused by the decrease in calcification in the daytime and increase in the dissolution of carbonate at night. Air-sea CO2 fluxes were -1.8 mmol m-2 d-1 at the early stage and -1.1 mmol m 2 d 1 at the late stage, respectively, which indicates absorption of CO2 from air to seawater. The gross primary production/respiration ratio (=1.2) at the early and late stages of bleaching was nearly constant, which suggested that the biological activity of zooxanthellae does not alter significantly at the late stage of coral bleaching. The calcification rate was remarkably reduced compared to photosynthesis. Coral bleaching severely damaged on the physiological activities of corals, and had a large effect on the carbon metabolism in coral-algal symbiosis.
在1998年珊瑚白化事件的早期和后期，测量了两种块状硬核珊瑚(Favites sp.)和Porites sp.)的有机碳产量(光合作用-呼吸作用)和无机碳产量(钙化-溶解)。还直接在海水表面测量了大气-海洋CO2通量，并根据这些测量结果计算了碳收支。净有机碳产量在珊瑚白化初期为15.8 mmol C m-2 d-1，在珊瑚白化后期降至9.5 mmol C m-2 d-1。净无机碳产量也从早期的11.2 mmol C m-2 d-1急剧下降到后期的-7.0 mmol C m-2 d-1，这是由于白天钙化减少，晚上碳酸盐溶解增加所致。海气CO2通量前期为-1.8 mmol m-2 d-1，后期为-1.1 mmol m-2 d-1，表明CO2从空气中吸收到海水中。珊瑚白化初期和后期的总初级产量/呼吸比(=1.2)基本不变，表明虫黄藻的生物活性在珊瑚白化后期变化不明显。与光合作用相比，钙化率显著降低。珊瑚白化严重破坏了珊瑚的生理活动，并对珊瑚-藻共生中的碳代谢产生了较大的影响。
{"title":"Change of coral carbon metabolism influenced by coral bleaching","authors":"H. Fujimura, T. Oomori, T. Maehira","doi":"10.3755/JCRS.2001.41","DOIUrl":"https://doi.org/10.3755/JCRS.2001.41","url":null,"abstract":"Organic carbon production (photosynthesis-respiration) and inorganic carbon production (calcification-dissolution) of two massive scleractinian corals, Favites sp. and Porites sp., were measured in a mesocosm, at the early and late stages of the 1998 coral bleaching event. Air-sea CO2 flux was also measured directly on the surface of seawater, and carbon budgets were calculated from these measurements. Net organic carbon production was 15.8 mmol C m-2 d-1 at the early stage of coral bleaching and decreased to 9.5 mmol C m-2 d-1 at the late stage of coral bleaching. Net inorganic carbon production also decreased drastically from 11.2 mmol C m-2 d-1 at the early stage to -7.0 mmol C m-2 d-1 at the late stage of coral bleaching, which was caused by the decrease in calcification in the daytime and increase in the dissolution of carbonate at night. Air-sea CO2 fluxes were -1.8 mmol m-2 d-1 at the early stage and -1.1 mmol m 2 d 1 at the late stage, respectively, which indicates absorption of CO2 from air to seawater. The gross primary production/respiration ratio (=1.2) at the early and late stages of bleaching was nearly constant, which suggested that the biological activity of zooxanthellae does not alter significantly at the late stage of coral bleaching. The calcification rate was remarkably reduced compared to photosynthesis. Coral bleaching severely damaged on the physiological activities of corals, and had a large effect on the carbon metabolism in coral-algal symbiosis.","PeriodicalId":432348,"journal":{"name":"Journal of The Japanese Coral Reef Society","volume":"50 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2001-12-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133027290","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Three types of symbiotic dinoflagellates L (large), B (brown) and G (green) found in hermatypic corals from a fringing reef of Sesoko Island (Okinawa, Japan) differed morphologically, physiologically and biochemically. Colonies of the hydrocoral Millepora intricata hosted symbionts of type L only; scleractinian corals containing type B only were Pocillopora damicornis, type G only were Seriatopora caliendrum and S. hystrix, and both types B and G were found living together in Stylophora pistillata and Echinopora lamellosa. The symbiotic dinoflagellates (SD) differed considerably in cell size, shape and structural elements in coccoid state in hospite. SD of these types also differed in photosynthetic capacities, primary production, pigment accumulation and maximum rates of cell division and degradation.Corals hosting various types of SD significantly differed in light-resistance. Scleractinian corals with symbionts of both types B and G, in the same colony, acclimated to bright light by increasing the relative number of symbionts of type G and acclimated to dim light by increasing the SD number of type B. It was shown that scleractinian corals can photo-acclimate through formation of optimal composition of SD types under various light intensities.
{"title":"Morphophysiological variations of symbiotic dinoflagellates in hermatypic corals from a fringing reef at Sesoko Island","authors":"E. Titlyanov, T. Titlyanova, A. Amat, K. Yamazato","doi":"10.3755/JCRS.2001.51","DOIUrl":"https://doi.org/10.3755/JCRS.2001.51","url":null,"abstract":"Three types of symbiotic dinoflagellates L (large), B (brown) and G (green) found in hermatypic corals from a fringing reef of Sesoko Island (Okinawa, Japan) differed morphologically, physiologically and biochemically. Colonies of the hydrocoral Millepora intricata hosted symbionts of type L only; scleractinian corals containing type B only were Pocillopora damicornis, type G only were Seriatopora caliendrum and S. hystrix, and both types B and G were found living together in Stylophora pistillata and Echinopora lamellosa. The symbiotic dinoflagellates (SD) differed considerably in cell size, shape and structural elements in coccoid state in hospite. SD of these types also differed in photosynthetic capacities, primary production, pigment accumulation and maximum rates of cell division and degradation.Corals hosting various types of SD significantly differed in light-resistance. Scleractinian corals with symbionts of both types B and G, in the same colony, acclimated to bright light by increasing the relative number of symbionts of type G and acclimated to dim light by increasing the SD number of type B. It was shown that scleractinian corals can photo-acclimate through formation of optimal composition of SD types under various light intensities.","PeriodicalId":432348,"journal":{"name":"Journal of The Japanese Coral Reef Society","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2001-12-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130566798","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
In order to restore disturbed coral reefs, transplantation of coral fragments or coral heads has been conducted in many parts of the world. We reviewed methods and results of the transplantation experiments described in numerous previous reports in order to determine recommendable methodologies. Problems that should be solved by future studies are discussed. For transplantation, generally, small pieces of coral are taken from the donor colony using hammer, chisel and the like. If the collection site is far from the transplantation site, fragments should be placed in bucket full of seawater. There are various methods to fix the coral fragment onto substrate, e. g. by means of epoxy cement, plastic coated wire and nails. They should be chosen according to size and shape of coral fragments, but we found fixation with nails and cable ties is easy and reliable for staghorn corals. The cost of transplantation with a density of 245, 000 fragments per hectare secured by means of nails and cable ties has been estimated at about 36, 000, 000 JPN Yen. So far, species of the genera Acropora, Porites, Pavona and Galaxea were most frequently used for transplantation as they have relatively high survival rates.
{"title":"The review of coral transplantation around the world","authors":"Nami Okubo, M. Omori","doi":"10.3755/JCRS.2001.31","DOIUrl":"https://doi.org/10.3755/JCRS.2001.31","url":null,"abstract":"In order to restore disturbed coral reefs, transplantation of coral fragments or coral heads has been conducted in many parts of the world. We reviewed methods and results of the transplantation experiments described in numerous previous reports in order to determine recommendable methodologies. Problems that should be solved by future studies are discussed. For transplantation, generally, small pieces of coral are taken from the donor colony using hammer, chisel and the like. If the collection site is far from the transplantation site, fragments should be placed in bucket full of seawater. There are various methods to fix the coral fragment onto substrate, e. g. by means of epoxy cement, plastic coated wire and nails. They should be chosen according to size and shape of coral fragments, but we found fixation with nails and cable ties is easy and reliable for staghorn corals. The cost of transplantation with a density of 245, 000 fragments per hectare secured by means of nails and cable ties has been estimated at about 36, 000, 000 JPN Yen. So far, species of the genera Acropora, Porites, Pavona and Galaxea were most frequently used for transplantation as they have relatively high survival rates.","PeriodicalId":432348,"journal":{"name":"Journal of The Japanese Coral Reef Society","volume":"19 2 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2001-12-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126120380","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The Ryukyu Group, composed of Pleistocene reef-complex deposits that pass laterally into terrigenous sediments, crops out on Kume-jima and its adjacent islet, Ohajima, Ryukyu Islands, southwestern Japan. We propose a major revision of the previous stratigraphic scheme for the Ryukyu Group, based on new investigations, and provide a formal stratigraphic description. These Pleistocene deposits comprise the Nakandakari, Kumejima, and Torishima Formations, in ascending order, on Kume-jima. The lowest of these, the Nakandakari Formation, consists of pumice-bearing detrital limestone (<20m thick); its surface exposure is confined to the type locality, which is on the coast to the northwest of Nakandakari. The unconformably overlying Kumejima Formation exceeds 30m in thickness and is exposed in the northwestern part of Kume-jima at elevations less than ca. 50m. It is divisible into at least three units, each comprising coral limestone and overlying rhodolith, Cycloclypeus-Operculina, and detrital limestones. The Torishima Formation rests unconformably on the Kumejima Formation, and is characteristically thin (<15m thick) and composed of well-sorted detrital and coral limestones that are thought to have been deposited in a shallow lagoon (moat). The Oha Limestone is limited in its distribution to Oha-jima and consists of diagenetically altered, reddish to brownish, coral limestone. The stratigraphic relationship between limestones on Kume-jima and those on Oha-jima remains unknown, as does the geological age of these limestones. It is evident from the stratigraphic succession and configuration of lithofacies that the reefs grew in response to at least three repeated cycles of sea-level change with amplitudes of up to 80m during deposition of the Kume-jima Formation. Subsequently, a relatively small reef now assigned to the Torishima Formation grew to fringe the older reefs.
{"title":"Pleistocene coral reef deposits (the Ryukyu Group) on Kume-jima, Okinawa Prefecture, Japan","authors":"Y. Ehara, Y. Iryu, T. Nakamori, K. Odawara","doi":"10.3755/JCRS.2001.13","DOIUrl":"https://doi.org/10.3755/JCRS.2001.13","url":null,"abstract":"The Ryukyu Group, composed of Pleistocene reef-complex deposits that pass laterally into terrigenous sediments, crops out on Kume-jima and its adjacent islet, Ohajima, Ryukyu Islands, southwestern Japan. We propose a major revision of the previous stratigraphic scheme for the Ryukyu Group, based on new investigations, and provide a formal stratigraphic description. These Pleistocene deposits comprise the Nakandakari, Kumejima, and Torishima Formations, in ascending order, on Kume-jima. The lowest of these, the Nakandakari Formation, consists of pumice-bearing detrital limestone (<20m thick); its surface exposure is confined to the type locality, which is on the coast to the northwest of Nakandakari. The unconformably overlying Kumejima Formation exceeds 30m in thickness and is exposed in the northwestern part of Kume-jima at elevations less than ca. 50m. It is divisible into at least three units, each comprising coral limestone and overlying rhodolith, Cycloclypeus-Operculina, and detrital limestones. The Torishima Formation rests unconformably on the Kumejima Formation, and is characteristically thin (<15m thick) and composed of well-sorted detrital and coral limestones that are thought to have been deposited in a shallow lagoon (moat). The Oha Limestone is limited in its distribution to Oha-jima and consists of diagenetically altered, reddish to brownish, coral limestone. The stratigraphic relationship between limestones on Kume-jima and those on Oha-jima remains unknown, as does the geological age of these limestones. It is evident from the stratigraphic succession and configuration of lithofacies that the reefs grew in response to at least three repeated cycles of sea-level change with amplitudes of up to 80m during deposition of the Kume-jima Formation. Subsequently, a relatively small reef now assigned to the Torishima Formation grew to fringe the older reefs.","PeriodicalId":432348,"journal":{"name":"Journal of The Japanese Coral Reef Society","volume":"34 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2001-12-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114446488","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
A series of laboratory experiments were conducted to determine the effect of sperm dilution, egg concentration, sperm-egg contact time, and gamete aging on fertilization success in the tropical sea urchin, Echinometra mathaei. The results demonstrated that sperm dilution, sperm age, and sperm-egg contact time were sequentially the most important factors influencing fertilization success, while egg concentration was not significant over the range tested. Sperms retained their potency for more than two hours only in relatively dense sperm suspensions (≥10-4 dilution of ‘dry’ sperm) whereas they exhibited lower viability with increasing dilutions and age. In egg-sperm contact time experiments more than 80% fertilization was achieved at lower sperm dilutions (10-3-10-2) within 10 sec of mixing, while at higher sperm dilutions, longer times of contact were needed to achieve the similar fertilizations. Consequently, eggs remained in good quality for up to 3 h and there was no abnormality or adverse effects in fertilization were observed in a series of sperm dilution tested. These laboratory experiments suggest that sperm dilution and its limited longevity can play an important role in limiting the fertilization of sea urchin eggs in the field during natural spawnings. It follows, therefore, that sea urchin (E. mathaei) are under considerable selective pressures to spawn synchronously in order to generate high sperm concentrations and higher sperm-egg encounters in the water column to maximize the probability of successful fertilization.
{"title":"Effects of gamete dilution, age and contact time on fertilization success in the tropical sea urchin, Echinometra mathaei","authors":"M. Rahman, S. Rahman, T. Uehara","doi":"10.3755/JCRS.2001.1","DOIUrl":"https://doi.org/10.3755/JCRS.2001.1","url":null,"abstract":"A series of laboratory experiments were conducted to determine the effect of sperm dilution, egg concentration, sperm-egg contact time, and gamete aging on fertilization success in the tropical sea urchin, Echinometra mathaei. The results demonstrated that sperm dilution, sperm age, and sperm-egg contact time were sequentially the most important factors influencing fertilization success, while egg concentration was not significant over the range tested. Sperms retained their potency for more than two hours only in relatively dense sperm suspensions (≥10-4 dilution of ‘dry’ sperm) whereas they exhibited lower viability with increasing dilutions and age. In egg-sperm contact time experiments more than 80% fertilization was achieved at lower sperm dilutions (10-3-10-2) within 10 sec of mixing, while at higher sperm dilutions, longer times of contact were needed to achieve the similar fertilizations. Consequently, eggs remained in good quality for up to 3 h and there was no abnormality or adverse effects in fertilization were observed in a series of sperm dilution tested. These laboratory experiments suggest that sperm dilution and its limited longevity can play an important role in limiting the fertilization of sea urchin eggs in the field during natural spawnings. It follows, therefore, that sea urchin (E. mathaei) are under considerable selective pressures to spawn synchronously in order to generate high sperm concentrations and higher sperm-egg encounters in the water column to maximize the probability of successful fertilization.","PeriodicalId":432348,"journal":{"name":"Journal of The Japanese Coral Reef Society","volume":"35 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2001-12-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116668699","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The spatial distribution and morphologies of massive Porites colonies were investigated over a large area (1100m×200m) in the sandy moat of Miyara fringing reef, Ishigaki Island, Japan. Massive Porites (diameter>50cm) showed a preferential distribution for deeper depths (i. e., 2 to 3m). This distribution pattern suggested that massive Porites colonies were transported to deeper more stable habitats, as “mobile colonies”. Twenty-three percent of the colonies were mushroom shaped, with narrow stems attached to the substratum. Significant portions of mushroom shaped colonies (69%) were dislodged and 66% of them were tilted toward the dominant direction of water flow. The mushroom morphologies appear related to the high mobility of sandy sediments around the colonies, which interferes with ordinary growth of the colony base. Mobile colonies seems important for maintaining local coral populations in sandy habitats, which are often unsuitable habitats for larval settlement. In this case, physical environmental factors, such as water movement and micro-geomorphology, influence the distribution and population structure of coral communities in the sandy shallow habitats.
{"title":"The distribution of massive Porites in the moat of Miyara fringing reef, Ishigaki Island, Japan","authors":"T. Satoh, N. Hori, A. Suzuki","doi":"10.3755/JCRS.2000.43","DOIUrl":"https://doi.org/10.3755/JCRS.2000.43","url":null,"abstract":"The spatial distribution and morphologies of massive Porites colonies were investigated over a large area (1100m×200m) in the sandy moat of Miyara fringing reef, Ishigaki Island, Japan. Massive Porites (diameter>50cm) showed a preferential distribution for deeper depths (i. e., 2 to 3m). This distribution pattern suggested that massive Porites colonies were transported to deeper more stable habitats, as “mobile colonies”. Twenty-three percent of the colonies were mushroom shaped, with narrow stems attached to the substratum. Significant portions of mushroom shaped colonies (69%) were dislodged and 66% of them were tilted toward the dominant direction of water flow. The mushroom morphologies appear related to the high mobility of sandy sediments around the colonies, which interferes with ordinary growth of the colony base. Mobile colonies seems important for maintaining local coral populations in sandy habitats, which are often unsuitable habitats for larval settlement. In this case, physical environmental factors, such as water movement and micro-geomorphology, influence the distribution and population structure of coral communities in the sandy shallow habitats.","PeriodicalId":432348,"journal":{"name":"Journal of The Japanese Coral Reef Society","volume":"96 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2000-12-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115684735","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Six species of compound ascidians found in a Fijian seagrass bed dominated by Syringodium isoetifolium were divided into two groups, each occupying somewhat different microhabitats provided by the seagrass. Didemnum molle and Lissoclinum bistratum, both with algal symbiont Prochloron sp., were abundant in high light microhabitats. D. molle was mostly attach to seagrass blades (maximum colony density: 980m-2), while L. bistratum occurred both on seagrass and sediment surfaces in places with sparse seagrass cover (maximum colony density: 11, 500m-2). Trididemnum clinides also had the symbiont Prochloron sp., but it mostly occupied dark microhabitats such as the sheaths of the seagrass. The other 3 species, Didemnum cuculiferum, D. sp. cf. albopunctatum and Trididemnum discrepans, lacked algal symbionts and were rare, all occupying dark places such as seagrass sheaths in areas with dense seagrass cover. Sympatric ascidians, thus, co-exist in seagrass beds and show a different microhabitat use. Ascidians were not distributed evenly over the area of the seagrass bed, but were concentrated in an area between 30 and 84m from the shore, independent of the distribution of seagrass biomass. In dense seagrass patches, light intensities varied greatly between the top and the basal part of the seagrass, and persistence and stability of seagrass as an attachment substrate were also different between leaf blades and sheaths. Populations of D. molle on the seagrasses included many smaller colonies. There were no colonies as large as those in the population on the more stable nearby rock substrates. The small size of the seagrass blades (1.5mm in diameter), their short lifetime (1.5mo) and their lower persistence and stability as an attachment substrate may explain the small size of the colonies on the seagrass.
{"title":"Abundance, population structure and microhabitat use of compound ascidians in a Fijian seagrass bed, with special reference to Didemnum molle","authors":"M. Nishihira, T. Suzuki","doi":"10.3755/JCRS.2000.29","DOIUrl":"https://doi.org/10.3755/JCRS.2000.29","url":null,"abstract":"Six species of compound ascidians found in a Fijian seagrass bed dominated by Syringodium isoetifolium were divided into two groups, each occupying somewhat different microhabitats provided by the seagrass. Didemnum molle and Lissoclinum bistratum, both with algal symbiont Prochloron sp., were abundant in high light microhabitats. D. molle was mostly attach to seagrass blades (maximum colony density: 980m-2), while L. bistratum occurred both on seagrass and sediment surfaces in places with sparse seagrass cover (maximum colony density: 11, 500m-2). Trididemnum clinides also had the symbiont Prochloron sp., but it mostly occupied dark microhabitats such as the sheaths of the seagrass. The other 3 species, Didemnum cuculiferum, D. sp. cf. albopunctatum and Trididemnum discrepans, lacked algal symbionts and were rare, all occupying dark places such as seagrass sheaths in areas with dense seagrass cover. Sympatric ascidians, thus, co-exist in seagrass beds and show a different microhabitat use. Ascidians were not distributed evenly over the area of the seagrass bed, but were concentrated in an area between 30 and 84m from the shore, independent of the distribution of seagrass biomass. In dense seagrass patches, light intensities varied greatly between the top and the basal part of the seagrass, and persistence and stability of seagrass as an attachment substrate were also different between leaf blades and sheaths. Populations of D. molle on the seagrasses included many smaller colonies. There were no colonies as large as those in the population on the more stable nearby rock substrates. The small size of the seagrass blades (1.5mm in diameter), their short lifetime (1.5mo) and their lower persistence and stability as an attachment substrate may explain the small size of the colonies on the seagrass.","PeriodicalId":432348,"journal":{"name":"Journal of The Japanese Coral Reef Society","volume":"54 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2000-12-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124711286","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The thermal environment of reef-building corals is critical to their distribution and survival. Recent evidence has revealed that the mean global temperature has increased by 1 degree Celsius over the past century. Examination of tropical sea temperatures reveal that they have also increased by almost 1°C over the past 100 years and are currently increasing at the rate of approximately 1-2°C per century. Japanese waters are no exception. Waters off Okinawa have increased by 1.4°C since 1930 and are currently increasing at the rate of 2.3°C per century (95% confidence interval, 1.4-3.1°C). Coral bleaching occurs when the thermal tolerance of corals and their zooxanthellae are exceeded, probably due to an increased sensitivity of the zooxanthellae to chronic photoinhibition. The consequences of bleaching can be devastating, with corals dying in vast numbers and such aspects as coral reproduction being severely curtailed. In 1998, the world's coral reefs experienced the worst bleaching on record. Japanese reefs were severely effected, with bleaching coinciding with a massive temperature anomaly in July-August 1998. Vast numbers of corals died. The intention of this paper is collect what we know about coral bleaching from biochemical, physiological and ecological perspectives and to discuss to how reefs (especially around Okinawa) might change in the next century. A single important issue surfaces in these deliberations. If temperatures continue to increase, then corals will experience greater incidences of bleaching and mortality unless they can acclimate physiologically or adapt genetically. The conclusions that stem from this issue are of great concern. Firstly, available evidence suggests that corals are not acclimating physiologically to any really extent to the sporadic and seasonal changes in sea temperature. Secondly, the rate of change in sea temperature arguably exceeds the capacity of coral populations to genetically adapt fast enough. The third conclusion is the most worrying. If corals are not changing fast enough, then coral reefs will experience more frequent and more intense bleaching. Given the outcome for many coral reefs across the planet during the 1998 episodes of bleaching, this has to be of great concern to coral reef users and managers everywhere.
{"title":"Global climate change and the thermal tolerance of corals","authors":"O. Hoegh‐Guldberg","doi":"10.3755/JCRS.2000.1","DOIUrl":"https://doi.org/10.3755/JCRS.2000.1","url":null,"abstract":"The thermal environment of reef-building corals is critical to their distribution and survival. Recent evidence has revealed that the mean global temperature has increased by 1 degree Celsius over the past century. Examination of tropical sea temperatures reveal that they have also increased by almost 1°C over the past 100 years and are currently increasing at the rate of approximately 1-2°C per century. Japanese waters are no exception. Waters off Okinawa have increased by 1.4°C since 1930 and are currently increasing at the rate of 2.3°C per century (95% confidence interval, 1.4-3.1°C). Coral bleaching occurs when the thermal tolerance of corals and their zooxanthellae are exceeded, probably due to an increased sensitivity of the zooxanthellae to chronic photoinhibition. The consequences of bleaching can be devastating, with corals dying in vast numbers and such aspects as coral reproduction being severely curtailed. In 1998, the world's coral reefs experienced the worst bleaching on record. Japanese reefs were severely effected, with bleaching coinciding with a massive temperature anomaly in July-August 1998. Vast numbers of corals died. The intention of this paper is collect what we know about coral bleaching from biochemical, physiological and ecological perspectives and to discuss to how reefs (especially around Okinawa) might change in the next century. A single important issue surfaces in these deliberations. If temperatures continue to increase, then corals will experience greater incidences of bleaching and mortality unless they can acclimate physiologically or adapt genetically. The conclusions that stem from this issue are of great concern. Firstly, available evidence suggests that corals are not acclimating physiologically to any really extent to the sporadic and seasonal changes in sea temperature. Secondly, the rate of change in sea temperature arguably exceeds the capacity of coral populations to genetically adapt fast enough. The third conclusion is the most worrying. If corals are not changing fast enough, then coral reefs will experience more frequent and more intense bleaching. Given the outcome for many coral reefs across the planet during the 1998 episodes of bleaching, this has to be of great concern to coral reef users and managers everywhere.","PeriodicalId":432348,"journal":{"name":"Journal of The Japanese Coral Reef Society","volume":"92 1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2000-12-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130926643","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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