On the maintenance mechanisms of scleractinian coral community in a peripheral area.

周边地区石珊瑚群落的维持机制研究.

基本信息

批准号：
02640511
负责人：
NOJIMA Satoshi
金额：
$ 1.22万
依托单位：
Kumamoto University (1992)Kyushu University (1990-1991)
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (C)
财政年份：
1990
资助国家：
日本
起止时间：
1990 至 1992
项目状态：
已结题

项目摘要

In comparison with the coral communities of Sesoko Island of Okinawa (in coral reef area). some features of the coral communities in Amakusa have been made clear.1) In spite of the long coast line, suitable shallow area for coral growth is narrower than that of coral reef area. However in several areas in Amakusa, coverages of corals sometimes reached 75%, and were not so much differed from that of Okinawa. However, total number of eggs spawned in Amakusa was quite fewer than in okinawa. 2) Presumably for this reason, density of larval settlement in Amakusa was quite low, only 1/10000 of Sesoko Is. 3) Effect of grazer such as Echinometra seemed as a distinct mortality factor of young corals. Density of this grazer is lower in Amakusa than Sesoko. Consequently, the discrepancy of both areas decreased relatively and the density of young corals in Sesoko Is. reached only 5 times of that in Amakusa. 4) During the growing season, the growth rate of corals in Sesoko Is. was 1.5 times higher … More than in amakusa. If the 5 times density is continuously maintained, rapid increment of coverage is expected in Sesoko Is. However, such rapid change in coverage have been not reported. This fact shows that some powerful predators such as Acanthaster and other influential mortality factors cause the reduction in the density. However, such influential factors lowering the density were raltively rare in Amakusa. According to the general survey on the distribution of corals by manta-method carried out in 1990, feeding scars and colonies partially died were rare in Amakusa. 5) It reported that most of corals in Amakusa died during the severe cold wave of 1962/63 winter. Diameter of table type corals, such as Acropora soliataryensis, sometimes reaches up to 2 m in Amakusa. If annual growth rate of 9 mm in diameter, measured in the present study, continues for 30 years, the maximum size of table type corals now present agree with the above report. This fact shows that scleractinian corals in Amakusa are growing under good conditions after the cold wave. Size frequency data of A. solitaryensis showed a successive pattern from small to large size. This successive size structure suggests a continuous settlement of young colonies. 6) In Amakusa where there is no powerful predator, effective mortality factors seem to be low temperature in winter, high temperature in summer and wave action during typhoon season. Many borers associated with corals also seems to contribute this reduction of corals during typhoon. Less

与冲绳濑底岛（珊瑚礁区）的珊瑚群落比较，清楚了天草珊瑚群落的一些特征。1）尽管海岸线很长，但适合珊瑚生长的浅水区较窄。然而，天草的一些地区的珊瑚覆盖率有时达到75%，与冲绳的情况相差不大，但天草的产卵总数却比冲绳少得多。 2) 大概由于这个原因，天草的幼虫定居密度相当低，仅为濑底群岛的 1/10000。 3) 食草动物（如 Echinometra）的影响似乎是幼珊瑚的一个明显的死亡因素。天草岛的珊瑚密度低于濑底岛，两者的差异相对较小，濑底群岛的幼珊瑚密度仅达到5。 4) 在生长季节，濑底群岛的珊瑚生长速度是天草群岛的 1.5 倍……如果持续保持 5 倍的密度，濑底群岛的覆盖率预计会迅速增加。然而，这种覆盖范围的快速变化尚未见报道。这一事实表明，一些强大的捕食者，如棘蝽和其他影响死亡的因素导致了密度的降低。根据1990年对珊瑚分布进行的蝠鲼法调查，天草珊瑚很少出现摄食疤痕和珊瑚群部分死亡的现象。5)据报道，天草珊瑚大部分在严寒期间死亡。 1962/63 年冬季，表型珊瑚（例如 Acropora soliataryensis）的年生长速度有时可达 2 m。本研究测量的直径为9毫米，30年来目前存在的桌型珊瑚的最大尺寸与上述报告一致，这一事实表明，寒潮过后，天草石珊瑚在良好的条件下生长。 A. solitaryensis 的尺寸频率数据显示了从小到大尺寸的连续模式，这种连续的尺寸结构表明年轻群体的连续定居。 6) 在没有强大捕食者的天草，有效的死亡因素似乎是低温。冬季、夏季高温和台风季节的波浪作用似乎也导致了台风期间珊瑚的减少。