Taxonomy of the nonarticulated coralline algae in the coral reef environment

本文根据琉球群岛冲绳岛附近119个珊瑚礁至岛礁陆架（水深50 ~ 200 m）的取样资料，研究了红柱石的分布、丰度和组成。在70个浅于135米的地点发现了蔷薇辉石。最大时，红柱石的覆盖率约为75%，每平方米约有300块直径大于3厘米的红柱石。这些红柱石呈球状、椭圆形或少数盘状，平均直径50- 10 cm，主要由薄壳状无节珊瑚藻和包壳有孔虫Acervulininhaerens组成，两者形成不同程度的同心或不规则内部结构。生物侵蚀频繁，使红柱石多孔。已鉴定的无关节珊瑚藻有27种，分属于海绵藻属、石孔藻属、石叶藻属、中叶藻属和石羊膜属。在这些属中，石壳藻属（Lithothamnium）是最具优势和多样性的属，共有11种。无节珊瑚藻在深度小于120米的红柱石表面上大量生长，而A.inhaerens在深度超过120米时占主导地位。在石垣岛浅部珊瑚礁环境中，大量的红柱石的存在反映了有机碳和无机碳的现场临界产量。该物种的净有机生产/无机生产比为1/0.9。

The distribution, abundance, and composition of rhodoliths are investigated on the basis of 119 grab samples taken around Okinawa-jima, Ryukyu Islands, covering the deep fore reef to island shelf, which ranges in depths from 50 to 200m. The rhodoliths are found from 70 sites at depths shallower than 135m. Coverage of the rhodoliths is about 75% at its maximum, where about 300 rhodoliths larger than 3cm in diameter occur in 1m^2. These rhodoliths are spheroidal, ellipsoidal or rarely disk-like in shape, 50-10cm in mean diameter, and composed of mainly of thin crustose forms of nonarticulated coralline algae and the encrusting foraminifer Acervulina inhaerens, both of which form more or less concentric or irregular internal structure. Bioerosion is frequent, making the rhodoliths porous. Twenty seven species of the nonarticulated coralline algae have been identified, coming under the genera Spongites, Lithoporella, Lithophyllum, Mesophyllum and Lithothamnion. of these genera, Lithothamnion is the most dominant and diverse, reaching 11 species. The nonarticulated coralline algae grow in common to abundance on the surface of the rhodoliths at depths less than 120m, while A.inhaerens predominates at depths exceeding 120m. The presence of a large quantity of rhodoliths on the deep forereef to island shelf mirrors the on-the-spot production of critical amounts of organic and inorganic carbon.Carbon production of Lithophyllum pallescens, which is luxuriating in the shallow coral reef environment of Ishigaki Island, is mesurerd by alkalinity anomary method. The net organic production / inorganic production ratio of the species is 1/0.9.