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有“海底公园”之称的珊瑚礁是太平洋的特徵之一,在太平洋中部热带海特别发达,南中国海东沙、西沙、中沙、南沙诸羣岛一百五十九个岛屿全部都是珊瑚岛。珊瑚礁由石灰质的海洋生物所构成。构成珊瑚礁的石灰质海洋生物,有珊瑚蟲、石灰藻(又名珊瑚藻)、藓蟲类、和牡蛎壳的化石等种,其中以珊瑚蟲及石灰藻构成的珊瑚礁最多。造礁珊瑚蟲能分泌一种炭酸钙为构成珊瑚礁的主要成分。珊瑚蟲生长的必要条件有三:一、热带亚热带的海洋,水温须在摄氏二十度以上,二、水深须在五十公尺以内,三、海水须稳静澄清没有淡水混入。所以珊瑚礁多分布在赤道南北各十八度以内的
The coral reef known as the “Submarine Park” is one of the characteristics of the Pacific Ocean. It is particularly developed in the central Pacific Ocean and the tropical seas in the central Pacific Ocean. The 159 islands of Dongsha, Xisha, Zhongsha and Nansha Islands in the South China Sea are all coral islands. Coral reefs consist of calcareous marine life. The calcareous marine organisms that make up coral reefs include corals, algae (also known as coralline algae), aphids, and fossils of oyster shells. Among them, coral reefs and limestone algae constitute the largest coral reefs. Reef-building corals secrete calcium carbonate as the main component of coral reefs. There are three essential conditions for the growth of corals: First, tropical and subtropical oceans, the water temperature must be above 20 degrees Celsius, two, the water depth must be within 50 meters, three, the seawater must be calm and clear without fresh water mixing. Therefore, coral reefs are distributed over eighteen degrees north and south of the equator.