Sun, X. (1993). 海南岛鹿回头珊瑚礁区全新世有孔虫 - Holocene foraminifera from coral reefs of Luhuitou, Hainan island. 古生物学报 - Acta Palaeontologica Sinica. 1993(6): 673-684.

387102

Sun, X.

1993

1993(6): 673-684

Publication

The samples were collected from Luhuitou Peninsula located at the southernmost end of Hainan Island, consisting of 90 species in 40 genera, including 3 new species, Textularia sanyaensis, T.longiflata and Triloculina delicata, and 4 undeterminable species, all of which are similar to those of the Xisha Islands. It is very interesting that foraminifera in Xiaodonghai Bay differ significantly from those in Sanya Bay. 1. The number of foraminifera in one gram of dry sample is 70 in Xiaodonghai Bay, but only 26 in Sanya Bay. 2. Larger foraminifera are abundant in Xiaodonghai Bay, Such as Amphistegina madagascariensis d'Orbigny, A. radiata (Fichtel et Moll), alcarina hainanensis Li, C. spengleri (Gmelin) and Operculina ammonoides (Gronovius), but rare in Sanya Bay except Calcarina hainanensis Li. 3. Calcarina spengleri (Gmelin) and Elphidium craticulatum (Fichtel et Moll) are common in Xiaodonghai Bay, but have not been found in Sanya Bay. 4. In Xiaodonghai Bay, the porcellaneous smaller foraminifera are dominated by Quinqueloculina spp. which are relatively big, with thick test wall and well-developed ornamentation, while in Sanya Bay, they are dominated by Triloculina spp. which are small, with thin test wall and poor ornamentation. Since Xiaodonghai Bay and Sanya Bay are close in neighbourhood, how can such differences be explained? Firstly, Luhuitou is under the influence of tropical monsoon which is dominated by northeast wind in winter and south wind in summer. Xiaodonghai Bay faces the monsoon, and thus has become a high energy habitat with well agitated water and abundant food, while Sanya Bay is on the lee side. Secondly, the salinity of Sanya Bay is lower, due to the influence of brackish water from Sanya Lagoon and from alongshore current of Beibu Gulf. These two main factors result in the foraminiferal differences. The foraminifera in Xaidonghai Bay are doiminated by the five larger species with strong tests to survive in the high energy habitat. From abrasion test it has been found that Calcarina spengleri (Gmelin) and Amphistegina madagascariensis d'Orbigny are the two strongest species; the former has large nodules and spines on the surface, and the latter has thick walls and a large number of tightly connected small chambers. It has also been found that Calcarina hainanensis Li has stronger tests in Xiaodonghai Bay than in Sanya Bay. Test strength appears to be closely associated with external physical environment. Generally, foraminiferal tests are stronger in high energy habitat than in low one.

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