柘林湾近代沉积物中甲藻孢囊的垂直分布

Vertical Distribution of Dinoflagellate Resting Cysts in Recent Sediments from Zhelin Bay, the South China Sea

于 2001 年 月在柘林湾 个采样点采集了各约 4 3 20 cm的沉积物柱状样,分层研究了甲藻孢囊的垂直分布。在 个沉积物样品中共分析鉴定出甲藻孢囊47 种,而且还观察到了 种该海域特有的种类。 33 3孢囊组成以原多甲藻等异养型孢囊为主,而有毒的亚历山大藻和链状裸甲藻孢囊也均有分布。每个样品中所分析鉴定的孢囊种类数较少,仅有 ～ 种,平均 种。孢囊丰度也较低,在 ～ 5 16 10 59 1 998 cysts/g D Wt之间,平均 280 cysts/g D Wt。香农-威弗种类多样性指数和孢囊种类数都以位于非养殖区湾外海域的 S3站最高,同时在3 个站位的6～8 cm 层次处,随深度的增加均有较大幅度的上升。研究结果表明,柘林湾的富营养化程度较高,而且湾内海域大于湾外海域,养殖区大于非养殖区,近年有加剧的趋势。

Three sediment cores about 20 cm in length were collected from the Zhelin Bay, the South China Sea by TFO core sampler in April 2001 to investigate the vertical distribution of dinoflagellate resting cysts. 47 different cyst morphotypes representing 21 genera and 6 groups were identified from 33 sediment samples in this study, while three were the endemic new reported types. Cyst species richness in each sample was low, which varied from 5 to 16 with an average of 10. Heterotrophic cysts, mainly those in protoperidinioid, dominated in cyst assemblages. Abundance was low and ranged from 59 to 1998 cysts/g D Wt with an average of 280 cysts/ g D Wt. The values of Shannon-Weaver Diversity Index (H') and the species richness were higher in the offshore area than in the inshore cultural area. An abrupt decrease of the values of H and species richness was observed in the depth of 6～8 cm sediments, which indicated deterioration of water quality. From the results of cyst record in sediment, we suggest that the Zhelin Bay has been heavily enriched especially in the inshore cultural area and the situation has become more severe recently. This is the first report about distribution of dinoflagellate cysts in this area.