大亚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 DAYA BAY,THE SOUTH CHINA SEA

  • 摘要: 用TFO采泥器于2001年8月采集了大亚湾大鹏澳海域6个采样点8-18cm柱状沉积物样品,分层研究了甲藻孢囊在该海域表层沉积物中的垂直分布.在35个沉积物样品中共分析鉴定出甲藻孢囊48种,其中自养型20种,异养型28种,优势种类为锥状斯氏藻.每个样品中所分析鉴定的孢囊种类数为12-29种,孢囊的香农-威弗种类多样性指数(Shannon-Weaver Diversity Index,H')为0.61-4.13,并且在2-4cm层次处,随深度的增加,两者均有一个明显上升趋势.除鱼类养殖区的上表层较高外,孢囊丰度大多为1000-2000 cysts/g D Wt,最高为2.38×104 cysts/g D Wt.亚历山大藻孢囊分布广泛且密度较高,最高丰度为503 cysts/g D Wt,同时表层沉积物中高密度的亚历山大藻孢囊为该藻赤潮的发生提供了丰富的种源,而且也是该海域贝类体内冬季PSP毒素积累及高含量的重要原因.

     

    Abstract: Six sediment cores from length of 8 to 18cm were collected from DapengAo area,Daya Bay,the South China Sea,by TFO core sampler in Aug. 2001 to investigate the vertical distribution of dinoflagellate resting cysts. 48 different cyst morphotypes representing 20 genera and 6 groups were identified from 35 sediment samples in this study. There were 20 autotrophic species and 28 heterotrophic ones. Cyst species richness in each sample varied from 12 to 29,while the values of Shannon-Weaver’s Diversity Index(H′)were between 0.61 and 4.13. There were an obvious increase of species richness and H’values in the depth of 2—4cm. Cyst concentrations varied from 154 to 2.38×104 cysts/g D Wt,and were between 1000 and 2000 cysts/g D Wt in most samples,while the highest concentration was obtained at the depth of 2—4cm in fish raised area of St.1.Scrippsiella trochoidea was the most common and abundant cyst type. Meanwhile,the abrupt increase of cysts of S. trochoidea in the depth of 2—4cm layer of sediment reflected the bloom of this species in nearby sea areas in 2000. The results from cyst assemblages showed some trend of changes in water quality in this area to some extent,and indicated the typical type of pollution caused by cultural eutrophication,which began in the late 1990s. Cysts of Alexandrium mainly those of A. catenella and A. tamarense complex occurred frequently and abundantly in this area,with the highest concentration and relative frequency of 503cysts/g D Wt and 12.0%respectively. Thus,high concentrations of Alexandrium cysts provided rich“seed bed”for Alexandrium blooms and an important resource of PSP toxin especially in winter.

     

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