舟山港4艘商船压舱箱沉积物中甲藻孢囊种群结构的分析

Analysis of the population structure of dinoflagellate cysts in the sediment of ballast tank of four cargo boats at Zhoushan Port

为了解商船压舱箱沉积物在海洋水生生物入侵过程中扮演的潜在媒介作用,本文利用光学显微镜观察法,研究了停泊于我国舟山港4艘商船压舱箱沉积物中甲藻孢囊的种类组成、孢囊密度、香农-威纳指数(H′)和PSP原因种,并对甲藻孢囊种群结构进行了相关性分析。结果表明,鉴定出的甲藻孢囊隶属于5大类,共24种,4份样品中甲藻孢囊的种群结构各有差异,但均检测出能产生麻痹性贝毒(Paralytic Shellfish Poisons,PSP)的甲藻孢囊,如亚历山大藻Alexandriumspp.和链状裸甲藻Gymnodium catenatum。在4艘商船的压舱箱沉积物中均检测出有硅藻分布,其中在富成轮压舱箱沉积物中还检测出3种未知种孢囊。通过相关性分析可知,甲藻孢囊H′值与PSP甲藻孢囊密度占总甲藻孢囊密度的比率呈负相关。甲藻可以通过商船压舱箱沉积物为传播媒介,以孢囊形式来扩大其生物地理分布,提高甲藻物种多样性可有助于降低PSP甲藻的破坏风险。因此,有效处理船只压舱箱沉积物、积极保护当地海洋生物物种多样性,对于降低外来甲藻物种(特别是一些有毒有害种)的赤潮风险和保持当地海洋生态系统的平衡,具有十分重要的意义。

Ballast water of the merchant vessel plays an important role in the invasion of alien marine species which may damage the local marine ecosystem.However,the potential role of the ballast tank sediment in the transmission of the alien species is always underestimated.Using optical microscopic viewing method,the species composition,cyst density,Shannon-Weiner index（H′）,Paralytic Shellfish Poisons（PSP） causative species and their relationships of the dinoflagellate cysts from the sediment of four cargo boats at Zhoushan Port were studied,and 24 types of dinoflagellate cysts of 5 groups were identified including some toxic species such as Alexandrium spp.and Gymnodium catenatum which could produce PSP.Three dinoflagellate cysts of unknown species were also found in the sediment from FUCHENG vessel.Although the population structure of the dinofflagellate cysts in the samples from four vessels were different,some PSP dinoflagellate cysts and diatom cells were all found.Correlation analysis shows that H′ of dinoflagellate cysts was negatively related to the percentage of PSP dinoflagellate cysts in the total dinoflagellate cysts,which indicates that dinoflagellates could expand their biogeographical distribution by the cyst in the sediment of ballast tank and an increase of local dinoflagellate biodiversity may lead to a decrease of the risk of PSP dinoflagellates.Therefore,appropriate treatment of the sediment and positive protection of local marine biodiversity are badly needed and urgent.