PRESERVATION OF DINOFLAGELLATE CYSTS IN SURFACE SEDIMENTS OF INNER BAYS

对于澄清水环境中的营养物质等变化，硅藻和甲藻等浮游植物群落是非常有用的。在甲藻中，营养细胞群落比包囊群落更有用，尤其是富营养化。不幸的是，所有现代甲藻都不能产生保存在沉积物中的休眠胞囊。因此，当我们使用包囊群落时，我们必须了解保存在沉积物中的甲藻包囊的偏向。遗憾的是，目前对这一主题的研究还很少。在这项研究中，我们采集了长崎县Mie 0-a湾的松谷湾的浮游生物和包囊样本，在那里，甲藻营养细胞的历史记录一直保存了30多年。在松屋湾的2个站点和0-Mura湾的1个站点，用手持的活塞芯采集了3个柱芯沉积物，没有严重的沉积物干扰。测得这些岩心的平均沉积速率分别为0.55 cm/年(Matoya Bay St.1)、0.41 cm/年(Matoya Bay St.2)和0.31 cm/年(0-5)。根据这些沉积速率，沉积物中的记录可能分别追溯到120、125和145年前。松屋湾St1的甲藻孢囊群落至少由18属34种组成，其中包括几个不确定的种。在刚尾藻类群中，以斑纹藻(Linguloddium Machaerophorum)、泡刺棘藻(Spiniferites Bulloideus)、贝氏棘藻(Spiniferites Belerius)和斑纹藻(Brigantedina spp.)为主。(=原球藻Protperiddium spp.)在类胡萝卜素组中含量丰富。共鉴定出浮游生物32属134种。其中，仅有9属17种孢囊型与浮游生物种类相对应。特别是，没有从沉积物中发现前中心藻类和脊椎动物的包囊。这有力地表明，与浮游生物群落相比，来自包囊群落的信息非常有限。

For clarifying a change such as nutrients in aquatic environments, such phytoplankton communities as diatoms and dinoflagellates are very useful. In dinoflagellates the vegetative cell community is more useful than the cyst community, especially the eutrophication. Unfortunately all modern dinoflagellates can not produce a resting cyst which is preserved in sediments. Therefore, when we employ the cyst community, we have to understand a bias of dinoflagellate cyst preserved in sediments. Unfortunately there are only a few study on this subject for the moment.In this study, we collected plankton and cyst samples from Matoya Bay in Mie the 0mura Bay in Nagasaki Prefecture, where historical record of dinoflagellate vegetative cells has been kept throughout over past 30 years. In 2 sites of Matoya Bay and 1 site 0mura Bay, three core sediments were collected with a handy piston core with out serious disturbance of sediments. After measurement of 210Pb, the average sedimentation rates of these cores are estimated as 0.55cm/year (Matoya Bay St.1), 0.41cm/year (Matoya Bay St. 2) and 0.31cm/year (0mura Bay St.5). According to these sedimentation rates, the record in sediments may be back to 120, 125 and 145 years ago respectively.Dinoflagellate cyst community of St.1 in Matoya Bay consists of at least 18 genera and 34 species including several undeterminable species. In gonyaulacoid group, Lingulodinium machaerophorum (= L. polyedrum), Spiniferites bulloideus (= Gonyaulax scrippsae), Spiniferites belerius were dominated and Brigantedinium spp. (= Protoperidinium spp.) were abundant in protoperidinioid group. 32 genera and 134 species of plankton form were identified. Among them, only 9 genera and 17 species in cyst forms were corresponding with plankton species. In particular, no cysts of prorocentlales and dinophysales were recovered from the sediments. This strongly suggests that the information from cyst community is very limited in comparison with plankton community.