Evaluation for the role of Noctiluca scintillans on the material circulation in the Coastal Sea

夜光藻广泛分布于世界各大洋，在濑户内海全年都有分布，尤其是春季至夏季。人们认识到，细胞液中高浓度的氨对鱼类有毒，该物种的异常大规模发展可能对沿海鱼类养殖造成严重损害。另一方面，该异养甲藻细胞液中铵态氮、磷酸盐和硅酸盐的含量分别为2470、183和54 pmol ind·L ~（-1），是近岸海域氮磷循环的重要生物之一<-1>。该物种天然细胞的颗粒C：N：P比估计为143：14：1。水体表层的氨氮和磷酸盐浓度与采样点的微囊藻细胞丰度有关。在水体最上层（0-10 cm），微囊藻提供的铵态氮和磷酸盐分别是环境海水的16倍和25倍。然而，斑块内的硅酸盐浓度接近周围的水。以硅藻海链藻为饵料的微囊藻粪球的形态，通过扫描电子显微镜检查。完全由完整的硅藻细胞组成的粪便颗粒。由此可见，藻类细胞以粪膜的形式排出硅，因此在红潮范围内并没有观察到明显高浓度的硅。在水柱的最高部分，由N. nacians释放的营养物质可以随后被生活在可获得光和碳源的海面上的其他自养物种利用。

Noctiluca scintillans are widely distributed throughout whole oceans in the world and are also known to live in the Seto Inland Sea throughout the year, especially from spring to summer. It was recognized that ammonia included in high concentration in cellular fluid was toxic to fish and an extra-ordinary mass development of this species can cause severe damages to coastal fish farming. On the other hand, this heterotrophic dinoflagellate may act as one of the most important organisms contributing to nitrogen and phosphorus cycle in the coastal sea because of its significantly high content of ammonium nitrogen and phosphate.Ammonium nitrogen, phosphate, and silicate concentrations in cell fluid were estimated at 2470,183, and 54 pmol ind^<-1>, respectively. Particulate C : N : P ratio of the natural cells of the species was estimated at 143 : 14 : 1. Ammonium nitrogen and phosphate concentrations at surface layr of the water column seemed to be related to cell abundance of N.scintillans at the sampling location. Patches of N.scintillans provided 16 and 25 times of ammonium nitrogen and phosphate, respectively, in the uppermost layr (0-10 cm depth) of the water column, higher than those which contained in the ambient sea water. Silicate concentration within patches, however, was close to that in surrounding water. Morphological of fecal pellet of N.scintillans fed on the diatom, Thalassiosira sp., was examined by a scanning electron microscope. Fecal pellet composed entirely of intact diatom cells. It could be inferred that cells excrete silica as fecal pellcts and thus no remarkably high silicate concentration within red tide patches was observed. Relcased nutrients by N.scintillans at the uppermost part of the water column could be subsequently utilized by other autotrophic species living at the sea surface where light and carbon sources are available.