Studies on non-dominancy of large diatoms and the mechanism for maintaining their populations in the pelagic ocean

在过去3年的研究中，在中西太平洋50 ° N至65 ° S的大范围内进行了实地观测和取样。在中太平洋，在3 ~ 5年中，在同一季节进行多次重复观测，并在同一区域进行不同季节的观测。细胞或菌落长度> 100 μ m的大型硅藻因其易于在自然界中识别而受到特别关注。在整个研究区，大型硅藻的数量在几种到几十种之间，显示了大型硅藻的广泛分布。研究区外无分布种，但有些种分布在1000 km以上，有些种分布在100 km以内。其分布可分为6-8种类型。各硅藻种的丰度在高纬度地区均达到百分之几，而在其他地区均&lt;10^<-4>。由于各硅藻种生物量较大，生物量优势度较大，在高纬度地区达50%以上，而在其他地区均小于10%<-2>。从本研究中，大型硅藻可能发生在非优势的海洋区域和季节确定。这给了我们研究海洋物种非恶魔性的希望。

During the past 3 years of research, field observations and samplings were carried out covering a large area from 50ﾟN to 65ﾟS in the central and western Pacific Ocean. In the central Pacific, repeated observations in a same period of season were made several times during 3 to 5 years as well as making observations in different seasons in the same area. Large diatom species of >100um in length of cell or colony were particularly concerned because of their easy recognition from natural community. Several to a few 10 species of large diatoms were always found in the entire study area, which demonstrated a wide generous distribution of the large diatoms. No species was distributed throuout the study area but some species occurred in the area of over few 1000km and some others were within a few 100km. The distribution was grouped in 6-8 types. Numerical abundances of each diatom species reached a few % in high latitudes but they were <10^<-4> in the rest of areas. Due to a large biomass of each diatom species, dominancy of biomass became fairly large reaching over 50% at high latitudes, but they were <10^<-2> in the rest of areas. From the present study, ocean areas and seasons where the large diatoms possibly occurred in non-dominance were identified. This has given us a promise to study non-demonancy of species in the ocean.