Structure and species diversity of the zooplankton community of the Inland Sea of Japan

Seasonal fluctuations in composition and abundance of zooplankton of the Inland Sea of Japan were investigated in 1979–1980. Some of the areas in the environment were found to be eutrophic and sharp temperature variations occurred with seasons. In this scenario, zooplankton populations peaked in autumn. Copepods were the dominant component and six species of this group formed about 88% of the total zooplankton counts. Species groups are categorized based on distributional characteristics. Zooplankton composition was more or less homogeneous in each season within the area studied and a few oceanic species which occurred had only limited influence on community structure. Species diversity was low and competition among species was weak. The results indicated a poor quality biotope probably resulting from a deterioration of water quality and an environment which favours r-selection.