Seasonal changes of vertical dustribution of mesozooplankton in the Korea Strait

Abstract

The profile of a fixed site at station M (34.77 N, 129.13 E) in the Korea Strait was studied from March 2006 to February 2007 to understand the relationship between theannual pattern of thermal stratification and the seasonal variation of mesozooplankton composition. Environmental factors such as temperature, salinity and chlorophyll a, which strongly influence the proliferation and diversity of mesozooplankton were also investigated. The population of copepod was the largest among mesozooplankton groups. There were 27 genera and 66 species of copepods. Mesozooplankton was classified into 19 groups to the minimum and 52 groups to the maximum during the study due to the seasonal variation and depth of water column. The number of mesozooplankton groups fluctuated after March 2006 and increased from September. The greater number of mesozooplankton groups was found at the lower part of water column than at the upper part. Copepod dominated mesozooplankton community during the study. The proportion of copepod among mesozooplankton groups was from 24.5% to 96.8% during the study and was smaller in April and May compared to the rest of study period.Dominant copepod species were Paracalanus parvus, P. crassirostris and Oithona similis. This study will discuss the influences of Kuroshio Warm Current and thermocline on mesozooplankton community structure. Especially indicator species for warm current will be studied.