Annual variations of vertical distribution of copepods 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 2006 to 2007 to understand the relationship between the annual pattern of thermal stratification and variation of copepod composition. Environmental factors such as temperature, salinity and chlorophyll a, which strongly influence the proliferation and diversity of mesozooplankton were also investigated. The concentration of chlorophyll a ranged between 0.01 and 2.14 g/L. Higher concentrations of chlorophyll a were detected in the upper part of the thermocline during the thermal stratification between June and November.The population of copepods was the largest among mesozooplankton groups. There were 33 genera and 72 species of copepods. The proportion of copepods among mesozooplankton groups was from 11.0% to 96.8% during the study. Paracalanus aculeatus, P. crassirostris, P. parvus, Temora discaudata, Oithona similis and Oncaea spp. were dominant copepods. In 2006, P. parvus, which strongly influenced mesozooplankton composition, dominated 88.1% of mesozooplankton at the upper part of water column in late October. P. crassirostris dominated in late August and late September. O. similis was a dominant species in the middle and bottom parts of water column in early November. In 2007, P. parvus mostly dominated during the mixed period of water column, while dominant species were diverse during the thermal stratification. Neritic calanoid copepods were dominant from early August but warm water calanoid copepods were dominant from August or September to December.This study will discuss the influences of Kuroshio Warm Current and thermocline on copepod community structure. Especially indicator species for warm current will be studied