엘니뇨/라니냐가 북서태평양 아열대 난수역과 북부동중국해의 중형동물플랑크톤 생체량에 미치는 영향

Abstract

Mesozooplankton biomass including total biomass and size-fractionated biomass and the abundance of major taxonomic groups of copepods were studied in the Northwestern Subtropical Pacific Warm Pool (NSPWP) and the Northern East China Sea (NECS) from 2006 to 2014. Mesozooplankton biomass ranged from 0.69 to 3.08 mgC/m³ (mean 1.12 mgC/m³) in the NSPWP and from 10.60 to 69.10 mgC/m³ (mean 30.33 mgC/m³) in the NECS with higher values in spring than fall. Percent composition in the biomass of each size group of mesozooplankton varied interannually both in the NSPWP and in the NECS. The smallest size group (0.2~0.5 mm) contributed the least to total biomass in both regions, but significantly higher in the NSPWP than in the NECS. The percent composition in abundance of copepod taxonomic groups (i.e. Calanoida, Cyclopoida, and Poecilostomatoida) also fluctuated interannually. Mean composition of calanoid copepods was higher in the NECS than in the NSPWP, but the opposite pattern was observed for poecilostomatoid copepods. Mesozooplankton biomass both in the NSPWP and in the NECS was negatively correlated with Oceanic Nino Index (ONI), indicating declines in biomass during El Nino periods and vice versa during Na Nina period. The effect of El Nino on variation of mesozooplankton biomass was more prominent in the NSPWP than in the NECS. These results suggest that mesozooplankton biomass both in the NSPWP and in the NECS responded to El Nino events, although the biological process that explain the reduced mesozooplankton biomass might be different in both regions.