COMPARISON OF LONG-TERM TRENDS OF ZOOPLANKTON FROM TWO MARINE ECOSYSTEMS ACROSS THE NORTH PACIFIC: NORTHEASTERN ASIAN MARGINAL SEA AND SOUTHERN CALIFORNIA CURRENT SYSTEM

Abstract

Long-term trends of zooplankton biomass and major zooplankton taxa were examined across the North Pacific in the Northeastern Asian Marginal Sea (NeAMS) and the Southern California Current System (SCC) to test for evidence of basin-scale synchrony.Zooplankton biomass showed contrasting long-term patterns in the two regions: an increasing trend (as wet mass) in the NeAMS, but a decreasing trend (as displacement volume) in the SCC.Zooplankton biomass covaried with the Pacific Decadal Oscillation in the NeAMS, but with the North Pacific Gyre Oscillation in the SCC.In the NeAMS, increasing zooplankton biomass was closely associated with increases of all major zooplankton groups (copepods, chaetognaths, euphausiids, and hyperiid amphipods).In the SCC, decreasing zooplankton biomass was caused by declining tunicates and chaetognaths.Seasonal cycles and responses to El Nio also differed between the two regions.In this cross-basin comparison, zooplankton showed differing patterns that reflect region-specific physical and biotic processes rather than synchronous responses to large-scale atmosphere-ocean forcing.