Impact of sea-ice reduction on the plankton community in the Pacific sector of the Arctic Ocean

Abstract

This article describes the outline of research result on the effects of sea-ice reduction on the plankton community in the Pacific sector of the Arctic Ocean obtained by the author and his colleagues. In the Pacific sector, abundances of microprotists and zooplankton community were higher in the shelf (Chukchi Sea) than those in the basin due to the intrusion of high-nutrient Pacific Water into the shelf. In the Chukchi Sea, zooplankton abundance and biomass were higher in 2007/08 (when sea-ice melted) than those of 1991/92 (when sea-ice remained), meaning that sea-ice reduction could increase the productivity of the zooplankton community. With this change, the northward migration of Arctic species was also observed, indicating that Pacific species could be more dominant in the Arctic Ocean with sea-ice reduction. In the basin, seasonal changes in the zooplankton community were governed by sea-ice concentration, phytoplankton bloom and life cycle (vertical migration) for each species. This finding suggests that sea-ice reduction may affect seasonal changes in the basin zooplankton community of the Arctic Ocean. From shipboard experiments, the reproduction success of Pacific species and the hatchability of eggs were also revealed for the Pacific sector of the Arctic Ocean.