Journal cover Journal topic
Biogeosciences An interactive open-access journal of the European Geosciences Union
Journal topic
Volume 13, issue 15
Biogeosciences, 13, 4555–4567, 2016
https://doi.org/10.5194/bg-13-4555-2016
© Author(s) 2016. This work is distributed under
the Creative Commons Attribution 3.0 License.

Special issue: Catastrophic reduction of sea ice in the Arctic Ocean...

Biogeosciences, 13, 4555–4567, 2016
https://doi.org/10.5194/bg-13-4555-2016
© Author(s) 2016. This work is distributed under
the Creative Commons Attribution 3.0 License.

Research article 12 Aug 2016

Research article | 12 Aug 2016

Distribution of Arctic and Pacific copepods and their habitat in the northern Bering and Chukchi seas

Hiroko Sasaki1,2, Kohei Matsuno1,2, Amane Fujiwara3, Misaki Onuka4, Atsushi Yamaguchi2, Hiromichi Ueno2, Yutaka Watanuki2, and Takashi Kikuchi3 Hiroko Sasaki et al.
  • 1Arctic Environment Research Center, National Institute of Polar Research, 10-3 Midori-cho, Tachikawa, Tokyo 190-8518, Japan
  • 2Graduate School of Fisheries Sciences, Hokkaido University, 3-1-1 Minato-cho, Hakodate, Hokkaido 041-8611, Japan
  • 3Japan Agency for Marine-Earth Science and Technology, 2-15 Natsushima-cho, Yokosuka, Kanagawa 237-0061, Japan
  • 4Graduate School of Environmental Science, Hokkaido University, N10W5, Sapporo, Hokkaido 060-0810, Japan

Abstract. The advection of warm Pacific water and the reduction in sea ice in the western Arctic Ocean may influence the abundance and distribution of copepods, a key component of food webs. To quantify the factors affecting the abundance of copepods in the northern Bering and Chukchi seas, we constructed habitat models explaining the spatial patterns of large and small Arctic and Pacific copepods separately. Copepods were sampled using NORPAC (North Pacific Standard) nets. The structures of water masses indexed by principle component analysis scores, satellite-derived timing of sea ice retreat, bottom depth and chlorophyll a concentration were integrated into generalized additive models as explanatory variables. The adequate models for all copepods exhibited clear continuous relationships between the abundance of copepods and the indexed water masses. Large Arctic copepods were abundant at stations where the bottom layer was saline; however they were scarce at stations where warm fresh water formed the upper layer. Small Arctic copepods were abundant at stations where the upper layer was warm and saline and the bottom layer was cold and highly saline. In contrast, Pacific copepods were abundant at stations where the Pacific-origin water mass was predominant (i.e. a warm, saline upper layer and saline and a highly saline bottom layer). All copepod groups showed a positive relationship with early sea ice retreat. Early sea ice retreat has been reported to initiate spring blooms in open water, allowing copepods to utilize more food while maintaining their high activity in warm water without sea ice and cold water. This finding indicates that early sea ice retreat has positive effects on the abundance of all copepod groups in the northern Bering and Chukchi seas, suggesting a change from a pelagic–benthic-type ecosystem to a pelagic–pelagic type.

Publications Copernicus
Download
Short summary
We constructed the habitat models explaining the spatial patterns of the large and small Arctic copepods and the Pacific copepods of the northern Bering Sea and Chukchi Sea. The adequate models show the importance of water masses and sea ice retreat timing. This finding also indicates that earlier sea ice retreat has positive effects on the abundance of all copepod groups in the northern Bering and Chukchi seas, suggesting a change from a pelagic–benthic-type ecosystem to a pelagic–pelagic type.
We constructed the habitat models explaining the spatial patterns of the large and small Arctic...
Citation