Articles | Volume 12, issue 13
Biogeosciences, 12, 4005–4015, 2015

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

Biogeosciences, 12, 4005–4015, 2015

Research article 03 Jul 2015

Research article | 03 Jul 2015

Short-term changes in the mesozooplankton community and copepod gut pigment in the Chukchi Sea in autumn: reflections of a strong wind event

K. Matsuno1, A. Yamaguchi2, S. Nishino3, J. Inoue1, and T. Kikuchi3 K. Matsuno et al.
  • 1Arctic Environment Research Center, National Institute of Polar Research, 10-3 Midori-cho, Tachikawa, Tokyo 190-8518, Japan
  • 2Laboratory of Marine Biology, Graduate 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

Abstract. To evaluate the effect of atmospheric turbulence on a marine ecosystem, high-frequency samplings (two to four times per day) of a mesozooplankton community and the gut pigment of dominant copepods were performed at a fixed station in the Chukchi Sea from 10 to 25 September 2013. During the study period, a strong wind event (SWE) was observed on 18 September. After the SWE, the biomass of chlorophyll a (Chl a) increased, especially for micro-size (> 10 μm) fractions. The zooplankton abundance ranged from 23 610 to 56 809 ind. m−2 and exhibited no clear changes as a result of the SWE. In terms of abundance, calanoid copepods constituted the dominant taxa (mean: 57 %), followed by barnacle larvae (31 %). Within the calanoid copepods, small-sized Pseudocalanus spp. (65 %) and large-sized C. glacialis (30 %) dominated. In the population structure of C. glacialis, copepodid stage 5 (C5) dominated, and the mean copepodid stage did not vary with the SWE. The dominance of accumulated lipids in C5 and C6 females with immature gonads indicated that they were preparing for seasonal diapause. The gut pigment of C. glacialis C5 was higher at night and was correlated with ambient Chl a (Chl a, and a significant increase was observed after the SWE (2.6 vs. 4.5 ng pigment ind.−1). The grazing impact by C. glacialis C5 was estimated to be 4.14 mg C m−2 day−1, which corresponded to 0.5−4.6 % of the biomass of the micro-size phytoplankton. Compared with the metabolic food requirement, C. glacialis feeding on phytoplankton accounted for 12.6 % of their total food requirement. These facts suggest that C. glacialis could not maintain their population by feeding solely on phytoplankton and that other food sources (i.e., microzooplankton) must be important in autumn. As observed by the increase in gut pigment, the temporal phytoplankton bloom, which is enhanced by the atmospheric turbulence (SWE) in autumn, may have a positive effect on copepod nutrition.

Short summary
We performed high-frequency samplings of zooplankton community and gut pigment of copepods in the Chukchi Sea. Zooplankton showed no changes with a strong wind event and dominant copepods prepared for diapause. Yet, feeding activity of the copepods increased as a result of temporal phytoplankton bloom, enhanced by the wind event. Because of the long generation length of copepods, a smaller effect was detected for their abundance, population, lipid accumulation and gonad maturation.
Final-revised paper