Abstract. In the Chukchi Sea, due to the recent drastic reduction of sea-ice during the summer, an increasing formation of atmospheric turbulence has been reported. However, the importance and effects of atmospheric turbulence on the marine ecosystem are not fully understood in this region. To evaluate the effect of atmospheric turbulence on the marine ecosystem, high-frequent sampling (two to four times per day) on the mesozooplankton community and the gut pigment of dominant copepods were made 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 standing stock of chlorophyll a (chl a) was increased, especially for micro-size (> 10 μm) fractions. Zooplankton abundance ranged 23 610–56 809 ind. m−2 and exhibited no clear changes with SWE. In terms of abundance, calanoid copepods constituted the most dominated taxa (mean: 57%), followed by barnacle larvae (31%). Within the calanoid copepods, small-sized Pseudocalanus spp. (65%) and large-sized Calanus glacialis (30%) dominated. In the population structure of C. glacialis, copepodid stage 5 (C5) dominated, and the mean copepodid stage did not vary with 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, and a significant increase was observed after SWE (2.6 vs. 4.5 ng pigment ind.−1). Assuming C : Chl a ratio, 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 standing stock of micro-size phytoplankton. Compared with the metabolic food requirement, their feeding on phytoplankton accounted for 12.6% of their total food requirement. These facts suggest that C. glacialis could not maintain their population on solely phytoplankton food, and other food sources (i.e., microzooplankton) are important in autumn. As observed for the increase in gut pigment, temporal phytoplankton bloom, which is enhanced by the atmospheric turbulence (SWE) in autumn, may have a positive effect on copepod nutrition. However, because of the relatively long generation length of copepods, a smaller effect was detected for their abundance, population structure, lipid accumulation and gonad maturation within the short-term period (16 days).
Assessing Bioresources and Standing Stock of Zoobenthos (Key Species, High Taxa, Trophic Groups) in the Chukchi Sea
