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Vol. 54, 2015
Spatial
and temporal changes in zooplankton abundance, biovolume, and size
spectra in the neighboring waters of Japan: analyses using an optical
plankton counter
Kaede Sato1, Kohei Matsuno2,
Daichi Arima1, Yoshiyuki Abe1, and Atsushi Yamaguchi1,*
1Laboratory
of Marine Biology, Graduate School of Fisheries Science, Hokkaido
University, 3-1-1 Minatomachi, Hakodate, Hokkaido 041-8611, Japan
2Arctic Environmental Research Center, National Institute of Polar Research, 10-3 Midori-cho, Tachikawa, Tokyo 190-8518, Japan
Abstract
Background: An
optical plankton counter (OPC) was used to examine spatial and temporal
changes in the zooplankton size spectra in the neighboring waters of
Japan from May to August 2011.
Results: Based
on the zooplankton biovolume of equivalent spherical diameter (ESD) in
45 bins for every 0.1 mm between 0.5 and 5.0 mm, a Bray-Curtis cluster
analysis classified the zooplankton communities into six groups. The
geographical distribution of each group varied from each of the others.
Groups with a dominance of 4 to 5 mm ESD were observed in northern
marginal seas (northern Japan Sea and Okhotsk Sea), while the least
biovolume with a dominance of a small-size class (0.5 to 1 mm) was
observed for the Kuroshio extension. Temporal changes were observed
along the 155° E line, i.e., a high biovolume group dominated by 2 to 3
mm ESD during May shifted to other size spectra groups during July to
August. These temporal changes were caused by the seasonal vertical
descent of dominant large Neocalanus copepods during July to August. As
a specific characteristic of the normalized biomasssize spectra (NBSS), the slope of NBSS was moderate (−0.90) for the Neocalanus
dominant spring group but was at −1.11 to −1.24 for the other groups.
Theoretically, the slope of the NBSS of the stable marine ecosystem is
known to settle at approximately −1.
Conclusions: Based
on the analysis by OPC, zooplankton size spectra in the neighboring
waters of Japan were separated into six groups. Most groups had −1.11
to −1.24 NBSS slopes, which were slightly higher than the theoretical
value (−1). However, one group had a moderate slope of NBSS (−0.90)
caused by the dominance of large Neocalanus copepods.
Key words: NBSS; Neocalanus; OPC; Zooplankton .
*Correspondence: E-mail: a-yama@fish.hokudai.ac.jp
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