open access

https://doi.org/10.14943/bull.fish.69.1.37

https://hdl.handle.net/2115/75197

Zooplankton Size Structure in the Summer Western North Pacific Ocean: Analysis by Optical Plankton Counter

日本語

Normalized biomass size spectra (NBSS)

2019-08-07

北海道大学大学院水産科学研究院

Bulletin of Fisheries Sciences, Hokkaido University

69(1)

37-45

To evaluate latitudinal and east-west changes in zooplankton abundance, biomass and size spectra, Optical Plankton Counter (OPC) measurements were made on zooplankton samples collected by vertical hauls of NORPAC net from 0-150 m depth at 35˚-46˚N along three north-south transects (144˚, 155˚, and 175˚30’E) in the western North Pacific during July-August of 2008 and 2009. Zooplankton abundance and biomass ranged at 4612-241,782 ind. m-2 and 0.05-23.09 g DW m-2, respectively. Zooplankton abundance and biomass were dominated by small-size class (0-1 mm equivalent spherical diameter [ESD]) in the subtropical region, while dominated by large-size class (1-2 and 2-3 mm ESD) in the transitional domain which caused by the dominance of large-sized copepods: Neocalanus spp. and Eucalanus bungii there. Inter-annual changes were observed for the 155˚E line: dominated by large size class (>5 mm ESD) in 2008 which caused by the dominance of Salpida. For size structure of zooplankton, analyses on normalized biomass size spectra (NBSS) were made. East-west differences were detected for the slope of NBSS. Thus, the slopes of NBSS were moderate for eastern lines (175˚30’E). This east-west gradient in NBSS slope may be related to the east-west gradient in primary productivity which related to east-west differences in the magnitude of iron supply from dust. Overall, NBSS slope in the western North Pacific was characterized by moderate and highly variable. It would be related to pulse-like input of nutrient (=sporadic peak of primary productivity) and dominance of large- gelatinous zooplankton. These two factors are considered to be a special characteristic of the plankton community in summer of the western North Pacific.

紀要論文

Version of Record

1346-1842

AA11547977