Interannual and latitudinal changes in zooplankton abundance, biomass and size composition along a central North Pacific transect during summer: analyses with an Optical Plankton Counter

Abstract

2 but the differences between the three oceanic domains were not significant. However, highly significant latitudinal changes were observed in the mean zooplankton biomass, which ranged from 1.44 to 13.2 mg dry mass m 2 with higher values in the Transitional Domain (TR) than in the Subarctic and Subtropical Domains. The high biomass in the TR was caused by the dominance of large-sized zooplankton with equivalent spherical diameters (ESD) of 2-4 mm, regarded to consist mainly of Neocalanus spp. C5. Both the slope and intercept of the Normalized Biomass Size Spectrum also showed significant latitudinal changes with a moderate slope and low intercept in the TR due to the dominance of large zooplankton with 2-4 mm ESD in biomass. In contrast to these large latitudinal changes, only limited interannual variations were observed for zooplankton abundance and biomass in the central North Pacific during the study period.

Spatial and temporal changes in zooplankton abundance, biovolume, and size spectra in the neighboring waters of Japan: analyses using an optical plankton counter

“…Table 3 summarizes regressions between the OPC-derived mass and directly measured mass, ranges of zooplankton abundance, and biovolume from previous studies. The OPCderived masses were 1.05 to 1.18 times the directly measured mass in previous studies (Yokoi et al 2008;Matsuno and Yamaguchi 2010;Fukuda et al 2012). In this study, the zooplankton biovolume estimated by OPC was 0.95 times the directly measured mass (Figure 3).…”

“…In May, group C, which is characterized by a high biovolume and dominance of the 2 to 3 mm ESD size class, dominated; however, this changed to other groups during July to August (Figure 6). The 2 to 3 mm ESD zooplankton in this region corresponded with the C5 stages of large copepods Neocalanus spp., and their importance has been reported in previous OPC studies (Yokoi et al 2008;Matsuno and Yamaguchi 2010;Fukuda et al 2012). Along the 155°E line, group C was dominated by the 2 to 3 mm ESD size class and was characterized by a high biovolume during May and at the northern stations from July to August.…”

“…, respectively (Yokoi et al 2008;Matsuno and Yamaguchi 2010;Fukuda et al 2012). Both the zooplankton abundance (16.8 to 1,076 ind.…”

Latitudinal variations in the abundance, biomass, taxonomic composition and estimated production of epipelagic mesozooplankton along the 155°E longitude in the western North Pacific during spring

“…Other north/south transects in the North Pacific indicated that zooplankton abundance is lower at low latitudes and is higher at high latitudes (Yokoi et al, 2008;Matsuno and Yamaguchi, 2010;Saito et al, 2011;Fukuda et al, 2012). Where the zooplankton abundance is the lowest, the number of species and species diversity are reported to be higher in the subtropical and tropical oceans for various zooplankton taxa, i.e., Copepoda (Heinrich, 1969), Euphausiacea, Pteropoda and Chaetognatha (Fager and McGowan, 1963).…”

The importance of hydrothermal venting to water-column secondary production in the northeast Pacific

“…Most studies of heterotrophic biomass or production patterns in the open ocean focus almost exclusively on the top 250 m of the water column (Sabates et al, 1989;Brodeur and Ware, 1992;Mackas, 1995;Brodeur et al, 1996;Young et al, 1996;Sugimoto and Tadokoro, 1997;Goldblatt et al, 1999;Nagasawa, 2000a, b;Uye et al, 2000;Stock and Dunne, 2010;Fukuda et al, 2012;Huo et al, 2012). Much of this research is based on the assumption that virtually all heterotrophic production in the open ocean is derived from top-down nutrient input and, therefore, only the organisms which are migrating above thermocline depth have direct access to nutrition from primary producers.…”