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Aquatic Microbial Ecology

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AME 46:203-207 (2007)  -  doi:10.3354/ame046203

Size distribution and biomass of nanoflagellates in meso- and bathypelagic layers of the subarctic Pacific

Hideki Fukuda1,*, Rumi Sohrin2, Toshi Nagata3, Isao Koike1

1Ocean Research Institute, University of Tokyo,1-15-1, Minamidai, Nakano, Tokyo 164-8639, Japan
2Faculty of Science, Shizuoka University, 836 Ohya, Shizuoka-shi, Shizuoka 422-8529, Japan
3Center for Ecological Research, Kyoto University, Kamitanakami-Hirano, Otsu, Shiga 520-2113, Japan

ABSTRACT: We examined the abundance, cell size, and biomass of nanoflagellates throughout the water column and compared the results with data on prokaryote biomass and production at 6 sampling stations in the subarctic Pacific and the Bering Sea. For the upper (0–100 m), mesopelagic (100–1000 m), and bathypelagic layers (1000–3500 m), the integrated biomass of nanoflagellates was 310 ± 290, 130 ± 56, and 31 ± 17 mg C m–2 (mean ± SD; n = 6), respectively, accounting for 4.8 ± 4.5, 3.2 ± 4.8, and 0.83 ± 0.67% of prokaryote biomass. The turnover time of prokaryotes (biomass/ production) was significantly negatively correlated with the biomass of flagellates in the upper and bathypelagic waters, but the correlation was not significant in the mesopelagic layer. Assuming that nanoflagellates clear water 5 × 105 times greater than their own cell volume per hour, we estimated that grazing by nanoflagellates could consume 70 ± 46 and 48 ± 25% (mean ± SD; n = 6) of prokaryote production in meso- and bathypelagic layers, respectively. The above results suggest that nanoflagellates play a potentially significant role as consumers of prokaryotes in deep Pacific waters of subarctic regions.

KEY WORDS: Heterotrophic nanoflagellates · Marine bacteria · Deep Sea · Leucine incorporation · Subarctic Pacific · Bering Sea · Microbial food web · Sinking flux

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