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

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 x 10 5 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.