Density and distribution of bacterioplankton and planktonic ciliates in the Bering Sea and North Pacific

• Published in: Journal of Plankton Research
• Main Authors: Sorokin, Yu. I., Sorokin, P. Yu., Mamaeva, T. I.
• Format: Text
• Language: English
• Published: Oxford University Press 1996
• Subjects: ORIGINAL ARTICLES; Bering Sea; Pacific; Subarctic
• Online Access: http://plankt.oxfordjournals.org/cgi/content/short/18/1/1; https://doi.org/10.1093/plankt/18.1.1

The total number of planktonic bacteria in the upper mixed layer of the Bering Sea during the late spring-early summer period ranged between 1 and {small tilde}4 × 106 ml−1 (biomass 10–40mg C m−3). In the northern Pacific, along 47–526N, the corresponding characteristics of the bacterioplankton density in the upper mixed water layer were: total number 1–2 × 106 cells ml−1 and biomass 15–46mg C m−3 Below the thermocline at 50–100 m, the density of bacterioplankton rapidly decreased. At 300 m depth, it stabilized at 0.1–0.2 × 106 cells ml−1. The integrated biomass of bacterioplankton in the open Bering Sea ranged between 1.2 and 3.6 g C m−2 (wet biomass 6–18 g m−2) Its production per day varied from 2 to 23 mg C m−3 days−1 in the upper 0–100 m. The numerical abundance of planktonic ciliates in this layer was estimated to be from 3 to l0 × 103 cells l−1, and in the northern Pacific from 0.4 to 4.5 × 103 l−2. Their populations were dominated by naked forms of Strombidium, Strombilidium and Tontonia . In some shelf areas, up to 40% of the total ciliate population was represented by the symbiotic ciliate Mesodinium rubrum . The data on the integrated biomass of basic groups of planktonic microheterotrophs are also presented, and their importance in the trophic relationships in pelagic communities of subarctic seas is discussed.