MEPS 204:289-292 (2000)  -  doi:10.3354/meps204289

Seasonal variation of two different heterotrophic bacterial assemblages in subarctic coastal seawater

Mitsuru Yanada*, Taichi Yokokawa, Choon Weng Lee, Hitoshi Tanaka, Isao Kudo, Yoshiaki Maita

Division of Marine Environment and Resources, Graduate School of Fisheries Science, Hokkaido University, Hakodate 041-8611, Japan

ABSTRACT: The numbers of heterotrophic bacteria in the subarctic coastal seawater of Funka Bay, Japan, were measured by flow cytometry, and 2 different bacterial assemblages were detected: cells with low DNA content (Group I) and cells with high DNA content (Group II). Although the abundances of both Group I and Group II bacteria showed similar regression slopes against seawater temperature (p > 0.7), Group II bacteria consisted of high growth capacity cells, growing actively in an enriched incubation experiment, whereas Group I bacteria consisted of inactive cells, not responding to an enriched environment. The seasonal variation of the total bacterial abundance observed in Funka Bay was caused almost exclusively by Group II bacteria.

KEY WORDS: Heterotrophic bacteria · Flow cytometry · Seasonal variation · Subarctic coastal seawater

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