ABUNDANCE AND BIOMASS DISTRIBUTION OF MICROBIAL ASSEMBLAGES AT THE SURFACE IN THE OCEANIC PROVINCE OF ANTARCTIC OCEAN (14th Symposium on Polar Biology)

• Main Authors: イシヤマ ミチエ, ヒロミ ジュウロウ, タニムラ アツシ, カドタ サダミ, Michie ISHIYAMA, Juro HIROMI, Atsushi TANIMURA, Sadami KADOTA
• Format: Report
• Language: English
• Published: Proceeding 1993
• Subjects: Antarctic; The Antarctic; Indian; Antarctic Ocean; Antarc*; Polar Biology; Proceedings of the NIPR Symposium on Polar Biology
• Online Access: https://nipr.repo.nii.ac.jp/?action=repository_uri&item_id=5180; http://id.nii.ac.jp/1291/00005180/; https://nipr.repo.nii.ac.jp/?action=repository_action_common_download&item_id=5180&item_no=1&attribute_id=18&file_no=1

During the JARE-32 (the 32nd Japanese Antarctic Research Expedition) cruise, bacterioplankton, autotrophic and heterotrophic nanoplankton (2-20 μm in length), and microzooplankton (15-250 μm in length) were collected from the surface of the Indian and Australian sectors of Antarctic Ocean. The average abundance of bacterioplankton was 4.56×10^4 cells/ml, and the biomass was 0.25 mg C/m^3. The values of the autotrophic nanoplankton were 0.5×10^3 cells/ml and 2.27 mg C/m^3, respectively. There were 1.02×10^2 cells/ml of heterotrophic nanoplankton in abundance, and its biomass was 0.71 mg C/m^3. About 30% of the biomass of this assemblage was choanoflagellates. Average abundance and biomass of the microzooplankton were 1.62×10^3 inds./l and 3.78 mg C/m^3, respectively. A large portion of the abundance and biomass of microzooplankton was oligotrichs. Protozoans within micro-sized (15-250 μm) category which ingest preys similar to or larger than themselves were found where biomass ratio of nanoplankton to microzooplankton was low (<0.3). This may indicate adaptability of the protozoan to a severe food environment. The biomass (log-scale) decreased linearly with increasing individual body weight (log-scale) with a slope of -0.21. This result suggests that smaller protozoans such as heterotrophic nanoplankton and oligotrichs have an important role in the Antarctic Ocean's energy flow.