Effect of ice algal community on the increase of chlorophyll a concentration during spring in coastal water of the Sea of Okhotsk

• Main Authors: Satoru Taguchi, Fumio Satoh, Soshi Hamaoka, Mitsuo Ikeda, Masao Ishikawa, Kunio Shirasawa
• Format: Report
• Language: English
• Published: Soka University 2000
• Subjects: diatom; ice algae; size fractionation; absorption coefficient; Okhotsk; Polar bioscience; Sea ice
• Online Access: https://nipr.repo.nii.ac.jp/?action=repository_uri&item_id=6142; http://id.nii.ac.jp/1291/00006142/; https://nipr.repo.nii.ac.jp/?action=repository_action_common_download&item_id=6142&item_no=1&attribute_id=18&file_no=1

A seasonal study of size fractionated chlorophyll α concentration was conducted weekly in Monbetsu Harbor from October 1996 to November 1997 to investigate the annually persistent occurrence of the spring peak of the chlorophyll α concentration in the >10μm size fraction immediately after the retreat of sea ice, as described by K. Hamasaki et al. (Plankton Biol. Ecol., 45,151,1998). Species composition of natural phytoplankton assemblages was also investigated to study whether phytoplankton or ice algae were responsible for the spring peak in the coastal water. The spring peak occurred immediately after the retreat of sea ice but timing of the occurrence was different between the stations occupied in the present study. The spatial heterogenity in occurrence of the spring peak seemed to be related to the sea ice distribution between the stations. New sea ice provided only a small supply of ice algae due to the relatively short growth period inside of the harbor. Large ice floes provided for a large supply of ice algae due to the long growth period outside of the harbor. The magnitude of the spring peak was related to sea ice growth. However, those ice algae seemed to sink to the bottom with little contribution to phytoplankton assemblage in the harbor, while ice algae contributed significantly to the spring peak outside of the harbor. Species composition revealed relatively fast response of phytoplankton to the environmental change after the disappearance of sea ice. Surface assemblages of phytoplankton including ice algae seemed to respond fully to the regional optical condition by changing in the species composition.