Proc. NIPR Symp. Polar Biol., 11, 22-32, 1998 PHOTOSYNTHETIC PIGMENT COMPOSITION OF ICE ALGAL AND PHYTOPLANKTON ASSEMBLAGES IN EARLY SPRING IN SAROMA KO LAGOON, HOKKAIDO, JAPAN Yasuhiro KASHINO' , Kumiko FUJIMOTO~ Akemi AKAMATSU ' , Hiroyuki KOIKE', Kazuhiko SATOH' and Sakae KUDOH~ Faculty of Science, Department of Life Science, Himeji Institute of Technology, Harimu Science Garden City, 678-1297 National Institute of Polar Research, 9-10, Kaga 1-chome, Itahashi-ku, Tokyo 173-8515 Abstract: Ice algae were collected from sea ice of 35 cm thickness at Saroma KO lagoon in early February, 1996. The sea ice was sectioned into 5 cm height intervals from the bottom so as to separate ice algae according to vertical distribution. Phytoplankton were also harvested at the same site in mid-April, 1996, a few days after the sea ice disappeared. Photosynthetic pigments of ice algae and phyto- planktonic algae were analyzed by reverse-phase HPLC (high performance liquid chromatography). Chlorophyll a, c, /?-carotene, and several kind of carotenoids, such as fucoxanthin, diadinoxanthin or diatoxanthin, were detected, but chlorophyll b was not recognized, suggesting that diatom species were predominant in ice algae and phytoplanktonic algae. The pigment composition of ice algae changed according to their vertical distribution. The ratios of chlorophyll c and carotenoids to chlorophyll a in ice algae harvested from the top of the sea ice were higher than those of ice algae collected from the lower position, in other words, ice algae in the lower position, i.e., where they experienced less light decreased the ratio. This suggests that ice algae adopted very peculiar light-shade adaptation, because vascular plant or green algae have the opposite response so that they decrease the ratio of auxiliary pigments to chlorophyll a with increasing light intensity. Pigment composition of phytoplanktonic algae resembled that of ice algae collected from the uppermost portion of sea ice. key words: ice algae, photosynthetic pigments, reverse-phase HPLC, diatom, light-shade adaptation Introduction Massive ice algal growth is commonly observed in brine pockets or channels form- ed mainly in the bottom of sea ice (WELCH and BERGMANN, 1989; POULIN, 1990). Accordingly, ice algae have to perform photosynthesis under very severe circumstances such as sub-zero temperature and low light intensity. Light intensity at the bottom of sea ice where ice algae mainly exist is severely lowered, below 1 % compared to the light Abbreviations: Chl; chlorophyll, HPLC; high performance liquid chromatography, LHC; light harvesting complex, PS I and PS 11; photosystem I and 11, PSU; photosynthetic unit, RT; retention time.