Siliceous cysts from Kita-no-seto Strait,north of Syowa Station, Antarctica

Abstract

Siliceous cysts of 29 different morphological shapes were observed in the sea ice and sea water at the Kita-no-seto Strait, north of Syowa Station, Antarctica. Twenty species of those were newly discovered in the Antarctic waters. Cysts collected were in the size range of 3 to 10μm. They were tentatively classified into four groups based on their morphological characteristics; Sphaerica, Ovoidea, Hemisphaerica, and Tri/quadrihedra. Twelve cysts representative of each group and a cyst of Paraphysomonas imperforata confirmed newly were described. Cysts appeared from March to May, and in December (summer to autumn season) and the species diversity was highest in December with 18 species. Among 29 species, 20 appeared in the sea ice, eight in both sea ice and sea water, and one in sea water only. Main habitat of them seemed to be the brine pockets or channels of the sea ice.