title: Morphological adaptation of a planktonic diatom to growth in Antarctic sea ice.
abstract: Chaetoceros dichaetaEhrenberg is one of the most important planktonic diatom species in the Southern Ocean, making a significant contribution to the total biomass in the region. Our observations on both field and culture material have revealed the existence of a specialized form ofC. dichaetaadapted to living in sea ice. This sea ice form differs from the planktonic form by the shape and orientation of the setae and the aperture length between sibling cells. Thus, the diameter of the chain is equivalent to the apical axes of the cells and is accompanied by a two order of magnitude decrease in minimal space requirement. Here, we report for the first time on the extraordinary overwintering strategy of a planktonic diatom in sea ice facilitated by its rapid morphological adaptation to changing environmental conditions. This morphological plasticity enables it to thrive in the confined space of the sea ice brine matrix and retain its numerical dominance in recurrent growing seasons and has likely evolved to optimally exploit the dynamic ecosystem of the seasonally ice-covered seas of the Southern Ocean.
authors.affiliation: Department of Polar Biology and Oceanobiology, University of Lodz, Banacha 12, 90-237 Lodz, Poland.
authors.forename: Ryszard
authors.initials: R
authors.lastname: Ligowski
authors.affiliation: Department of Earth and Environmental Sciences, Faculty of Science, Yamagata University, Yamagata, 990-8560 Japan.
authors.forename: Richard W
authors.initials: RW
authors.lastname: Jordan
authors.affiliation: Alfred Wegener Institute for Polar and Marine Research, Am Handelshafen 12, 27570 Bremerhaven, Germany ; Norwegian Polar Institute, Fram Centre, 9296 Tromsø, Norway.
authors.forename: Philipp
authors.initials: P
authors.lastname: Assmy