Streßphysiologie bei antarktischen Diatomeen:Ökophysiologische Untersuchungen zur Bedeutung von Prolin bei der Anpassung an hohe Salinitäten und tiefe Temperaturen.

Abstract

Four of totally nine examined antarctic ice diatoms have been exposed to a long-term experiment to give the proof that not only the sell size but also physiological properties are responsible for the vertical distribution of the ice diatoms in the ice column. Therefore Chaetoceros sp., Corethron pennatum, Amphiprora kufferathii and Nitzschia lecointei are compared with respect to some of their physiological characteristics in relation to their natural distribution: Chaetoceros sp. mainly occurs in the upper part and A. kufferathii at the bottom of the ice column; N. lecointei is spread within the ice but preferably more in the lower parts, whereas C. pennatum is mainly distributed in the open water. In the upper part of the ice life conditions are variable with low temperatures and high salinities. In comparison the conditions at the bottom of the ice column are stable. According to their occurrence in the ice column the ability of the four species to acclimatise varies: Chaetoceros sp. has to cope with highly variable conditions unlike A. kufferathii and C. pennatum. Physiological properties obtained with the mentioned experiment indicate that Chaetoceros sp. and N. lecointei best tolerate extreme life conditions compared to the other two species because they endure a greater range of temperature and salinity, e.g. up to 151 PSU (N. lecointei) and more than 196 PSU (Chaetoceros sp.). Additionally the accumulation pattern of the main osmolyte proline proves the species specific ability to acclimatise to cold temperatures and high salinities. But there are differences in the way of acclimatisation between N. lecointei and Chaetoceros sp.: the former accumulates proline and other organic osmolytes only to an amount of 40 mM at maximum whereas the latter is able to synthesise proline up to 4.5 M. The concentrations are reflected by different properties of the Pyrroline-5-carboxylate Reductase which is one of the proline synthesising enzymes.