Prolonged darkness and diatom mortality I: Marine Antarctic species

Abstract

The effect of prolonged periods of darkness (up to 10 months) was investigated in the diatom species Thalassiosira antarctica Comber, T. tumida (Janisch) Hasle, Porosira pseudodenticulata (Hustedt) Jousé, Proboscia inermis (Castracane) Jordan and Ligowski and Fragilariopsis kerguelensis (O'Maera) Hustedt isolated from the Southern Ocean. Sudden darkness did not induce resting spore formation. All species survived in their vegetative stage. High levels of photosynthesis were resumed in T. antarctica, T. tumida and P. inermis upon re-exposure to light at all times tested during a 3 month dark period. Cellular chlorophyll a, carbon and nitrogen decreased at the beginning of the dark period and remained more or less stable suggestive of a low maintenance respiration. Species specific survival times varied from less than 4 months up to 9 months. After returning to the former light regime during the species specific survival times T. antarctica, T. tumida, P. pseudodenticulata and P. inermis began growing at rates similar to those in the pre-dark phase.