Transcriptomic profiling of an oceanic diatom adapted to Cu deficiency

Enhanced vertical stratification brought about by warming of the ocean surface is expected to reduce vertical circulation and nutrient input with knock-on effects for phytoplankton. Increased nutrient limitation is one predicted outcome, but the response of phytoplankton is uncertain because long-term adaptation to nutrient limitation has not been studied. We used Cu as a model catalytic nutrient to explore the adaptive response of an oceanic diatom to continuous nutrient deprivation. Thalassiosira oceanica was maintained under Cu-limiting and sufficient conditions for more than 2000 generations and the evolved populations evaluated for physiological traits in a reciprocal transplant experiment. Adaptation to low Cu concentration increased Cu use efficiency, so that under Cu-limiting conditions T. oceanica maintained significantly faster rates of net C assimilation and growth than the control and ancestral populations. Examination of low Cu-adapted (LCuA) and control Cu-adapted (CCuA) Thalassiosira oceanica cells, in triplicate, using illumina HiSeq 3000