Abstract
Ocean acidification (OA), induced by rapid anthropogenic CO2
rise and its dissolution in seawater, is known to have consequences for
marine organisms. However, knowledge on the evolutionary responses of
phytoplankton to OA has been poorly studied. Here we examined the
coccolithophore Gephyrocapsa oceanica, while growing it for 2000 generations under ambient and elevated CO2
levels. While OA stimulated growth in the earlier selection period
(from generations ~ 700 to ~ 1550), it reduced it in the later selection
period up to 2000 generations. Similarly, stimulated production of
particulate organic carbon and nitrogen reduced with increasing
selection period and decreased under OA up to 2000 generations. The
specific adaptation of growth to OA disappeared in generations 1700 to
2000 when compared with that at 1000 generations. Both phenotypic
plasticity and fitness decreased within selection time, suggesting that
the species' resilience to OA decreased after 2000 generations under
high CO2 selection.