Adaptation of a marine diatom to ocean acidification and warming reveals constraints and trade-offs

Ocean acidification andwarming are recognized as two major anthropogenic perturbations of the modern ocean. However, little is known about the adaptive response of phytoplankton to them. Here we examine the adaptation of a marine diatom Thalassiosira weissflogii to ocean acidification in combination with ocean warming. Our results show that ocean warming have a greater effect than acidification on the growth of T. weissflogii over the long-term selection experiment (similar to 380 generations), as well as many temperature response traits (e.g., optimum-temperatures for photosynthesis, maximal net photosynthetic oxygen evolution rates, activation energy) in thermal reaction norm. These results suggest that ocean warming is the main driver for the evolution of the marine diatom T. weissflogii, rather than oceanacidification. However, the evolution resulting from warming can be constrained by ocean acidification, where ocean warming did not impose any effects at high CO2 level. Furthermore, adaptations to ocean warming alone or to the combination of ocean acidification and warming come with trade-offs by inhibiting photochemical performances. The constrains and trade-offs associated with the adaptation to ocean acidification and warming demonstrated in this study, should be considered for parameterizing evolutionary responses in eco-evolutionary models of phytoplankton dynamics in a future ocean. (C) 2021 Elsevier B.V. All rights reserved.

Automated summary

The study found that ocean warming has a greater impact on the growth of marine diatom Thalassiosira weissflogii over long-term selection experiments compared to ocean acidification. Many temperature response traits were influenced by ocean warming, indicating that it is the main driver for the evolution of T. weissflogii. However, adaptations resulting from warming can be constrained by ocean acidification, leading to trade-offs in photochemical performances.