According to new research published in the journal Nature Communications, although ocean life could possibly adapt to major climate changes, there may be unforeseen costs to quickly evolving in a suddenly-hot world. Thus, while plasticity may facilitate initial survival in global change conditions, it could erode after populations adapted, limiting resilience to new stressors and previously benign environments.
In order to assess how marine organisms adapt to climate change over several generations, the scientists used copepods (Acartia tonsa) as a case study. Since this tiny and humble sea creature reproduces, matures, and creates a new generation in about twenty days, it takes less than one year for twenty generations to pass.
The scientists exposed thousands of copepods to the high temperatures and carbon dioxide levels that are predicted for the future of the oceans, and examined what happened to these creatures as twenty generations passed. Afterwards, they took some of the marine organisms and returned them to the temperature and carbon dioxide levels that the first generation started in, and observed them as three more generations passed.
The results showed that these creatures have the genetic capacity to adapt over twenty generations, evolving to maintain their fitness in radically-changed environments (a process called “phenotypic plasticity”). The researchers observed many changes in the copepods’ genes related to how they managed heat stress, grew their skeletons in more acidic waters, and produced energy, suggesting that they can be highly resilient to rapid warming and acidification.
However, the flexibility that helped the copepods evolve over twenty generations seemed to be eroded when they tried to return them to what had previously been their normal environment. Brought to the initial temperatures and carbon dioxide concentrations, the copepods were less healthy and produced smaller populations. Although they were able, after three generations, to re-evolve to their ancestral conditions, the marine organisms nevertheless lost the ability to tolerate limited food supply and showed less resilience to new forms of stress.
“If copepods or other creatures have to go down this adaptive path – and spend some of their genetic variation to deal with climate change – will they be able to tolerate some new environmental stressor, some other change in the environment?” wondered study lead author Melissa Pespeni, a biologist at the University of Vermont. This study suggests that it may not be so easy.