Suppose that we could watch twenty generations of whales or sharks adapting to climate change -- measuring how they evolve and how their biology changes as temperatures and carbon dioxide levels rise. That could tell us a lot about how resilient life in the oceans might be to a warmer world. But it would also take hundreds of years -- not very useful to scientists or policymakers trying to understand our warming world today., a tiny and humble sea creature near the bottom of the food web.
A team of six scientists, led by University of Vermont biologist Melissa Pespeni and postdoctoral scientist Reid Brennan, did just that: in a first-of-its kind laboratory experiment, they exposed thousands of copepods to the high temperatures and high carbon dioxide levels that are predicted for the future of the oceans. And watched as twenty generations passed.
The complexity --"it's a caution, really," Pespeni says -- comes from the team's observation of what happened to the copepods that were returned to the baseline conditions. These creatures revealed the hidden cost of the earlier twenty generations of adaptation.
"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?" Pespeni wonders. Copepods are among a broad group of species predicted to be resilient to rapid climate change -- and this new study, supported by the National Science Foundation, upholds that view.
"But we need to be careful of overly simple models -- about how well species will do and which ones will persist into the future -- that look at just one variable," said Reid Brennan who completed this study in Melissa Pespeni's lab at the University of Vermont and is now at the GEOMAR Helmholtz Centre for Ocean Research in Kiel, Germany.