Two recent studies reveal that some ocean plankton are less capable of adapting to global warming than they were in the past. This poses a serious threat to vast sections of marine life and raises concerns about the stability of the ocean ecosystem. For years, scientists have understood that phytoplankton—microscopic plants floating passively in the sea while absorbing sunlight and nutrients—form the foundation of the marine food web. From tiny fish to massive whales, all ocean creatures depend on phytoplankton for sustenance. However, researchers have faced challenges in predicting how plankton will respond to the rapidly accelerating effects of climate change.
In fact, record of global temperatures is so hot that there’s an 80 percent chance it will exceed the 1.5 C threshold agreed to by nations at the Paris summit in 2015. This is much sooner than scientists predicted, which raises the question: Can life on the planet adapt quickly enough?
One important factor is phytoplankton’s ability to absorb carbon dioxide and store it in their cells. This is a key part of the ocean’s natural carbon cycle, which is responsible for absorbing more than a third of the atmospheric CO2 produced by humans.
So, we must know how well phytoplankton will be able to absorb future CO2 from the air, but we’ve needed more data about how they do this in the past. Our new research published today in Nature explored the ability of tiny marine organisms called plankton to adapt to climate change by studying their response to historical temperature changes.
We compared the historical response of two different types of plankton, focusing on how the shifts in their thermal niches (the area they occupy) responded to climate change. The results showed that a type of zooplankton, which makes up about half of the global plankton community, was unable to keep pace with rapid temperature rises in the past. This means that if we experience a sudden and dramatic global warming event, these species could be at serious risk of extinction.
Another type of plankton, meanwhile, was able to adapt. It’s a bit like how people’s bodies respond to exercise—the fitter a person is, the easier it is for them to adapt to extreme conditions. The results show that this group of plankton was able to adjust to recent warming, but it did not keep up with the pace of global temperatures that we are experiencing now.
These results are particularly worrying given that the world’s oceans are now averaging 1.44 degrees Celsius warmer than they were in the pre-industrial period, and there is no guarantee that they will be able to adapt to future climate changes at this rate. In addition to this threat to marine biodiversity, this finding also has implications for the global carbon cycling process.