Climate change may not kill phytoplankton, studies show
Tiny water plants can adapt to warmer world, but there are limits
Most of the focus at the United Nations Climate Change Conference in Paris is on working toward agreements on how to address climate change, and what a changing planet might mean for humans.
But CBC Radio science columnist Torah Kachur has been following the conference and exploring new research about tiny water-dwelling plants called phytoplankton — which are being used to measure the effects of our warming world.
What are phytoplankton?
Phytoplankton are a large variety of aquatic microoganisms that perform photosynthesis, just like land-based plants do.
They use energy from the sun and convert it into food for the entire food chain. This makes them the primary producers of biomass in the oceans — pretty much all the edible carbon in the ocean comes from the action of these small creatures.
Why are they important for understanding climate change?
For starters, they absorb just as much carbon dioxide as all the tropical rainforests on land.
You've likely heard that one of the major drivers of climate change and increased carbon dioxide levels is deforestation, because we have lost plants that use up carbon dioxide in the air.
Phytoplankton's ability to mop up carbon dioxide dissolved in the ocean can remove some of that greenhouse gas from circulation.
Not only that, but they are primary producers — which means if they are affected by rising ocean temperatures or acidity, the entire ecosystem will feel the impact.
What does the latest research say about the effect of climate change on phytoplankton?
That's been the focus of three papers, just published in the past week.
The first was published in the journal Science, and looked at data from the past 50 years. The paper's authors found one particular species of phytoplankton from the North Atlantic has thrived. In fact, its population has increased almost tenfold since 1965.
That's an incredibly surprising finding for the researchers. It has long been thought that organisms like these would be particularly sensitive to the increase in acidity that is measured in the oceans today.
That's because they have hard shells made from chalk, which doesn't form as well when acidity is higher.
But it turns out they haven't been impacted by the higher acid content in the oceans — or at least not yet.
Scientists also know phytoplankton populations bloomed like this during Earth's interglacial periods. Based on that, the authors suggest a big climactic shift is already underway, and that is not likely to be good for us.
Does that mean good news for phytoplankton, bad news for humans?
Maybe, but these little creatures continue to surprise us. Just like it was believed rising acidity would strongly affect their survival, it was also thought that rising temperatures would be especially damaging to these cells.
Most of our understanding of climate change comes from empirical and experimental evidence, used together with theoretical modeling to try to put it all together.
And some other recent research on phytoplankton may influence that modelling.
In another study also published this week, researchers like Daniel Padfield from the University of Exeter explored temperature adaptations of plankton. And he says they adapted quickly.
"At 33 degrees centigrade, which is the highest temperature where they were stressed out, they initially grew below what we would expect," he said.
"However, after just 45 days, they evolved increased growth rates. So essentially, they increased their thermal tolerance, so the range of temperatures in which they're capable of surviving, after only 45 days."
Now the researchers are trying to figure out how exactly they do that.
But it bodes well for the future — or at least a future where average temperatures rise by no more than two degrees — because the phytoplankton will still be around to produce oxygen.
Now climatologists can incorporate this hard evidence into their models to put together a cohesive picture. And most importantly, they can make better predictions of the effects changing climate will have on the planet.
Could phytoplankton's ability to adapt be an ally in efforts to curb the effects of climate change?
Only up to a point. In a third study published this week, in the Bulletin of Mathematical Biology, researchers from the University of Leicester predicted that a six-degree rise in ocean temperature will prevent phytoplankton from surviving. That would mean the loss of the oxygen they produce through photosynthesis.
Two-thirds of our atmospheric oxygen comes from the photosynthesis of marine life, so if the phytoplankton die, it's fairly likely we do too.
However, that six-degree rise in global ocean temperature is beyond most of the predictions from existing climate models. And the researchers may have chosen it to illustrate the most extreme consequences.
But it does show that there are limits to what phytoplankton can do for us. So while nature constantly can make us marvel at its ability to adapt, science shows that we can't count on phytoplankton to fix the problem.
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