The Revelator discusses whether climate change will threaten Earth’s other ‘lung’? Phytoplankton produce half of the oxygen in our atmosphere, but understanding how they respond to climate change is complicated and critically important. Ask someone on the street about the importance of the Amazon, and there’s a reasonable chance the response will include an understanding that forests play an essential role in storing and cycling global carbon. Follow that question with another on the importance of ocean phytoplankton, and there are good odds on it being met with a shrug.
Yet the significance of ocean phytoplankton is nearly impossible to overstate.
Drifting in the top layer of the world’s oceans, phytoplankton are a diverse group of microscopic, photosynthetic organisms. Most are single-celled algae, some are bacteria, and others are classified as protists – neither plant nor animal. Phytoplankton are estimated to produce nearly half the daily oxygen in our atmosphere, and as the basis of the ocean food web, sustain all major marine life forms. When they die, a percentage sink to the ocean floor, sequestering as much carbon as all terrestrial plants.
A decade ago, Canadian researchers made headlines with an alarming study estimating ocean phytoplankton populations had dropped 40% since 1950, and were continuing to decline at a rate of around 1% per year, with ocean warming from climate change suspected. The findings were hotly debated, and in the years since, a more nuanced yet still alarming picture of how phytoplankton will fare under climate change has begun to emerge.
In a 2015 study by two of the same Canadian researchers, projections of phytoplankton concentrations are described as “highly divergent.”
A study published in Nature in 2018, by an international team of researchers, also suggests that increased acidification could interfere with a poorly understood mechanism that allows diatoms to acquire iron — an essential nutrient for the algae.