Why You Should Care About Phytoplankotn

Photosynthesis, as you may recall from high school Biology class, is the process in which plants use the Sun’s energy to convert water and carbon dioxide into glucose and oxygen.[1] Plants use the glucose to grow and survive. Oxygen, for the most part, is simply a bi-product which the plants release into the atmosphere.

About 50% of the world’s oxygen comes from plant life in the oceans—most of it from phytoplankton, which are microscopic organisms like bacteria and algae which are capable of photosynthesis. And about 40% of that oxygen—or about 20% of all oxygen on Earth—is generated by the world’s smallest and most numerous photosynthetic organism, a form of phytoplankton called Prochlorococcus. Since we breathe oxygen, it’s a good thing for us that Prochlorococcus exists.

But it’s even more important for the oceanic food chain, since phytoplankton like Prochlorococcus make up the base of that food chain. Many species eat Prochlorococcus, and many other species, like fish, eat the species that eat Prochlorococcus. Without it, populations of fish and other sea creatures could decline significantly.

Unfortunately, a new study published in Nature Microbiology found that Prochlorococcus doesn’t like water temperatures above 82 degrees (Fahrenheit). In fact, at water temperatures higher than that, Prochlorococcus populations could decrease by as much as 50% by the end of this century, potentially disrupting both atmospheric oxygen levels and the oceanic food chain. But because climate change is warming both the air and water, the trend in tropical and subtropical waters is for temperatures to regularly exceed 86 degrees by 2100.

To learn more about what climate change is, how it is impacting our world, and how it might be fulfilling biblical prophecy, please read Chapter 11 of my book, Beyond Blind Faith, entitled “Apocalypse Soon.” You can read it in its entirety for free on this website. Just click here, or click on “Don’s Books” at the top of this page and scroll down to the “List of Contents” under my book, Beyond Blind Faith.

[1]. This blog entry is based in part on the following sources:

“Warming Seas Pose Risk For Plankton,” by Annika Hammerschlag, Associated Press, appearing in the Dallas Morning News, September 9, 2025, page 5A.

“Predators Set Range for the Ocean’s Most Abundant Phytoplankton,” from the Archive for Prochlorococcus, by The Ocean Carbon and Biogeochemistry (OCB) program, found at https://www.us-ocb.org/tag/prochlorococcus/.

“How much oxygen comes from the ocean?,” National Ocean Service, National Oceanic and Atmospheric Administration, found at https://oceanservice.noaa.gov/facts/ocean-oxygen.html