Prochlorococcus, a phytoplankton responsible for about 20% of Earth's oxygen, is at risk of halving by the end of the 21st century due to global boiling!
Hello, this is Tasuki.
The summer of 2025 was too hot. Now that we are in the middle of October 2025, the temperature has dropped, and it has finally become comfortable enough to live without air conditioning.
As I write this article, the maximum temperature is 25 degrees Celsius. There was even a forecast for snow in Hokkaido.
The first snowcap of the season was observed on Mount Fuji on October 23, 2025. This was 21 days later than an average year and 15 days earlier than in 2024. The observation on October 23 was the fourth latest on record.
How is everyone doing?
In response to the abnormal heat in 2025, the Japan Meteorological Agency (JMA) is reportedly considering new terms for weather forecasts.
The JMA has decided to declare days with a maximum temperature of 25 degrees or higher as a "summer day," 30 degrees or higher as a "midsummer day," and 35 degrees or higher as an "extremely hot day." In 2007, the JMA added "extremely hot day" as a "forecast term" used in weather reports, and it is now used in daily life.
Given the background of consecutive days where the maximum temperature exceeded 40 degrees in the summer of 2025, JMA Director-General Ryuichi Nomura announced at a press conference on September 17, 2025, that they are considering a new "forecast term" for days of 40 degrees or higher. He explained that "scorching hot day" is the leading candidate and that they hope to start using it in weather forecasts as early as the summer of 2026.
According to the JMA, the number of locations reaching 40 degrees or higher has been increasing since 2010. In 2025, 40 degrees or higher was recorded at a total of 30 locations out of 914 nationwide, including a record-high temperature of 41.8 degrees in Isesaki City, Gunma Prefecture, on August 5.
It is actually quite surprising that there wasn't a "scorching hot day" term before.
This disaster-level heat is also said to be continuously affecting the phytoplankton that produce the oxygen essential for our survival.
The phytoplankton "Prochlorococcus" is about 1 micrometer in size and is thought to inhabit about 75% of the sunlit surface ocean, making it the most abundant photosynthetic organism on Earth.
A research group including the University of Washington in the United States has revealed a prediction that "Prochlorococcus," a type of phytoplankton that produces about 20% of the Earth's oxygen through photosynthesis, could potentially be halved by the end of the 21st century due to rising seawater temperatures caused by global boiling.It has also been pointed out that the rapid and continuous decline of "Prochlorococcus," which has supported the Earth's ecosystem, could deal a major blow to a wide range of areas, including marine resources.
On September 8, 2025, this paper was published in the British scientific journal [Nature Microbiology].
In this article, I would like to explain what the phytoplankton "Prochlorococcus" is, what characteristics it has, and what kind of impact it will continue to have on us in the future.
The phytoplankton "Prochlorococcus" is at risk of halving by the end of the 21st century. How much is it expected to continue to decline?
It was previously thought that the phytoplankton "Prochlorococcus" breeds in warm waters and that its habitat would expand due to global boiling.
Between 2010 and 2023, the research group collected a total of about 800 billion phytoplankton during 90 voyages in the subtropical and tropical Pacific Ocean. They analyzed the state of the phytoplankton "Prochlorococcus" and water temperatures.
As a result, it was found that while the speed at which the phytoplankton "Prochlorococcus" grows and divides becomes more active as water temperatures rise, the speed of division drops significantly once it exceeds 28 degrees.
It is predicted that if sufficient measures against global boiling are not taken, seawater temperatures in the subtropics and tropics will routinely exceed 30 degrees. It is assumed that as a result, the phytoplankton "Prochlorococcus" will continue to decline by 17–51% compared to today, and oxygen supply could potentially decrease by 3–10%.
Research data has also arrived indicating that the social issue of the phytoplankton 'Prochlorococcus' is being hindered in its growth by the influence of harmful substances emitted from plastic waste leaked into the ocean.
Dr. François Ribalet of the University of Washington expressed his sense of crisis, saying,
'In the short term, I think other types of phytoplankton can compensate for the oxygen supply work, but they continue to be subjected to many stresses such as ocean acidification and plastic waste. The time to prevent the worst-case scenario is significantly limited.'
he added.
Other news related to global boiling
The harvest of apples in Aomori Prefecture in 2025 is expected to be 372,300 tons. This is on par with the 2024 results (370,500 tons), but it looks like it will fall below 400,000 tons for the third consecutive year.
Aomori Prefecture accounts for approximately 60% of the total apple harvest in Japan. The apple harvest had been over 400,000 tons since 2012, but it has fallen below 400,000 tons since 2023, and according to the prefectural Apple and Fruit Tree Division, this is the first time that the apple harvest has fallen below 400,000 tons at the forecast stage since Aomori Prefecture began announcing forecasts.
According to the prefectural Apple and Fruit Tree Division, the reasons are that branches were broken by the weight of winter snow in 2025, resulting in fewer fruits, and that there was little rain during the summer, leading to a trend of smaller apple fruits.
The breakdown of the expected apple harvest is 233,300 tons for Fuji, 30,000 tons for Ohrin, 26,900 tons for Jonagold, 19,300 tons for Tsugaru, and 62,800 tons for other apples.
In this way, global boiling continues to affect everything, from the phytoplankton 'Prochlorococcus' to apples.
Will the rich Earth of the past never return?
What can we do to stop this global boiling, even if just a little?
Especially regarding the phytoplankton 'Prochlorococcus', there is nothing I can do.
I cannot do anything, but I would like to help ensure that the number of 'Prochlorococcus' phytoplankton does not decrease, through this article.
