{"id":60380,"date":"2025-09-12T21:57:08","date_gmt":"2025-09-12T21:57:08","guid":{"rendered":"https:\/\/www.europesays.com\/ie\/60380\/"},"modified":"2025-09-12T21:57:08","modified_gmt":"2025-09-12T21:57:08","slug":"the-oceans-most-abundant-life-form-may-not-survive-global-warming","status":"publish","type":"post","link":"https:\/\/www.europesays.com\/ie\/60380\/","title":{"rendered":"The Ocean\u2019s Most Abundant Life Form May Not Survive Global Warming"},"content":{"rendered":"

\t\t\"Cruise<\/a>The lines on the map are cruise tracks, overlaying temperature. The water in yellow areas hovers around 86 degrees while the temperature at the poles is closer to 32. Researchers cataloged Prochlorococcus abundance using SeaFlow continuous flow cytometry along the path of the lines. Credit: Fran\u00e7ois Ribalet\/University of Washington<\/p>\n

Tiny ocean microbes called Prochlorococcus, once thought to be climate survivors, may struggle as seas warm.<\/strong><\/p>\n

These cyanobacteria drive 5% of Earth\u2019s photosynthesis and underpin much of the marine food web. A decade of research shows they thrive only within a narrow temperature range, and warming oceans could slash their populations by up to 50% in tropical waters.<\/p>\n

Ocean\u2019s Microscopic Powerhouses<\/p>\n

Among the smallest organisms in the sea are microscopic, single-celled creatures known as Prochlorococcus. These microbes belong to the cyanobacteria group, also called blue-green algae, and they form the base of the food supply for animals throughout the marine food web. Today, more than 75% of the sunlit surface ocean is filled with Prochlorococcus, yet scientists warn that warming waters may soon become too hot for them to thrive.<\/p>\n

Prochlorococcus holds the title as the most abundant photosynthesizing organism<\/a> in the ocean and is responsible for about 5% of all photosynthesis on Earth. Because it naturally flourishes in tropical waters, researchers once assumed it would handle climate change with ease. However, new evidence shows that the microbe grows best at temperatures between 66 and 86 degrees and struggles to survive above that range. Climate projections suggest that within the next 75 years, many tropical and subtropical regions will surpass this limit.<\/p>\n

\"Prochlorococcus<\/a>This image, captured by an electron microscope, displays individual Prochlorococcus cells. Each blob is a microbe, measuring just 500 nanometers in diameter. For reference, the width of a single human hair is around 100,000 nanometers. Credit: Natalie Kellogg\/University of Washington
\nGlobal Food Chain at Risk<\/p>\n

\u201cFor a long time, scientists thought Prochlorococcus was going to do great in the future, but in the warmest regions, they aren\u2019t doing that well, which means that there is going to be less carbon \u2014 less food \u2014 for the rest of the marine food web,\u201d said Fran\u00e7ois Ribalet, a University of Washington research associate professor of oceanography, who led the study.<\/p>\n

Their results were published in Nature Microbiology on September 8.<\/p>\n

Massive Field Studies at Sea<\/p>\n

In the past 10 years, Ribalet and colleagues have embarked on close to 100 research cruises to study Prochlorococcus. His team has analyzed approximately 800 billion Prochlorococcus-sized cells across 150,000 miles around the world to figure out how they are doing and whether they can adapt.<\/p>\n

\u201cI had really basic questions,\u201d Ribalet said. \u201cAre they happy when it\u2019s warm? Or are they not happy when it\u2019s warm?\u201d Most of the data comes from cells grown in culture, in a lab setting, but Ribalet wanted to observe them in their natural ocean environment. Using a continuous flow cytometer \u2014 called SeaFlow<\/a> \u2014 they fired a laser through the water to measure cell type and size. They then built a statistical model to monitor cell growth in real time, without disturbing the microbes.<\/p>\n

\"Thomas<\/a>Sunset from the research vessel Thomas G. Thompson, which housed the SeaFlow flow cytometer during data collection cruises. Credit: Kathy Newer\/University of Washington
\nTemperature: The Decisive Factor<\/p>\n

Results showed that the rate of cell division varies with latitude, possibly due to the amount of nutrients available, sunlight or temperature. The researchers ruled out nutrient levels and sunlight before zeroing in on temperature. Prochlorococcus multiply most efficiently in water that is between 66 and 84 degrees, but above 86, rates of cell division plummeted, falling to just one-third of the rate observed at 66 degrees. Cell abundance followed the same trend.<\/p>\n

Living on Almost Nothing<\/p>\n

In the ocean, mixing transports most nutrients to the surface from the deep. This occurs more slowly in warm water, and surface waters in the warmest regions of the ocean are nutrient-scarce. Cyanobacteria are one of the few microbes that have adapted to live in these conditions.<\/p>\n

\u201cOffshore in the tropics, the water is this bright beautiful blue because there\u2019s very little in it, aside from Prochlorococcus,\u201d Ribalet said. The microbes can survive in these areas because they require very little food, being so small. Their activity supports most of the marine food chain, from small aquatic herbivores to whales.<\/p>\n

\"Thomas<\/a>The crew at work during a research cruise aboard the Thomas G. Thompson. The device on the left collects water samples from different depths. The SeaFlow flow cytometer was also aboard, but not pictured here. Credit: Kathy Newer\/University of Washington
\nEvolutionary Trade-Offs<\/p>\n

Over millions of years, Prochlorococcus has perfected the ability to do more with less, shedding genes it didn\u2019t need and keeping only what was essential for life in nutrient-poor tropical waters. This strategy paid off spectacularly, but now, with oceans warming faster than ever before, Prochlorococcus is constrained by its genome. It can\u2019t retrieve stress response genes discarded long ago.<\/p>\n

\u201cTheir burnout temperature is much lower than we thought it was,\u201d Ribalet said. The previous models assumed that the cells would continue dividing at a rate that they can\u2019t sustain because they lack the cellular machinery to cope with heat stress.<\/p>\n

Possible Competitor: Synechococcus<\/p>\n

Prochlorococcus is one of two cyanobacteria that dominate tropical and subtropical waters. The other, Synechococcus, is larger, with a less streamlined genome. The researchers found that although Synechococcus can tolerate warmer water, it needs more nutrients to survive. Should Prochlorococcus numbers dwindle, Synechococcus could help fill the gap, but it isn\u2019t clear what the impact of this would be on the food chain.<\/p>\n

\u201cIf Synechococcus takes over, it\u2019s not a given that other organisms will be able to interact with it the same way they have interacted with Prochlorococcus for millions of years,\u201d Ribalet said.<\/p>\n

\"Sunset<\/a>Sunset aboard the Thomas G. Thompson, a University of Washington-operated research vessel equipped for ocean voyages. The instrument visible on the left is a water sampler that can collect from different depths, the SeaFlow flow cytometer was also aboard, but not pictured here. Credit: Kathy Newer\/University of Washington
\nClimate Models Predict Steep Decline<\/p>\n

Climate projections estimate ocean temperatures based on greenhouse gas emission trends. In this study, the researchers tested how Prochlorococcus might fare in moderate- and high-warming scenarios. In the tropics, modest warming could reduce Prochlorococcus productivity by 17%, but more advanced warming would decimate it by 51%. Globally, the moderate scenario produced a 10% decline while warmer forecasts reduced Prochlorococcus by 37%.<\/p>\n

\u201cTheir geographic range is going to expand toward the poles, to the north and south,\u201d Ribalet said. \u201cThey are not going to disappear, but their habitat will shift.\u201d That shift, he added, could have dramatic implications for subtropical and tropical ecosystems.<\/p>\n

Unanswered Questions Remain<\/p>\n

Still, the researchers acknowledge the limitations of their study. They couldn\u2019t study every cell or sample every body of water. Their measurements are based on pooled samples, which could mask the presence of a heat-tolerant strain.<\/p>\n

\u201cThis is the simplest explanation for the data that we have now,\u201d Ribalet said. \u201cIf new evidence of heat-tolerant strains emerges, we\u2019d welcome that discovery. It would offer hope for these critical organisms.\u201d<\/p>\n

Reference: \u201cFuture ocean warming may cause large reductions in Prochlorococcus biomass and productivity\u201d by Fran\u00e7ois Ribalet, Stephanie Dutkiewicz, Erwan Monier and E. Virginia Armbrust, 8 September 2025, Nature Microbiology.
DOI: 10.1038\/s41564-025-02106-4<\/a><\/p>\n

Co-authors include E. Virginia Armbrust, a UW professor of oceanography; Stephanie Dutkiewicz, a senior research scientist in the Center for Sustainability Science and Strategy at MIT; and Erwan Monier, co-director of the Climate Adaptation Research Center and an associate professor in the Department of Land, Air and Water Resources at UC Davis.<\/p>\n

This research was funded by the Simons Foundation and other government, foundation, and industry funders of the MIT Center for Sustainability Science and Strategy.<\/p>\n

Never miss a breakthrough: Join the SciTechDaily newsletter.<\/a><\/b><\/p>\n","protected":false},"excerpt":{"rendered":"The lines on the map are cruise tracks, overlaying temperature. The water in yellow areas hovers around 86…\n","protected":false},"author":2,"featured_media":60381,"comment_status":"","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[77],"tags":[442,18,4799,19,17,7019,10926,14999,133,43196],"class_list":{"0":"post-60380","1":"post","2":"type-post","3":"status-publish","4":"format-standard","5":"has-post-thumbnail","7":"category-science","8":"tag-climate-change","9":"tag-eire","10":"tag-global-warming","11":"tag-ie","12":"tag-ireland","13":"tag-marine-biology","14":"tag-microbiology","15":"tag-oceanography","16":"tag-science","17":"tag-university-of-washington"},"share_on_mastodon":{"url":"","error":""},"_links":{"self":[{"href":"https:\/\/www.europesays.com\/ie\/wp-json\/wp\/v2\/posts\/60380","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.europesays.com\/ie\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.europesays.com\/ie\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.europesays.com\/ie\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/www.europesays.com\/ie\/wp-json\/wp\/v2\/comments?post=60380"}],"version-history":[{"count":0,"href":"https:\/\/www.europesays.com\/ie\/wp-json\/wp\/v2\/posts\/60380\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.europesays.com\/ie\/wp-json\/wp\/v2\/media\/60381"}],"wp:attachment":[{"href":"https:\/\/www.europesays.com\/ie\/wp-json\/wp\/v2\/media?parent=60380"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.europesays.com\/ie\/wp-json\/wp\/v2\/categories?post=60380"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.europesays.com\/ie\/wp-json\/wp\/v2\/tags?post=60380"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}