In a startling revelation, scientists have warned of a potential “regime shift” in the world’s oceans, as vast blooms of seaweed continue to expand at an alarming rate. Over the past two decades, these macroalgae have been growing by an astonishing 13.4% per year in the tropical Atlantic and western Pacific, with the most dramatic increases occurring after 2008.
The research, led by Professor Chuanmin Hu of the University of South Florida’s College of Marine Science, paints a concerning picture of the state of our oceans. Using satellite imagery and advanced deep-learning models, the team scanned over 1.2 million images taken between 2003 and 2022, uncovering a dramatic rise in both floating macroalgae and microalgae.
“Before 2008, there were no major blooms of macroalgae reported except for sargassum in the Sargasso Sea,” explained Hu, the senior author of the study published in Nature Communications. “On a global scale, we appear to be witnessing a regime shift from a macroalgae-poor ocean to a macroalgae-rich ocean.”
The scientists identified critical tipping points in 2008, 2011, and 2012, marking the accelerated growth of different seaweed species across various ocean regions. The best-known example is the Great Atlantic Sargassum Belt, a vast expanse of floating sargassum that is visible from space, stretching from the Gulf of Mexico to the mouth of the Congo.
Worryingly, the researchers believe this shift in ocean conditions has already favoured the proliferation of macroalgae, which could have profound impacts on the planet. These include changes in radiative forcing in the atmosphere, light availability in the oceans, carbon sequestration, ocean biogeochemistry, and upper ocean stability.
“If this is the case, we believe that a regime shift in oceanographic conditions has already occurred to favour macroalgae, which will have profound impacts on radiative forcing in the atmosphere and light availability in the ocean, as well as on carbon sequestration, ocean biogeochemistry and upper ocean stability,” the researchers wrote.
The findings come as a stark warning, highlighting the urgent need to address the underlying drivers of this seaweed explosion, which the scientists link to global heating and excessive nutrient pollution from farming and other sources. As the world’s oceans continue to undergo dramatic transformations, the implications for marine life, climate, and human well-being cannot be overstated.
