Scientists have warned of a potential “regime shift” in the oceans, as the rapid growth of huge beds of seaweed appears to be driven by global warming and over-enrichment of waters from agricultural runoff and other pollutants.
Over the past two decades, seagrass blooms have expanded by a staggering 13.4% per year in the tropical Atlantic and western Pacific, with the most dramatic increases occurring after 2008, according to researchers at the University of South Florida.
In new research, they say this shift could darken the water below, change its environment and geochemistry, and may even accelerate climate breakdown.
“Before 2008, there were no major macroalgae blooms [seaweed] “They have been reported with the exception of Sargassum in the Sargasso Sea,” said Quanmin Hu, a professor of oceanography at the University of South Florida’s College of Marine Sciences and lead author of the paper.
“On a global scale, we appear to be seeing a regime shift from a macroalgae-poor ocean to a macroalgae-rich ocean.”
He and his colleagues conducted the research in response to reports of expanding seaweed blooms in the Atlantic and Pacific Oceans.
The most famous example is the Great Atlantic Sargassum Belt, visible from space, extending from the Gulf of Mexico to the mouth of the Congo. Other flowers include a ring around the Chatham Islands off New Zealand, Captured by NASA This month, or the “red tide” that appeared off the coast of Floridawhich has been monitored By the state.
Scientists used artificial intelligence to scan 1.2 million satellite images of the oceans taken between 2003 and 2022. A deep learning model was used to detect signals from the floating algae – a process that took several months.
The team, which says their study provides the first global picture of algae floating in the world’s oceans, found that seaweed blooms increased in area by 13.4% per year during the period examined. Microalgal blooms, such as phytoplankton, also increased, but by a relatively more modest 1% per year.
“What is noteworthy is that most of the increases in both free-floating macroalgae and microalgae occurred in the last decade, consistent with accelerating global ocean warming since 2010,” the researchers wrote. They identified turning points in 2008, 2011 and 2012 for three types of seaweed in different oceans.
However, while seaweeds such as sargassum have flourished in some areas, phytoplankton have not shown similar responses to the changing environment, suggesting that their growth may be more sensitive to changes in temperature and climate changes. Eutrophication.
“If this is the case, we believe that a regime shift in oceanic conditions has already occurred favoring macroalgae, which will have profound effects on atmospheric radiative forcing and light availability in the ocean, as well as on carbon sequestration, ocean biogeochemistry and upper ocean stability,” the researchers wrote.
The results are published in the journal Nature Communications.