Ocean Regime Shift: seaweed Blooms Surge,Driven by Climate Change and Pollution
A dramatic increase in seaweed blooms across the globe signals a potential regime shift in ocean ecosystems,fueled by rising temperatures and agricultural runoff. new research reveals a staggering 13.4% annual expansion of these blooms over the past two decades, raising concerns about profound impacts on marine life, climate patterns, and ocean health.
Unprecedented Growth in Seaweed Blooms
Researchers at the University of South Florida have documented an unprecedented surge in macroalgae – commonly known as seaweed – across the tropical Atlantic and western Pacific oceans. The most notable acceleration in growth occurred after 2008, indicating a clear turning point in ocean conditions.
“Before 2008, there were no major blooms of macroalgae reported except for sargassum in the Sargasso Sea,” explained a senior researcher involved in the study. “On a global scale, we appear to be witnessing a regime shift from a macroalgae-poor ocean to an macroalgae-rich ocean.”
Visible From Space: The Scale of the Problem
The scale of these blooms is now so vast that they are visible from space. The Great Atlantic Sargassum Belt, stretching from the Gulf of Mexico to the mouth of the Congo River, serves as a stark example. Other significant blooms have been observed around the Chatham Islands off New Zealand – captured by NASA imagery this month – and in the form of “red tides” off the coast of Florida,which state authorities have been monitoring.
AI-Powered Analysis Reveals Global Trend
The research team employed artificial intelligence to analyse 1.2 million satellite images of the world’s oceans, spanning the period between 2003 and 2022. A deep-learning model was used to identify and track the proliferation of floating algae, a process that required several months of intensive computation. This analysis provides the frist comprehensive global picture of algae blooms in the world’s oceans.
While both macroalgae and microalgae (such as phytoplankton) have increased, the growth rate of seaweed is significantly higher. Microalgae blooms increased by a more modest 1% annually during the same period.
Warming Waters and Nutrient Runoff: A Risky Combination
The researchers attribute the dramatic increase in seaweed blooms to a combination of factors, primarily global ocean warming and increased nutrient pollution from agricultural runoff and other sources. They identified key tipping points in 2008,2011,and 2012,suggesting a cascading effect as ocean conditions changed.
“What is noteworthy is that most increases in both floating macroalgae and microalgae scums occurred in the recent decade, in line with the accelerated global ocean warming as 2010,” the authors wrote in their published findings.
Implications for Ocean Ecosystems and Climate
The shift towards macroalgae-dominated oceans has potentially far-reaching consequences. Seaweed blooms can darken the waters below,altering marine ecology and geochemistry. This change in light availability could disrupt the food chain and impact marine biodiversity.
Furthermore, the researchers suggest that this regime shift could accelerate climate breakdown by affecting radiative forcing in the atmosphere, carbon sequestration, and ocean biogeochemistry. The increased presence of macroalgae could alter the ocean’s ability to absorb carbon dioxide, potentially exacerbating climate change.
“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 concluded.
The findings were published in Nature Communications.
