Algae blooms are expanding across the world's oceans.
The first global study of floating algae was recently released by researchers at the University of South Florida College of Marine Science and the National Oceanic and Atmospheric Administration.
The scientists fed 1.2 million satellite images from NASA and NOAA taken between 2003 and 2022 into an artificial intelligence program to catalogue the visible amount of macroalgae.
They focused on 13 zones and five types of algae.
Chuanmin Hu, a professor of oceanography at USF, coauthored the study with Lin Qi of NOAA.
They observed blooms beginning to expand in the years surrounding 2010.
"They became larger and larger. And this trend has not stopped," Hu said.
They're still growing even now.
"A warmer ocean would favor more growth," he said.
Rising temperatures, increasing nutrients, and changing currents could all be factors in the algae expansion.
Hu said these blooms are becoming the new normal, which can be a positive for marine life in open water as it can provide critical habitat serving as a nursery for juvenile species.
But it can be a negative for coastal communities when it reaches them as a decaying biomass.
"Which may cause problems to beaches, to tourism and to fisheries, to [the] economy," he said.
The findings were peer-reviewed and published in the scientific journal Nature Communications.
Hu credits all the federal satellite initiatives over the years with making this study possible.
"There are a lot of heroes behind the curtain. We just don't see them. Otherwise, this work is impossible without their support," he said.
Hu added, there's still more to learn … like how to predict, monitor and track future blooms.
"Although we have a general understanding, in principle, why we have seen the expansion … there are regional-dependent reasons," he said.
"How exactly a certain plant makes use of different nutrient species: nitrogen, phosphorus, iron. And under what conditions the usage of nutrient is more effective than in other conditions."
Hu was also part of a recently published analysis on the decline of the Sargasso Sea, which has historically been a large algae mat off the eastern coast of North America utilized by marine life, including endangered sea turtles.
That study described how warming waters could also decrease algae.
"Temperature is a double-sided sword," Hu said.
ALSO READ: Warming waters could be contributing to the decline of the Sargasso Sea and its Gulf supply
The northern Gulf has previously generated and fed sargassum algae to the Sargasso Sea, but the higher temps have made the algae weaker for its journey.
So now there's only about 10% of the Sargasso Sea left prior to what was observed in 2015.
At the same time the Great Atlantic Sargassum Belt blossomed about 600 miles south in the tropical Atlantic, becoming the dominant area for that algae.
"Within the preferred temperature range, a warmer ocean would favor the growth. What about outside that range? The warmer, the worse," Hu said.
"If the baseline temperature is already above that range, a warmer ocean would decrease macroalgae, and that's what we think happened in the Gulf of Mexico and the North Sargasso Sea."
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