Already under attack from erosion and rising seas, South Florida beaches are facing a new crisis: the invasion of Sargassum seaweed.
Washing ashore in increasingly alarming amounts, Sargassum is coating coastlines over much of the state.
“We’ve seen hurricanes, rainstorms, king tides on South Beach, but this is a new one,” Florida International University professor Dr. Stephen Leatherman said. And he should know – he’s nicknamed Dr. Beach for his more than 40 years studying one of our most treasured natural resources.
His concern is shared.
“Sargassum is a good thing,” Dr. Brian Lapointe of Florida Atlantic University's Harbor Branch Oceanographic Insitute said. “It’s fish factory when it’s offshore, but when it comes ashore in excessive amounts, it becomes problematic.”
Lapointe has been monitoring this floating seaweed for decades, using satellites to track the 5,500-mile-long Great Atlantic Sargassum Belt.
Stretching from the Gulf of Mexico to West Africa, the Belt is home to more than 20 million tons of Sargassum in this recent bloom.
“Since 2011, we have seen this ramping up, up and away," Lapointe said.
Sargassum in the open water or even on our beaches is nothing new. The excessive amount of it is. It’s choking our shores and causing an awful stench as it rots in the sand.
“People don’t like it. It stinks. It attracts flies and it smells like rotten eggs and it’s very unpleasant,” Leatherman said. “So I can say this, it’s going to really cut down tourism.”
That is an alarm bell to South Florida’s economy. The beaches are one of our economic engines.
“We’ve already seen this problem in the Caribbean where some islands are just covered with it," Leatherman added.
So much so, that boats couldn’t escape port. Swimmers couldn’t get to the water. Turtles couldn’t get onshore to lay eggs. Many hatchlings lucky enough to be born couldn’t reach the water to begin their journey.
Like many of the environmental destabilization events we are seeing, this is almost completely man-made. The source feeding the bloom is thousands of miles away.
“We have all heard about our carbon footprint – the CO2 and its relationship to climate change,” Lapointe said. “What you don’t hear so much about is the human nitrogen footprint.”
That footprint is leaving a giant-size mark on the Amazon Forest. Deforestation for cow pastures and crop farming continues at an alarming rate – 1-and-a-half soccer fields per minute.
To generate crops, farmers are using heavy amounts of fertilizer rich in the nutrient of nitrogen. Runoff from these lands reach the Amazon River and out into the Atlantic Ocean. As nitrogen fertilizes crops on land, so it does to seaweed in the ocean.
The carbon footprint of a changing climate is making the nitrogen footprint even worse.
“There are other aspects of climate change that are clearly playing a driving role in feeding the sargassum bloom and that is extreme rain events,” Lapointe describes. "They have been seeing extensive flooding since 2009.”
The extreme rains mean extreme amounts of runoff, turbo-charging the Sargassum bloom. The massive stretch of it floats north along the currents, bringing it to our doorstep.
“And the other thing, of course, is the Earth has warmed up,” Leatherman adds. “The seas have warmed up. And the warmer the water, the better the seaweed grows.”
The impact is both an economic one and an environmental one. Tourism could take a hit. So could the ocean ecosystem.
“It consumes oxygen and creates dead zones, which is not good,” Lapointe explains. “We lose all those marine habitats along the coastline that normally are a nursery ground for our fisheries. You get toxic hydrogen sulfide fumes being emitted from the water or the beach. It causes fish kills, a die-off of seagrasses and corals along the beaches.”
The hydrogen sulfide is what gives the Sargassum that rotten-egg smell.
Usually, normal amounts of the seaweed are plowed under the sand in the mornings by city and county beach crews. That’s just not possible now because of the excess.
“Miami-Dade County is searching for solutions. They can’t possibly get it underneath the sand,” Leatherman said.
Other actions will be costly.
“Miami Beach calculates it could cost as much as $45 million a year just to clean this seaweed off. That’s a big expense we haven’t seen in the past," Leatherman added.
Constant beach cleaning isn’t ideal and may not be sustainable.
Intercepting the Sargassum offshore before it reaches our beaches may not be either.
Lapointe said because of Sargassum is a hub of biodiversity that serves as a habitat for numerous species, the seaweed species is protected by law at sea.