A massive bloom of Sargassum seaweed, estimated to be the largest ever recorded, is currently circling around the Gulf of Mexico
04-09-2023

Stunning photos show Sargassum seaweed bloom nearing Florida beaches

A massive bloom of Sargassum seaweed, estimated to be the largest ever recorded, is currently circling around the Gulf of Mexico and could soon wash up on the US east coast near Florida. This floating mat of algae is so large that it is visible from space. 

Sargassum is a rootless and buoyant algae that forms large floating mats on the ocean surface. It is an important habitat for marine species, providing food, refuge, and breeding grounds.

What is Sargassum?

First written about by Christopher Columbus in 1492, Sargassum is found in the Sargasso Sea and other parts of the Atlantic Ocean. Like other floating marine vegetation, Sargassum absorbs atmospheric carbon dioxide through photosynthesis and converts it into organic carbon, which makes it an important tool in mitigating the effects of greenhouse gases.

However, when Sargassum collects along coastlines, it can emit toxins like hydrogen sulphide, which produces a pungent smell. These toxins can cause headaches, eye irritation, and upset stomachs, depending on the quantity. Mounds of algae on beaches can harm marine ecosystems and disrupt recreation and fishing, costing communities millions.

History of Sargassum Blooms

Scientists have been tracking Sargassum blooms since 2011, but this year’s bloom is estimated to be the largest ever, collectively spanning more than 8800 km from the shores of Africa to the Gulf of Mexico and weighing 10 million tonnes. 

According to Chuanmin Hu, a professor of oceanography at the University of South Florida, the size of this bloom is due to the convergence of multiple factors, including changes in ocean currents, the amount of nutrients in the water, and the winds.

In an interview with CNN, Professor Hu said: “It’s a combination of things we’ve never seen before.” He went on to explain that the Gulf of Mexico is the final destination for many of the world’s rivers, which carry nutrients that can fuel the growth of Sargassum. The increase in ocean temperature due to climate change is also a factor, as Sargassum thrives in warm water.

Sargassum seaweed extent seen from space
Sargassum seaweed extent seen from space

While Sargassum plays an important role in marine ecosystems, the massive amount currently floating in the Gulf of Mexico poses a potential threat to coastal communities. As the bloom moves closer to the US coast of Florida, officials are monitoring the situation and preparing to respond if necessary. 

According to Florida’s Fish and Wildlife Conservation Commission: “The severity of the impacts of the Sargassum landing events on Florida’s coastline depends on many factors, including the timing, location, quantity, and duration of the event.”

“We need to prepare for the worst-case scenario,” said Professor Hu. While it’s impossible to predict exactly when or where the Sargassum will make landfall, experts are keeping a close eye on the situation and working to better understand this unique phenomenon.

Sargassum Seaweed Belt Seen from Space

The European Space Agency (ESA) is collaborating with CLS-NovaBlue Environment to monitor floating Sargassum using data from Earth observation satellites as part of ESA’s Earth Observation Science for Society initiative. Sargassum is a type of seaweed that is found in the Sargasso Sea, which is located in the western North Atlantic Ocean.

To better understand the extent and evolution of the Sargassum belt stretching across the Atlantic Ocean, multispectral satellite measurements from Sentinel-2 at 10m resolution have been used to capture the density and size of Sargassum levels since 2011. This is complemented by radar altimeter measurements from Sentinel-3 and Sentinel-6 satellites that provide access to geostrophic ocean currents.

Great Atlantic Sargassum Belt
Great Atlantic Sargassum Belt

“These Copernicus Sentinel-2 images show the Sargassum around 45 km off the west coast of Guadeloupe. The image on the left is a true-color image while the one on the right has been processed using the near-infrared channel to highlight the Sargassum in bright red,” says ESA.

The Ocean Virtual Laboratory, which allows oceanographers to discover the world’s oceans, has also been monitoring the Sargassum. The virtual lab uses more than 350 datasets, Copernicus Sentinel data, in situ measurements, and numerical model outputs to provide an unprecedented view of our oceans and improve scientific understanding of ocean and coastal processes leading to the Sargassum.

How Sargassum is Monitored

The Sargassum mats, which are being monitored, could soon threaten beaches along the Florida Keys, Mexico’s Yucatán Peninsula, and the eastern Caribbean. The trajectory of ocean currents that are leading the Sargassum westward can be monitored using satellite data, providing valuable insight into the extent of the threat.

“Since 2011, a change in the density and in size of Sargassum levels has been seen which can be monitored from space in different ways,” says ESA. With the help of satellite data, oceanographers are gaining a better understanding of ocean and coastal processes leading to the Sargassum and are able to provide an unprecedented view of our oceans.

As our planet continues to change, it is important to monitor and understand the impacts on our oceans. The collaboration between ESA and CLS-NovaBlue Environment is a great example of how satellite data can be used to monitor our planet and improve our understanding of the natural world.

Map showing the sargassum seaweed extent
Map showing the sargassum seaweed extent

More about Sargassum seaweed

Sargassum seaweed is a type of brown algae that has been causing concerns in recent years due to its increased occurrence in the Caribbean Sea, Gulf of Mexico, and the Atlantic Ocean. The seaweed forms large mats that can cover the surface of the water, affecting marine ecosystems, tourism, and fishing industries.

Sargassum is a naturally occurring seaweed that has been present in the Atlantic Ocean for thousands of years, forming the Sargasso Sea in the middle of the North Atlantic. However, in recent years, the seaweed has been growing excessively and drifting towards the Caribbean, causing problems for coastal communities and marine life.

Where is this Sargassum coming from?

The growth of Sargassum is thought to be linked to climate change, as warmer sea temperatures and changes in ocean currents have created the perfect conditions for its proliferation. The seaweed can also thrive in nutrient-rich waters, such as those polluted by agricultural runoff.

The excessive growth of Sargassum can have serious consequences for marine life, as it can smother coral reefs and seagrass beds, and affect the distribution and abundance of fish and other marine organisms. The seaweed can also cause beach closures and harm the tourism industry, as the smell and appearance of the seaweed can deter visitors.

Efforts are being made to address the Sargassum problem, including the use of specialized boats to collect the seaweed and its conversion into fertilizer and other products. However, these solutions are still in their early stages and face challenges such as cost-effectiveness and the scale of the problem.

Overall, Sargassum seaweed is a complex issue that requires a multi-disciplinary approach to address. Continued research into the causes and effects of Sargassum growth, as well as innovative solutions for its management and utilization, will be crucial for ensuring the health and sustainability of marine ecosystems and coastal communities.

image Credit: ESA

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