Thinking of a Florida beach vacation? Think again, unless you like sargassum seaweed

A colossal seaweed bloom, predicted to grow to record-breaking proportions before reaching its peak in June, is currently affecting Florida beaches sporadically, depending on the direction of the wind. 

From Montego to Miami, the influx of sargassum algae is leaving unpleasant, brown, smelly carpets on what was once prime tourist sand. Researchers have observed the highest levels of sargassum this early in the year.

Managing this overwhelming seaweed accumulation is becoming increasingly challenging as more is learned about it, prompting some entrepreneurs to reconsider the removal of sargassum altogether.

What is sargassum seaweed?

Sargassum is a buoyant, rootless algae that forms in islands and drifts across the ocean. Patches of sargassum have been spotted in the Atlantic Ocean for centuries, but a 5,000-mile-long belt of seaweed has been circulating annually between the Gulf of Mexico and the mid-Atlantic since 2011. 

The density of clusters within this belt continues to increase, possibly because modern agriculture techniques are causing more nutrients to flow downstream and into the ocean.

In April, sargassum levels in the Caribbean Sea reached a new record, with the overall belt expanding to an estimated 13 million tons, according to a bulletin from the University of South Florida’s Optical Oceanography lab. 

The peak bloom season is still days away, with the climax expected to occur in June or July. “If the past is precedent, the bloom size could double in the next month,” said Brian Barnes, a researcher at USF’s College of Marine Science, in an interview with the NSF.

Predicting the impact of this massive bloom on beaches is difficult, particularly in the eastern Atlantic where persistent clouds are obscuring the satellite views that Barnes and his team rely on. However, sargassum beachings are already on the rise, with the southern regions of Hispaniola, Jamaica, and Puerto Rico appearing to be the most affected areas.

Once it hits the beaches, sargassum seaweed cannot be ignored

Once sargassum reaches the shore, it not only becomes an unsightly obstacle for swimmers but also emits a foul odor. Within 24 hours of hitting the shore, the seaweed starts to decay, releasing hydrogen sulfide and producing a smell akin to rotten eggs. There is evidence to suggest that these gases can lead to nausea, headaches, and aggravation of respiratory issues. 

During an eight-month period of intense beach buildup in 2018, doctors on the islands of Guadeloupe and Martinique reported over 11,000 cases of “acute sargassum toxicity,” according to Reuters.

Moreover, the presence of sargassum can have significant economic repercussions. In the Florida city of Key West, for example, Public Information Officer Alyson Crean explains that the largest public beach stretches only about half a mile in length, and Key West is not primarily considered a beach town. 

However, a 2020 analysis discovered that 1 in 10 tourists would either cancel or reschedule their trip to Key West if they were aware of sargassum’s presence. Consequently, a bad sargassum year could result in a $20 million loss for the $2.4 billion Key West tourism industry and lead to the elimination of approximately 300 jobs, according to the report.

The life cycle of sargassum seaweed

Sargassum’s natural growing season typically occurs during the spring months, with the total amount of seaweed expected to increase in May and peak in June. The growth of sargassum over the past few months has not been surprising, but researchers were caught off guard in January when the amount of sargassum in the Atlantic doubled for the second consecutive month. 

An upwelling of cool water bringing nutrients from the ocean floor to feed the sargassum may be responsible for this winter growth, but as of now, that remains speculative.

Last month, total measurements of the Great Atlantic Sargassum Belt, which extends from the coast of Africa to the Gulf of Mexico, were challenging to obtain due to cloud cover. In July 2022, the sargassum reached a record-breaking peak of 22 million tons, and 2023 could potentially surpass this amount, making it another major sargassum year.

Is sargassum seaweed harmful to humans and wildlife?

Sargassum seaweed can be both beneficial and harmful to humans and wildlife, depending on the circumstances.

For humans:

Recreational issues

Large amounts of sargassum on beaches can make swimming and other water activities unpleasant. The decaying seaweed can produce an offensive odor and cause skin irritation for some swimmers.

Health concerns

As sargassum decomposes, it releases hydrogen sulfide gas, which can cause nausea, headaches, or aggravate respiratory issues, especially for people with asthma or other respiratory conditions.

Heavy metal contamination

Some studies have found that decomposing sargassum can release heavy metals like arsenic into the environment, posing potential risks to human health, especially if the seaweed is used as fertilizer or livestock feed.

For wildlife: 

Habitat and food source

Sargassum provides a crucial habitat and food source for various marine species, including fish, crustaceans, and sea turtles. Migratory birds also rely on sargassum during their long journeys across oceans.

Obstruction for marine life

Excessive sargassum can choke waterways, clog boat propellers, and create barriers for sea turtle hatchlings trying to reach the ocean. In extreme cases, it can smother coral reefs, seagrass beds, and other sensitive marine habitats, impacting their health and biodiversity.

Eutrophication

Decomposing sargassum releases nutrients that can contribute to eutrophication, causing algal blooms and leading to oxygen depletion in the water. This can harm marine life by creating “dead zones” where oxygen levels are too low to support most aquatic organisms.

In summary, sargassum seaweed has both positive and negative effects on humans and wildlife. While it plays a crucial role in supporting marine ecosystems, excessive growth and accumulation can lead to several challenges. Managing sargassum blooms and mitigating their negative impacts is essential for maintaining a healthy balance between its benefits and potential harm.

How scientists are attacking the problem

Removing sargassum seaweed from the shores is just one part of the challenge; disposing of it is another issue altogether. Alyson Crean, Key West’s Public Information Officer, said that the company contracted by Key West donates sargassum to farmers for use as fertilizer. In Mexico, the seaweed is trucked inland to decompose in the jungle, according to National Geographic.

However, processing or decomposing sargassum may become more expensive as the field of sargassum study expands. Researcher Brian Lapointe told NPR last month that new research indicates decomposing sargassum might release heavy metals into the surrounding environment. 

A study examining sargassum along Mexican beaches found that 86% of samples contained arsenic levels higher than the United Nations’ limit for livestock feed – a repurposing idea explored earlier.

Despite these challenges, companies are experimenting with creative solutions, such as transforming sargassum into biofuel, construction material, or even medicinal products. One promising idea involves a two-fold approach: sinking sargassum to prevent carbon release, thus combating climate change.

UK-based startup Seaweed Generation is developing an autonomous robot to intercept sargassum patches close to shore, drag them back out to the open ocean, and force them to sink to a depth of 1,000 meters, effectively trapping carbon in the ocean. The company plans to deploy two AlgaRays from a support vessel. 

Traveling through the water at around 3 knots, a fully loaded AlgaRay will descend to a depth beyond 135 meters, releasing negatively buoyant sargassum. The rear AlgaRay then takes over the collection, with the process captured on video and recorded with blockchain technology.

Seaweed Generation CEO Paddy Estridge explains, “Carbon removal with seaweed could really scale, and we can do that with cultivation, but there are questions that need to be answered first. Sargassum gives us an amazing opportunity to solve a known problem, whilst conducting the monitoring, reporting, and verification that we know carbon removal needs.” Seaweed Generation raised funding through AeraVC and Graph Ventures.

Until AlgaRay operates at full capacity, the best option for individuals concerned about sargassum might be patience or avoidance. Researcher Brian Barnes, who tracks sargassum using satellite images, advises against canceling beach vacations even if local governments aren’t performing daily cleanups. 

“The effects are very, very local,” said Barnes. “You’ll see a huge, unbelievable amount of sargassum in one little bay, but if you look past that into the next bay, there’s absolutely no sargassum.” 

However, for those still concerned, Barnes suggests monitoring sargassum blooms closely as they approach the shore.

What is the environmental impact of sargassum seaweed? 

Sargassum seaweed has both positive and negative environmental impacts.

Positive impacts include: 

Providing habitat

Sargassum serves as a habitat for various marine species, including fish, crustaceans, and sea turtles. It offers food, shelter, and breeding grounds for these organisms, which contributes to marine biodiversity.

Supporting migratory birds

Migratory birds often rely on sargassum for food and rest during their long journeys across oceans.

Carbon sequestration

Sargassum can absorb and store carbon dioxide, helping to mitigate the effects of climate change.

Negative impacts include: 

Beach fouling

Large amounts of sargassum washing ashore can be unsightly and create an unpleasant smell as it decomposes, potentially affecting tourism and local economies.

Health concerns

Decomposing sargassum releases hydrogen sulfide gas, which can cause nausea, headaches, or aggravate respiratory issues in humans.

Eutrophication

When sargassum decomposes, it releases nutrients that can contribute to eutrophication, causing algal blooms and leading to oxygen depletion in the water, harming marine life.

Heavy metal leaching

Some studies have found that decomposing sargassum can release heavy metals like arsenic into the environment, posing potential risks to human and environmental health.

Obstruction for marine life

Excessive sargassum can choke waterways, clog boat propellers, and create barriers for sea turtle hatchlings trying to reach the ocean.

Overall, while sargassum plays a crucial role in supporting marine ecosystems, its excessive growth and accumulation can lead to several environmental challenges. 

These negative impacts are often a result of human activities, such as nutrient pollution from agricultural runoff, which can contribute to the rapid growth of sargassum in the oceans.

As the sargassum seaweed bloom continues to impact coastal areas, it presents challenges to local economies, tourism, and marine ecosystems. Identifying the cause of its rapid growth and developing strategies to manage its presence remain critical tasks for researchers and coastal communities alike.

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