Sargassum seaweed: The nightmare of tourists heading on a Caribbean holiday

Holidays are for having the time of your life and the Caribbean is a true paradise! Imagine you have dreamt of a white sand beach and turquoise waters for ages but when you finally get there, you’re facing a nightmare on that beach. The air smells of dead fish and the only thing you can see is brown stuff floating in the ocean. What is this? You are looking at tons of sargassum seaweed stretching along the coastline and quite far out ahead. It is literally impossible to enter the water…

In the past years, a fenomena has hit the Caribbean coasts. It has affected both the economy and the ecology from Mexico to Panama. Sargassum, sargasso, seaweed, rockweed or gulfweed are the different names given to this invasive macroalgae. It covers the sea front, keeps away tourists from a swim and takes numerous victims among the marine life.

 

What is sargassum?

Sargassum is an abundant seaweed in the ocean. There are different species and floating rafts of sargassum can stretch for miles across the ocean. This buoyant habitat provides food, refuge, and breeding grounds for an array of critters such as fish, sea turtles, marine birds, crabs, shrimps, and many more. Some animals, like the sargassum fish (in the frogfish family), live their whole lives only in this habitat. Sargassum serves as a primary nursery area for a variety of commercially important fish such as mahi mahi, jacks, and amberjacks.

When sargassum loses its buoyancy, it sinks to the seafloor. Thus it provides energy in the form of carbon to fish and invertebrates in the deep sea. 

Because of its ecological importance, sargassum has been designated as essential fish habitat. 

 

What does the seaweed look like?

Many leafy appendages, branches and round berry-like structures make up the sargassum. These “berries” are gas-filled structures, called pneumatocysts, which are filled mostly with oxygen. Pneumatocysts add buoyancy to the sargassum and allow it to float on the surface.

 

Which parts of the Caribbean are invaded by sargassum?

The sargassum seaweed can be found on the Caribbean coastlines of Mexico, Honduras, Nicaragua, the Dominican Republic, Jamaica, Trinidad and Tobago, Haiti, Cuba, Panama, Guadeloupe (a French overseas region), Belize, Guyana and Guatemala.

 

Riviera Maya seaweed map in Mexico

This map is from the Facebook page of the “red de Monitoreo del Sargazo Cancun” published on July 28th 2019.

 

Where is there no sargassum seaweed on the beach?

Even though sargassum algae has invaded the beaches and coastlines of the Riviera Maya from Cancun to Tulum in Mexico, there is a place where you don’t find it. The west coast of Cozumel island is absolutely preserved. If you are planning a trip to the Caribbean, this is the one and only place where you will definitely not find sargassum. This marine protected area also hosts some of the best coral reefs in Mexico so apart from enjoying clean white sand beaches, you can practise many watersports, snorkeling and scuba diving at the best dive spots in Cozumel.

 

Where does the name Sargassum come from?

Sargassum was named by the Portuguese sailors who found it in the Sargasso Sea, east of North America. It was apparently the name they gave to the wooly rock rose that grew in their water wells that they called sargaço. This huge amount of seaweed is the only sea on the planet that is not bordered by land. The ocean currents that sweep around it and contain it define its frontiers. This means that the floating sea of sargassum does not have a permanent location.

 

What species of sargassum dominates the Caribbean Sea?

The Sargasso Sea seems to be largely composed of two species: Sargassum natans and Sargassum fluitans. They probably originate in the Caribbean, but the floating masses seem to propagate themselves by fragmentation. Seaweed cells are totipotent and any fragment of a brown algae can regenerate an entirely functioning plant. Those two species are the ones that cover the coastlines of the Caribbean Sea.

 

What causes sargassum and brings it to so many of the coasts?

Several factors could explain the proliferation of sargassum in the Caribbean in recent years. These include the rise of water temperature and the change of sea currents due to climate change. Also, nutriments from agricultural fertilizers and wastewater from the cities that end up in the sea could make the algae flourish.

The clumps of floating algae are often accumulated by the strong winds and wave action associated with the Gulf Stream. Hurricanes in that region of the world could also be a factor of spreading the seaweed.

 

How bad are the consequences of sargassum seaweed being washed off at shore?

Health authorities warn the population in contact with sargassum of the serious threat it has to human health. As sargassum arrives on the shores and begins to decompose, its color goes from yellow to red to brown to black, releasing acrid noxious gases, such as hydrogen sulphide and ammonia after 48 hours, which produce a malodour. 

The effects on humans of exposure to high concentrations of hydrogen sulphide can lead to potentially fatal hypoxic pulmonary, neurological, and cardiovascular lesions.  

Moreover sargassum near the shorelines across the Caribbean has already caused the death of fish, octopuses and sharks. 

The masses of seaweed restrict turtles from reaching their spawning sites. On top of that, their offspring now find one more obstacle on their way to the open sea.

Another ecologic disaster caused by the huge amount of sargassum that has reached these coasts is the decrease of oxygen in the water. This has resulted in the death of fish and the proliferation of bacteria.

 

What actions have been taken?

Scientists and R&D departments are in the early stages of converting the sargassum into usable compost, concrete blocks and bio-fertilizers and a bio-fuel that can generate electricity.

For the time being, authorities have installed floating net barriers in touristic areas to keep the algae away from the beaches.

 

About the author

Nicolas Cesaroni has adopted scuba diving as his way of life since his first dive in 2010 in South-East Asia. A few months later he was a scuba Instructor, and a new life began. He decided to live his passion on a daily basis and explore as many tropical destinations as possible. He’s been diving and teaching scuba ever since in the best destinations in the world from Indonesia to Mexico by way of Thailand, Sri Lanka, Maldives, Seychelles, Egypt, Tanzania, South Africa, Greece, Germany, France, The Bahamas, Belize, Honduras, Costa Rica, and Panama.

He has become an avid underwater photographer over the years and his favourite critters are the tiny ones. You can find his stunning shots on his Instagram account @ocean.nico. In 2019, he took time out and co-founded the Dive into Life blog. The following year, having missed being underwater every day and living on remote islands, he was back in teaching status in the Maldives, where he is currently working.

When he is not underwater or editing pictures, Nico is a mixologist and he loves cooking.