The Sargassum Seaweed Problem

It constantly gets stuck on our fishing line. Once washed ashore it starts smelling like rotten eggs. It can irritate the skin when you swim or walk in it. It clogged up our toilet pump and simply impacts the beauty of sandy beaches and anchorages. It’s not only affecting us as sailors, but especially locals, marine life and tourism. Sargassum seaweed has become a real plague in the Caribbean that apparently worsens year by year. Locals are now finding ways to cope with the problem and they prepare for it, as they do for potential hurricanes. We wanted to better understand the situation…

Since we left port in Cabo Verde we have seen large fields of seaweed across the entire Atlantic making us wonder where it comes from, why it expands over such a large area, if the amount we see is usual, and if not, what the consequences are for the local environment. We mostly got frustrated when we had to pull in our fishing line many times a day when sargassum entangled on the bait and hooks. Often it got stuck on our propeller and slowed us down. We see the same type of seaweed everywhere on the Eastern Caribbean islands mostly in large fields floating in open water or washed ashore on beaches.

To answer the questions we had, we did some research and talked to locals and other cruisers about it. Here is what we have learned:

What is sargassum and where does it come from?

Coming from the equatorial water between Brazil and West Africa, sargassum is a stringy, brown type of seaweed that floats in large island-like masses at the surface of the ocean since thousands of years. The small gas filled bubbles keep the algae floating while the strings entangle and create an important habitat for different animals such as fish, turtles, birds, crabs, shrimp, etc. It mostly serves as protective environment for nesting and larvae while some species spend their whole life in this habitat. When the seaweed dies, it loses its buoyancy and sinks to the bottom of the ocean where it is thought to be an important energy source for deep sea fish and invertebrates. In the past smaller patches occasionally used to break off and were carried by currents into the Gulf of Mexico and Caribbean Sea. Since 2011, however, the amount of seaweed washed up ashore increased drastically and researchers began to investigate.

What causes the increase of sargassum?

The so called Great Atlantic Sargassum Belt, which we came across on our Atlantic passage, is stretching over 8,850km (5,500 miles) between the African and Caribbean coast and was estimated to weigh over 22 million tonnes in 2019. Research is still ongoing and exploring the true origin and impacts of the invasion. According to continued research the increased bloom of seaweed is potentially caused by a nutrient-rich upwelling and soil erosion from the western African coast combined with deforestation and fertilisers flowing from the Amazon into the ocean and ultimately related to rising sea temperatures as a result of climate change. Although floating sargassum patches offshore play an important role in marine ecology, the increased influx of sargassum in coastal areas not only causes implications for local fishermen, boats, and tourists, but also negatively impacts the local environment.

What are the consequences of increased sargassum influx?

Let’s start with the environmental impacts. The vast fields of seagrass trap marine life and choke coral reefs. The influx is causing an environmental issue. It disrupts the equilibrium of coastal ecosystems, negatively affects local marine life and by killing off the seagrasses that help keep sand in place, is causing beaches to erode more rapidly, which also destroys nesting areas for sea turtles.

The drop of fish populations worries local fisherfolk who in some areas are struggling to get in the water or, like us, have their boats, outboard propellers, nets and lines entangled in sargassum.

Moreover it repels tourists from visiting due to the disgusting smell sargassum produces when decaying and ugly sight on the otherwise so beautiful beaches. Many cruisers we have talked to chose to visit islands or anchorages that are less affected. Local authorities attempt to organize beach clean-ups, especially in popular tourist destinations, but the cost of collecting and disposing of sargassum is expensive and the sudden arrival of sargassum masses too unpredictable. While we were reading more about the issue, we came across some other more feasible and positive solutions that will help improve the situation.

What are the solutions to the problem?

To find a suitable solution to fight the problem we need to go back and look at the main causes of the sargassum spread in the Atlantic. Ultimately it all comes back to the arguably most important challenge humans are facing: climate change.

Changing weather patterns create wind, storms and currents that cause disturbances in liquid boundaries allowing sargassum to spread. Another starting point is to preserve and protect crucial natural environments like the Amazon or Congo region instead of exploiting nature by destroying major areas of rainforest for unsustainable agricultural and farming projects, especially pumping chemical fertilisers into the soil, which finally tip the balance of nature in rivers and oceans.

Meanwhile in the Caribbean it seems like every impacted country is coming up with their own solutions to deal with the sargassum plague. Some islands prevent sargassum to come onshore by installing floating nets or using boats to collect seaweed patches offshore. Some companies see sargassum even as a business opportunity and use it to produce organic fertiliser, biofuel, soap and other cosmetics, paper, building material or livestock fodder. As the subject is still not perfectly understood and researchers are further trying to understand the development and causes of the Great Atlantic Sargassum Belt, it is a challenge for local authorities to find and develop effective, long-term solutions.

Writing this we do not mean to create a false picture of the current state of Eastern Caribbean islands. Being directly exposed to seaweed as cruisers and having many questions about it, we wanted to share the insights we have gained about this topic. Many beaches and bays, windward and leeward facing, are not impacted as much by the seaweed influx as shown in the pictures. Most accumulations of sargassum in anchorages or on beaches are acceptable and do not significantly impact our activities and enjoying the lovely atmosphere of Caribbean beaches and coastlines. The smell of rotting sargassum is rarely blown exactly towards us or the boat and varies in intensity depending on the wind. We have not yet felt the need to leave any anchorage earlier than planned or not to do any activities due to sargassum. Even though it is a problem to be solved and has some negative impacts, also on cruisers, it should not keep anybody from visiting these beautiful destinations.

Online sources used amongst talking to locals and other cruisers:

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