Stinking seaweed blooms: Turning environmental risk into opportunity

As Atlantic shores prepare for their annual onslaught of strong-smelling seaweed, scientists in a University of Southampton-led project are sharing their research on how affected communities can benefit from this putrid problem – by composting it.

The team has also developed an early warning system so that affected communities can prepare.

Large populations of sargassum seaweeds wreak seasonal havoc on coasts across the tropical Atlantic Ocean. Millions of tons of sargassum — and increasing annually — wash up on beaches from Mexico to Africa, threatening fishing, tourism and ecosystems, including turtles that can’t get to the beaches to lay their eggs.

Until 2011, Sargassum was contained in the Sargasso Sea, off the coast of Bermuda. Its spread south to warmer waters where it thrives was initially driven by an unusual weather event, but is now being pushed across the equatorial Atlantic by winds, currents, and changes in the pattern of the Atlantic meridian (the way the ocean moves). Huge clumps of seaweed can be seen from space, and 2023 is expected to be another very dangerous year.

Research project led by Southampton Sartrak (which has collaborated with the University of York, the University of Ghana, and the University of the West Indies in Barbados and Jamaica) has found sustainable uses for seaweed. These include fertilizer to support mangrove regrowth and to grow peppers and tomatoes.

The project team has also created resources for school teachers in Ghana to support them in teaching Sargassum identification and its uses, and has established an early warning system for Jamaica, which it is hoped will be rolled out to West Africa. The system combines geospatial data with socioeconomic data to provide advice on when and where to wash sargassum, enabling communities to prepare for cleanups and manage their impact.

Participating academics are meeting in Southampton this week to present their findings to peers and policymakers.

Project leader Emma Tompkins, professor of geography, environment and development at the University of Southampton, said: “When sargassum washes up on the beach, it can accumulate meters high and can be destructive. It causes breathing difficulties. It affects fishermen’s ability to catch fish, it affects tourism, and it’s a problem for ecosystems, especially for turtles that go to lay their eggs on the beaches in the summer when the sargassum is at its worst.”

The project team created methods for use by the poorest people affected by Sargassum.

Professor Tompkins said: “Rather than collecting on an industrial scale, we looked at how sargassum could be used by coastal communities and small-scale farmers. Successful uses include supporting mangrove growth, and as an organic fertilizer for growing peppers and tomatoes which are important crops for poor communities.”