From seafood to seaweed

credit: Susie Emmett

Senegalese coastal communities are harvesting the spoils of the sea to generate extra income, whilst also revitalising the soil on their farms. Fishing has traditionally provided a valuable food source for local people, particularly during the dry season when crops cannot be grown. However, fish stocks off the coast of Senegal are declining and the coastal population has had turn to alternative produce from the sea to help sustain their livelihoods. With support from local researchers, villagers are harvesting and selling red algae (seaweed) as a source of carrageenan, a thickening agent which is used in a range of products including food products and cosmetics. Studies conducted on coastal farms have also shown that the seaweed can be composted and applied to crops as an organic fertilizer.

The red algae occurs naturally off the coast of Senegal as a result of the coastal winds (trades, monsoons and harmattan) stirring the currents that oxygenate the water and bring nutrients to the surface. Several types occur but researchers have focused their efforts on collecting and cultivating a variety of drifting algae (Hypnea musciformis) to avoid over-exploitation of stationary algal stocks. This particular variety anchors itself to a natural host, such as gorgonian coral, which grows in shallow water near the shore. However, to provide algae, which is free of contaminants (sand or aquatic plants), villagers have created a simulated coral host using thick nylon webs attached to ropes that extend ten metres beneath the water's surface. Once the algae attaches to the ropes, it grows rapidly increasing in weight by up to ten times in two months, when it is harvested.

credit: Susie Emmett

Significant benefits have already been achieved from harvesting this seaweed by selling it unprocessed and by using it as compost to increase crop yields. The compost can also be mixed with chipped wood for use in reforestation projects. However, researchers hope that villagers will soon be able generate additional income by processing the algae as a source of semi-refined carrageenan.

The Philippines currently produces the majority of carrageenan world-wide (80%) from two species of red algae, which are particularly well-suited to underwater farming, Eucheuma cottonii and E.spinosum. In total, seaweed farming provides a livelihood for at least 80,000 farmers in the Philippines and, in the Mindano coastal region where most of the seaweed farms are located, one of the key contributions of this industry has been the notable decline in blast and cyanide fishing. However, although 85% of the world market for carrageenan is dominated by exports from the Philippines, the Senegalese hope to tap into the niche market, which at present accounts for about 10% of the current global volume.

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