by Dennis Mombauer  Courtesy Mongabay

• Seaweed farming is an increasingly important part of the global food system and provides a range of benefits, including sustainable coastal livelihoods and economic diversification, food production, export revenue, climate change mitigation and adaptation, pollution control, and organic fertilizer.
• Sri Lanka used to have a prominent seaweed market in the 1930s, but today there’s only limited, small-scale seaweed farming in the country, mostly without processing or value addition.
• With greater investments of money, technology, and know-how, Sri Lanka could offer the perfect location to cultivate seaweed either on its own or as integrated mariculture, for example with shrimps, mollusks, or sea cucumbers, experts say.
• Farming seaweed in Sri Lanka could be a viable and highly beneficial part of expanding the blue economy if initial challenges are overcome and coastal communities engaged with support, guidance, technology, and quality control, experts say.

COLOMBO — In its territorial waters and exclusive economic zone, Sri Lanka is home to an abundance of coastal and marine resources. And while national policies and development visions already aim toward a blue economy, much of this natural wealth is currently not being used in a sustainable way or to its full potential, experts say.

Coastal fishing communities are vulnerable,” says Ruchira Cumaranatunga, a senior professor in the Department of Fisheries and Aquaculture at the University of Ruhuna. There is a need to create or enhance alternative livelihoods in coastal areas of Sri Lanka. While helping coastal fishermen to sustain their fishery activities, they should be provided with additional sources of income. The best method for this would be to promote small- and medium-sized enterprises based on fish processing, utilization of fishery waste or trash fish, and seaweed farming. Women and school dropouts in fisher families could be involved in these SMEs.”

The benefits of seaweed

Seaweed farming in particular offers a pathway for developing the blue economy and creating sustainable livelihoods, proponents say. Globally, seaweed aquaculture is one of the fastest-growing components of food production, with 99% of production taking place in Asia. If the sector is scaled up further, it could generate 500 million metric tons dry weight by 2050 and completely replace fishmeal and fish oil in animal feed, provide protein for humans, and save vast amounts of land and freshwater. There are many other ways in which seaweed is beneficial for humans, the environment, and the climate.

The commercially valuable types of seaweeds are species of algae that generally fall into three groups: green algae (Chlorophyta spp.), red algae (Rhodophyta spp,), and brown algae (Phaeophyta spp.). The different species of seaweed have many uses, and farming them has a small environmental footprint, as they do not significantly alter the existing coastal environment or require fertilizer input, freshwater resources, or medicines.

Seaweed species like Ulva lactuca [sea lettuce], Caulerpa racemosa, or Caulerpa lentillifera [sea grapes] are popular delicacies,” says Isuru U. Kariyawasam, a lecturer in the Department of Botany of the University of Sri Jayewardenepura. In addition, chemicals extracted from seaweeds can be widely used as nutraceuticals, pharmaceuticals, UV blockers, anti-cancer compounds, and many other applications.”

Dilanthi Koralagama, a senior lecturer at the University of Ruhuna, says seaweed farming could provide inputs for the organic fertilizer industry as well. As some seaweeds and microalgae contain comparatively high percentages of nitrogen,” she says, issues related to nitrogen content in organic manure can be solved up to an extent, which is not possible using terrestrial flora and fodder alone.”

Seaweed can be grown rapidly and vertically, which makes efficient use of available water space and provides an opportunity to diversify the coastal blue economy. However, providing a sustainable source of income and employment for coastal communities is only one of the many benefits and opportunities that seaweed could provide.

Seaweed farming can provide alternative livelihoods,” says Sarath Jayanatha, research officer at the National Aquatic Resources Research and Development Agency (NARA). Income generation is a major output of seaweed farming, but if it can be initiated on larger scales, seaweed could also be important to mitigate climate change.”

Seaweed is highly versatile and useful when it comes to addressing the causes and impacts of climate change. On one hand, seaweed stores carbon dioxide, and can be used for biofuel generation, replacing inorganic fertilizer, or lowering methane emissions as cattle feed. On the other hand, seaweed is an effective adaptation tool that can reduce wave energy and protect shorelines, improve water quality, and alleviate the local effects of ocean acidification and oxygen loss.

Furthermore, seaweed can be used to clean up pollution in the marine and coastal environment by removing agricultural nutrient pollution. Such pollution is difficult to remove once it has entered the water, and seaweed is one of the few effective methods to address it.

Seaweed farming in Sri Lanka

Currently, seaweed farming is only done on a small scale in Sri Lanka,” Cumaranatunga says. The seaweed is dried and exported without any value addition. Sri Lanka has a lot of living and non-living resources in the coastal belt, but at the moment, they are extracted and sold to other countries. Value addition within Sri Lanka could be a hugely important topic.”

Sri Lanka’s coastline abounds with seaweed species and habitats, for example along the southwest coast from Ambalangoda to Galle, or along the northern coastline near Jaffna, Palk Strait, and the Gulf of Mannar.

Seaweed farming or cultivation is a cheap, low-technology practice that requires little input and has been practiced in many Asian countries for decades or centuries,” Kariyawasam says. However, in Sri Lanka, it is still in its infancy. We have many sheltered bays, lagoons and estuaries that could be used, but so far, no large-scale attempts have been made to establish seaweed mariculture in the country.”

If such large-scale attempts would be made and seaweed farming enhanced alongside the coastal sector and its blue economy, Kariyawasam says, it opens up a future of many possibilities: Integrated Multitrophic Mariculture (IMM) systems are a very effective and sustainable method to culture seaweeds. Seaweed could be farmed in polycultures with shrimps and molluscs and even help to address problems of aquatic pollution and effluent water treatment for existing shrimp farms. Seaweed mariculture could also be integrated with sea cucumber farming to open up novel avenues for sustainable mariculture systems.”

Koralagama highlights the economic potential: Some seaweed species provide edible protein and are recommended as a dietary supplement. Growing such seaweeds for export could bring foreign exchange into the country, as there is already a well-established market in developing countries.”

Challenges and perspectives for Sri Lanka

Given all these benefits and applications, what is the potential for seaweed farming in Sri Lanka? If it is indeed a viable source of livelihoods that offers a range of co-benefits, why has it not been adopted at a larger scale yet?

Jayanatha from NARA says many companies are trying to get subsidies through seaweed projects. Therefore, many of these companies are not willing to invest their own money,” he adds.

It is important to note that seaweed farming requires sufficient capital and proper technical know-how to be set up,” Koralagama says. Therefore, support from the private sector is essential to scale up the seaweed industry in Sri Lanka.”

Even with financial support, however, there are still barriers and challenges that have to be overcome, Kariyawasam said. Some of the constraints to build a strong seaweed industry in Sri Lanka are lack of awareness and knowledge, lack of technology dissemination, lack of seed stocks, personal attitudes and lack of motivation among fishing communities, environmental fluctuations, and the short, seasonal lifecycles of certain seaweed species. Sri Lanka had a solid seaweed market in the 1930s, but it was lost due to adulterations done by our people. Therefore, it is very important to make high export-quality stocks when improving the seaweed industry in Sri Lanka.”

The scope to expand seaweed aquaculture is also limited by the availability of suitable areas, competition for these areas with other uses, the availability of engineering systems capable of coping with rough sea conditions, and market demand for seaweed products.

As the world increasingly becomes aware of the potential of a sustainable blue economy, investing in seaweed could provide many benefits for Sri Lanka, the experts say. In addition to providing a relatively cheap and low-technology option for economic diversification of coastal communities, they point out, seaweed farming also offers a range of use cases as well as serious co-benefits related to climate change mitigation, resilience, environmental protection, and pollution cleanup.

Banner image of seaweed on the beach near Mannar in northern Sri Lanka, courtesy of Dilanthi Koralagama.