Sustainable Seaweed Cultivation in the Caribbean

Welcome and GreenWave Introduction [00:00:06]

Hello and welcome to the GreenWave Spotlight. This is a webinar series showcasing regenerative ocean farming projects around the world. I’m Kendall Barbery, Director of Partnerships and Industry Engagement, GreenWave and your host and moderator for our spotlight on sustainable seaweed cultivation in the Caribbean.

For those of you who are not familiar with GreenWave, we’re a nonprofit organization based in North America with a mission to train and support regenerative ocean farmers in the era of climate change. We operate two ocean farms in the northeast US and produce kelp seed for farmers throughout the region. We also provide online and hands-on training for kelp farmers and seed producers, build infrastructure farmers need for success, and support value chain coordination to foster resilient and regenerative ocean farming across coasts. You can find us and a community of seaweed farmers online at hub.greenwave.org.

While most of our programming focuses on temperate kelps, we’ve also noticed a steady stream of interest in warm water seaweed cultivation in our global community since we launched our Hub in 2022.

Webinar Overview and Speaker Introductions [00:01:25]

During our webinar today, we’re going to hear from four fantastic speakers who were involved in producing the Guide to Better Practices for Sustainable Seaweed Cultivation in the Caribbean, released in summer of 2024. We’ll hear from co-authors of the guide from the University of Chicago Marine Biological Laboratory, the Nature Conservancy, and the Belize Women’s Seaweed Farmers Association. We’ll learn about the current state of seaweed farming throughout the region, delve into recommended cultivation practices, and discuss current and prospective market opportunities for coastal seaweed farmers.

Dr. Loretta Roberson is an Associate Scientist with the Marine Biological Laboratory based in Woods Hole, Massachusetts. Loretta earned a PhD from Stanford University in Biological Sciences focused on the biology and biomechanics of seaweeds. She currently leads an ARPA-E MARINER project to develop the offshore cultivation of seaweed and a study on how co-cultivation of seaweed and shellfish might enhance productivity and mitigate ocean acidification in tropical environments.

Dr. Gretchen Grebe is an Assistant Professor of Aquaculture and Marine Sustainability at Unity Environmental University. Gretchen is an aquaculture and environmental scientist who specializes in seaweed farming, water quality, and eco-entrepreneurship. She has over 15 years of experience developing practices for freshwater and marine resources and is a co-author of Better Practices for Sustainable Seaweed Cultivation in the Caribbean.

History and Current State of Caribbean Seaweed Farming [00:06:43]

Historically, wild seaweeds were harvested in the West Indies or the Caribbean region for the preparation of locally important drinks and desserts known as sea moss love more juices. However, very little information is available on production — what species are used and the sources of the seed material, the annual production from seaweeds, how much is harvested versus farmed.

Currently, farming in the region is limited to artisanal scale farms that produce less than 10 tons dry annually, but there is potential for expansion. Belize may be a good model for how to grow the industry in a stepwise manner.

Native red seaweeds like Eucheuma and Gracilaria are most commonly grown. Since the 1970s there’s been farming of Kappaphycus alvarezii, a red alga that’s native to the Indo-Pacific and exhibits much higher growth rates. These species are preferred because of their gelling properties — Eucheuma and Kappaphycus are high in carrageenan and Gracilaria is high in agar, and both are commonly used to thicken foods and drinks like the sea moss drink.

Cultivation systems for growing these species are varied throughout the region. In Puerto Rico, for example, a large-scale 200-foot by 100-foot system was piloted for deep water — a design some may recognize from kelp farms in the northeast and Alaska. But most farms used today fall into the shallow water off-bottom or floating raft categories that are both easy to install and do not require a lot of resources or initial investment.

Challenges Facing Caribbean Seaweed Farming [00:08:58]

The main challenges to seaweed farming in the Caribbean are not surprisingly different from other regions where seaweed cultivation is established or just starting. Farm sites must minimize conflicts with other uses such as tourism, often a major component of the local economy in the Caribbean, and also avoid areas where there are sensitive species like coral reefs that need to be protected.

The lack of availability and accessibility to shallow water that does not require specialized equipment like scuba, or areas where water quality is not conducive to good growth or food safety, increases the cost and risk of farming. Storms are a real threat to the region, and most countries lack seaweed policies or regulations around farming. Production is on a small scale that does not attract buyers in the global market.

Best Management Practices: Site Selection, Seed Sourcing, and Farm Monitoring [00:09:57]

To help overcome these challenges, a manual was developed that can help a rapidly growing industry adopt sustainable practices that minimize environmental impacts and ensure long-term viability. This document provides guidelines and recommendations for sustainable seaweed cultivation in the Caribbean, also known as Better Management Practices or BMPs, that promote environmental sustainability, economic viability, and social benefits in this developing sector.

Site selection has to be one of the most important factors to consider when starting a seaweed farm. This should happen during the planning phase and includes awareness of marine flora and fauna that might be present at or near the farm site, and social license — ongoing approval within the local community and other stakeholders. It must also consider the biology of the species being farmed and the optimal cultivation conditions required: bottom type, water temperature, salinity, light, and so on.

The source of seed material and nurseries to support seed stock are very important, but currently nurseries are not existent in the region. At present, most seeds are obtained by fragmentation from harvested material and supplemented by wild harvest. One bottleneck is the need for significant amounts of biomass to start farming operations, plus a need to replenish crops due to losses from seasonal conditions like high summer water temperatures, catastrophic loss due to storms, and the need for lineage development to increase disease resistance, increase growth, and enhance climate resilience. Establishing a controlled land-based nursery for this purpose is strongly recommended.

The monitoring and maintenance of seaweed farms are other key practices that can help limit biomass loss and increase farm productivity. Epiphytes, grazers, and disease can cause huge losses and often progress rapidly if not caught early. Common culprits include microalgae, microbes, and other seaweeds, and these can be aggravated by larger farms with higher stocking densities. It’s recommended that seaweeds are thoroughly cleaned before out-planting — this can involve gentle shaking in seawater or even a dip in fresh water — and the farm array should be cleaned frequently, at least once per week. During that time, the seaweed should also be checked for signs of stress or disease like discoloration or fragmentation.

Storm Preparedness [00:12:59]

Storms are becoming more frequent and damaging, and storm preparedness is increasingly important. Farmers need to ensure that the farm can resist damage from a storm, but also have a plan for when a storm is imminent. Regular inspection of lines and anchors can help avoid surprises during an emergency. An agreed-upon plan can help identify and prepare areas to store the crop during a storm — whether on the bottom of the ocean, in deeper areas, or in bags in a safe covered area on land — and thus save precious time. Having replacement gear and seeds on hand will help speed the return to normal operations in the case of damage or loss. Documenting the inventory — starting biomass, biomass at the time of the event, and normal mortality rates — may allow farmers to qualify for disaster assistance if available.

Market Opportunities for Caribbean-Grown Seaweed [00:13:58]

Existing seaweed products commonly produced and sold in the region include dried raw seaweed, drinks, and jellies — as well as a host of trial products being produced by entrepreneurs in the region, including skincare products, sweets, and agar.

Building transparency and traceability for these existing and emerging products will benefit both producers and consumers. A track-and-trace system would record key production details during farming, harvesting, processing, product testing, packaging, and labeling. Studies show that transparency in product authenticity, safety, and sustainability is important to consumers and helps overcome risk barriers associated with trying new products. Offering product traceability can also help seaweed farmers and processors evaluate and revise their biosecurity measures.

Many seaweeds native to the Caribbean could be commercially important. One study conducted by Díaz-Piferrer over 50 years ago noted almost 70 potential species of commercial interest, and there’s been relatively little exploration of the region’s seaweed resources since then.

The hydrocolloid market is by far the largest use of tropical seaweed biomass at a global level. Hydrocolloids are hydrophilic substances that form gels in the presence of water and are used in texturizers, thickeners, binders, cosmetics, and more. Alginate, agar, and carrageenan are all commercially valuable hydrocolloids produced from seaweeds. Given the Caribbean’s proximity to large manufacturing operations in Mexico and Central America and a larger North American market that uses these products, growing Caribbean seaweeds for hydrocolloid feedstock has significant economic potential — with the limitation being that production volumes must be large enough to attract buyers.

Section four of the BMP guide shares recommendations for how folks from almost any industry can support the growth of seaweed aquaculture in the Caribbean, grouped by sector: investors, nonprofits, local and national governments, researchers, entrepreneurs, and farmers themselves. Farmers who adopt better management practices may also find that pursuing a third-party sustainability certification like an ASC certification might return a higher price per pound for their seaweeds.

Belize: TNC’s Mariculture Development Work [00:23:05]

Seleem Chan, Mariculture Specialist and Safety Officer with the Nature Conservancy in Belize, leads community-based development of a sustainable mariculture industry in Belize and has over 20 years of protected areas management experience in both marine and terrestrial environments.

Belize is bordered by the Caribbean Sea to the east, Guatemala to the west, and Mexico to the north. Most of Belize’s income comes from the marine environment — tourism represents about 40% of GDP, with fishing and agriculture contributing around 14%. Belize is home to the world’s second-largest barrier reef.

TNC has been working with partners in Belize for a number of years to create a sustainable mariculture industry, developing regulations, increasing knowledge for farmers, and identifying financial tools to support industry growth. This work started with the members of the Placencia cooperative and also assisted in the development of the Belize Women’s Seaweed Farmers Association.

The industry idea itself came from fishers — visionary men and women sitting on an island dreaming of one day farming seaweeds. TNC and partners are now working to develop this industry jointly with the Belize Fisheries Department and the Government of Belize.

Cultivation System Design and Ecological Benefits [00:28:11]

The BMP document guiding Belize’s development was first created in 2018. Over the years it needed to be refreshed, and in that process it was split into two documents: a technical guide and a situation and analysis document for Belize focused on what has been occurring within the country over the years.

In terms of cultivation design, experiments first started with a floating raft. While the floating raft structure works at certain locations, due to climate change and other considerations, there was a shift to a submerged structure, with seeds hanging about a foot beneath the sea floor. The design is modular — farmers can start with one or two plots of 50-by-50-foot structures and add on as they progress, working toward farms of six to twelve plots.

Data collected by TNC in 2017 and 2018 showed significantly higher fish abundance within a seaweed farm compared to a control site. A seaweed farm functions as a nursery habitat for juvenile species. Lobsters and juvenile reef fish have been observed in abundance within healthy farms — it’s described as like swimming in an aquarium.

TNC and partners also hosted Belize’s first seaweed symposium, bringing together government, NGOs, private sector, and associations under one roof to discuss successes, challenges, and opportunities. Capacity building is a core part of the work — using the BMP documents to train stakeholders and ensuring the industry includes both men and women.

Products Being Developed by Belizean Farmers [00:31:35]

Products being developed by BWSFA members include dried seaweed ground to powder and encapsulated, seaweed shakes, seaweed gels infused with various fruits including cacao, and fresh-frozen seaweed for salads. The association recently acquired a powder machine to allow them to powder seaweed in-house, making it easier for others to use in research and development or different products.

Ongoing activities in Belize include: the government of Belize accepting mariculture policy in 2022 (developed with TNC and partners), ongoing work to develop accompanying regulations, and further study on Kappaphycus alvarezii — a non-native species — to ensure it can be cultivated without negative environmental impact. All of this is being done jointly with the Belize Fisheries Department and partners including BWSFA.

Belize Women’s Seaweed Farmers Association [00:35:45]

Jalima Martin Gold, President of the Belize Women’s Seaweed Farmers Association, introduced the BWSFA and its work. The association was founded by a small group of women in Placencia, Belize, around 2019 — all farmers, passionate about the water and the oceans. Many founding members work in the ocean in other ways, either in coral restoration or tourism, and have all grown up in the region.

The association’s goals include creating an equitable seaweed industry; enhancing Belize’s economy and providing real, sustainable, year-round livelihoods; supporting biodiversity and improving local environmental conditions; and reducing reliance on overfishing by giving fishing communities another source of income. Seaweed mariculture is described as very low-input farming, healthy for the waters and the oceans.

The BWSFA has built strong relationships with the Government of Belize, donors, partners, resorts, tour operators, and universities. Five out of 38 members have received small branding support for packaging and labeling. The association recently trained eight female boat captains — an effort explicitly tied to creating equality in the maritime landscape. Members have sun-dried over 17,000 pounds of wet Kappaphycus in the last year, and the association has hired women, youth, and men as part of operations. The board is women-led, but membership is open to men and youth in the community.

Climate Adaptation and the Case for a Community-Owned Industry [00:43:30]

The BWSFA has gathered data on the best times to farm, process, and harvest seaweed in Belize. Farming during cooler water temperatures — November through January — yields better retention rates. While these months bring northerly winds and cold fronts, the water temperature is ideal for seaweed growth.

On the question of what a seaweed industry in Belize should look like, Jalima was direct: the goal is to build something where Belizeans are not just the workers, but the owners. Developing regulations that support subsistence-scale farms, medium-sized operations, and larger investor-backed farms — while ensuring local communities share in the returns — is central to the BWSFA’s vision. Value-adding within Belize, rather than simply exporting raw seaweed, is a priority for keeping economic benefit in-country.

Q&A: Cooperative Model, Industry Scale, and Farm Startup Costs [00:48:20]

On the cooperative model and lessons learned, Jalima noted that forming a real legal association from the ground up is not easy, but having solidarity among a large group makes it possible to have a voice with policymakers and government. Her core lesson: stick it out. Building something big from the ground up takes time, but when you see the bigger picture, it’s very important.

On the scale of production across the Caribbean, Loretta noted that the industry is really just getting started again in many areas. A culture of sea moss drinks exists across many islands, but much of it relies on wild harvest. Challenges like financing and storms have made it difficult for people to get started in farming. But there’s a lot of ocean and a lot of potential, and conversations like these help aspiring farmers start off on the right foot — not from scratch.

On startup costs for a 50-by-50 farm structure in Belize, Jalima estimated approximately $1,000 USD, noting that materials like the polypropylene ropes used in the structures are expensive in Belize. The goal is to develop regulations that accommodate small subsistence farms, medium-sized operations, and larger investor-backed farms — creating a tiered system without driving an industry where local people are just the workers.

Q&A: Storm Resilience, Submerged Structures, and Climate Adaptation [01:02:55]

Brian Walker, a sea moss farmer and executive of the Eastern Caribbean Sea Moss Association, asked Seleem and Jalima about storm loss rates, noting that their farms lose around 80% of stock during severe weather events when using the sinking method. Jalima estimated Belizean farms may lose 20 to 30%, and mentioned that farm barriers — structures that catch seaweed when it detaches from the lines — could help reduce loss significantly. Theft was also cited as a significant challenge, particularly at unattended farm sites.

Loretta shared details on the submerged offshore structure piloted in Puerto Rico, designed specifically for storm avoidance. The buoys can be lowered or raised to the surface, and all lines are maintained under constant tension whether at the surface or on the bottom. When kept at the surface during a storm as a test, it proved to be sturdy. When the farm is lowered to the bottom and raised again, the seaweed adapts well — red seaweeds in particular adapt quickly to changing light environments.

Jalima added that the submerged structure isn’t only useful for storms — as ocean waters continue to warm, sinking the farm can cool the seaweed and reduce heat stress. She noted that November through January is the best planting window in Belize, coinciding with cooler water temperatures.

Q&A: Student Involvement, Aggregation, Aquarium Trade, and Permitting [01:09:00]

A college student asked how young people can get involved with organizations working in Caribbean seaweed. Seleem encouraged reaching out directly to the BWSFA and noted that TNC is actively developing relationships with universities in Belize. Jalima added that data collection is one area where student support would be particularly valuable, as farmers are not always equipped to manage that work.

Kendall noted that GreenWave’s online Hub has between 7,000 and 8,000 global users, including active farmers, scientists, and seed producers from around the world, and that joining the community at hub.greenwave.org is a great way to connect across geographies.

On aggregation challenges — getting enough volume from scattered small farms to attract global buyers — Seleem acknowledged that the industry is not there yet. Developing regulations, building an industry, and then thinking about cross-country aggregation to supply larger markets is the path forward. He hopes to eventually see a system where Caribbean nations can collectively supply buyer demand that individual countries cannot meet alone.

On the aquarium trade as a potential market for Caribbean macroalgae, Loretta noted that MBL had worked with a collector in Florida to identify seaweed species for the aquarium trade, but that demand is irregular and unpredictable. Logistically, exporting live seaweed from the Caribbean would be very challenging at the current stage.

On the regulatory pathway to start a seaweed farm in Belize, Seleem explained that approximately 20 permits have been issued to seaweed farmers by the Belize Fisheries Department, though not all may still be active. The current permitting process requires engagement with multiple government departments — Fisheries, the Department of the Environment, and the Lands and Geology Department — which is onerous. TNC and partners are working to develop regulations that would make the Fisheries Department a one-stop shop for permitting, removing much of the existing red tape. At present, no further permits are being issued until the regulations are finalized.

On marine spatial planning, Jalima noted that work is underway to identify the best locations for seaweed farms in Belize that don’t conflict with tourism or fishing. The BWSFA is also actively working to integrate seaweed farming into the tourism landscape — noting that visitors often want to take farm tours, and that there’s an opportunity to position farms as an attraction rather than an obstacle.

Seed Banking and Closing Resources [01:27:15]

On seed banking and biobanking for tropical seaweed species like Kappaphycus and Eucheuma in the Caribbean, Loretta acknowledged that formal biobanking is not currently being done. MBL holds several strains from the Caribbean and is working with partners at Kelp Bark to pursue funding for a more formal effort. A key challenge is that these species are almost never found in a reproductive state, making strain selection and seed protection difficult.

Megan Constantine from the Nature Conservancy announced an upcoming tropical seaweed aquaculture online course in development at TNC — compiling geography-specific BMP guides, monitoring and evaluation frameworks, citing resources, and ecosystem services of restorative farms into an interactive online course with modules spanning environmental benefits, farm management practices, and community engagement. The course was expected to be available shortly after the new year.

Kendall closed by inviting participants to access the Guide to Better Practices for Sustainable Seaweed Cultivation in the Caribbean, join GreenWave’s online Hub at hub.greenwave.org, and follow GreenWave on social media at @greenwaveorg.