Seagrass meadows play a major overlooked role in feeding and nourishing coastal communities, according to a new study published in Cell Reports Sustainability and led by researchers at the Department of Ecology, Environment and Plant Sciences, Stockholm University.
Coral reefs are famous for supporting huge numbers of fish. But this study shows that seagrass meadows may be just as important, and in some cases even more important, for the fish that people actually catch and eat.
The research team studied fish from 20 seagrass meadows and 20 coral reefs along a 3,000-km stretch of coastline from Kenya to Mozambique. They looked at six key nutrients that people need to stay healthy like calcium, iron, zinc, selenium, vitamin A, and omega-3 fatty acids. Instead of looking at each nutrient one by one, the scientists treated fish more like natural multivitamins.
"Fish don't nourish people one nutrient at a time," says Benjamin Jones, doctor in marine ecology who carried out the research as a PhD student at Stockholm University and is now Chief Conservation Officer at Project Seagrass. "They come as a package. A single fish contains iron, zinc, calcium, selenium, vitamin A, and omega-3s. We wanted to understand which habitats produce fish with the best mix of these nutrients."
After accounting for differences in fish biomass, the team found that for the top three most important food fish species, nutrient support was over 8 times higher in seagrass meadows than coral reefs. On average, seagrass fish communities were 1.6 times more nutritionally rich than coral reef fish communities.
Two important food fish prized in the region, rabbitfish and parrotfish, were also far more common in seagrass meadows. In terms of biomass, they were 5 times and 65 times more abundant in seagrass than on coral reefs.
"We know that coral reefs have more fish overall, but seagrass meadows had more of the fish that really matter for local food," says Benjamin Jones. "This changes how we should think about these habitats. Seagrass isn't just a fish nursery, nor just a carbon stock, it's food infrastructure, nature's own supermarket."
The study also found that an average seagrass fish could provide around 5 per cent of a young child's daily iron needs, 70 per cent of their selenium needs, and 21 per cent of their zinc needs.
These numbers don't mean that every child eats this amount. The study measured the nutrients that could be available from fish, not what people consume. But the findings show that seagrass meadows play an overlooked role in supporting the health of coastal communities.
Millions of people in tropical coastal regions rely on fisheries for food and income, and many of these communities face poverty, limited livelihood options, and high risks of malnutrition.
The findings also challenge the way ocean conservation is often framed. Coral reefs attract global attention, and rightly so. They are rich in biodiversity and support major fisheries. But coral reefs are also under severe pressure from climate change, bleaching, ocean warming, acidification, and overfishing. Seagrass meadows are also declining, especially in tropical regions, because of poor water quality, sewage pollution, coastal development, sediment runoff, and physical damage. Yet they receive far less attention and funding.
The authors argue that this must change.
"Our results really underscore the need to protect seagrass meadows, which are often overlooked in the shadow of more well-known habitats such as coral reefs and mangrove forests, while at the same time avoiding fishery closures, as these could jeopardize one of the most important sources of nutritious food for local communities along tropical coastlines", says Johan Eklöf, professor in marine ecology at Stockholm University, and co-author of the study.
The study argues that seagrass should not replace coral reefs in conservation priorities. Instead, it shows that the two habitats do different jobs and need equal attention.
Coral reefs support more fish biomass. Seagrass meadows provide reliable access to key food fish that can contain a powerful mix of nutrients.
"Reefs and seagrass meadows work together," said Benjamin Jones. "If we want coastal fisheries to feed people, we need to protect the whole seascape."
Key findings
- Seagrass fish communities were 1.6 times more nutritionally rich than coral reef fish communities after accounting for fish biomass and depth.
- For the top three regional food fish species, predicted nutrient support was 8.4 times higher in unfished seagrass meadows than unfished coral reefs.
- In fished areas, predicted nutrient support from these same species was 8.8 times higher in seagrass meadows than coral reefs.
- Two important food fish were far more common in seagrass: Siganus sutor was 5 times higher by biomass, and Leptoscarus vaigiensis was 65 times higher by biomass.
- An average seagrass-associated fish could provide around 5 per cent of a young child's daily iron needs, 70 per cent of selenium needs, and 21 per cent of zinc needs.
- The study shows that seagrass meadows should be recognised as vital food-security habitats, not just biodiversity or carbon habitats.
