Seaweed has received a lot of positive press in recent years – and far beyond sensationalist claims about its alleged “superfood” properties. Promising studies have shown that feeding cows small amounts of seaweed can significantly reduce methane emissions, while around the world, startups are investing in seaweed farming to exploit its supposed sustainability benefits.
Now, a new research paper coming out of the US have used spatial analysis data to convincingly argue that planting seaweed beds could help prevent ocean “dead zones” and protect coastal ecosystems.
Nutrient pollution is a growing problem for our world’s waters. For humans, nutrients usually have a positive connotation, but there can definitely be too much of a good thing. When too many nutrients – namely nitrogen and phosphorus – end up in bodies of water, it leads to excessive algae growth. While these algal blooms temporarily create oxygen, they quickly die off, depleting oxygen levels in the water and killing marine life.
Unfortunately, fertiliser runoffs, which contain high levels of nutrients that help plants to grow, from the land are common. While we often think of agricultural pollution as affecting the air and skies, nitrogen and phosphorus used on farms often escape into our waterways and oceans, severely damaging marine ecosystems. Nutrient pollution has surged dramatically in recent years: between 2003 and 2013 alone, it rose globally by 65 per cent.
Seaweed farming is one of the few known ways to remove excess nutrients from water. By strategically planting seaweed in coastal ecosystems, the effects of harmful algal blooms could be mitigated. Seaweed has a longer life cycle than other algae, which prevents upheaval in the ecosystem, and their fronds can lock in nutrients such as nitrates and phosphorus.
Researchers in the Seaweed Working Group have been exploring the potential of seaweed aquaculture to tackle this problem. Taking the Gulf of Mexico as their case study, the group has made a case for the US to include seaweed farming in their strategy for managing nutrient pollution.
The Gulf of Mexico contains one of the largest hypoxic zones – an area deprived of oxygen – in the world, estimated at 18,000 square kilometres. This is largely due to excess nutrients washing down the Mississippi River. In May 2019, the river dumped an average of more than 5,000 metric tons of nitrate and 800 metric tons of phosphorus into the gulf on a daily basis – colossal numbers that are hard to fathom.
Using spatial analysis data, the researchers identified suitable areas for seaweed cultivation in the gulf. They found that a large area – roughly 63,000 square kilometers – was potentially available for seaweed aquaculture, more than enough to reach the US’s regional pollution reduction goals.
In addition to the tangible environmental benefits, the researchers predict that a rise in seaweed farming could also be a boon to the economy. As it stands, nutrient pollution hugely undermines fisheries in the Gulf of Mexico, which provide huge numbers of local jobs that make up much of the US seafood market. Aside from that, seaweed could also contribute to water quality trading schemes, through which companies offset their negative environmental impact by buying credits in sustainable initiatives.
Seaweed also has a host of other commercial uses that could be harnessed in tandem with the expansion of seaweed aquaculture. While seaweed exposed to high levels of pollution might not be safe to eat, it can also be used to make fabric, (edible) bioplastics, and biofuels.