Article by Duncan Murray and Dr. Yue Liu.
Around the planet, nearshore regions play a vital role in supporting local communities’ economic and cultural well-being. However, a confluence of various factors, including climate change, overfishing, and eutrophication, are threatening the viability of these regions. Researchers have known that seaweed farming could be a potential counterweight to these threats, but where to undertake such farming was previously unclear. Dr. Yue Liu, a postdoc at Xiamen University, has shed light on that question in his recent paper titled “Global estimates of suitable areas for marine algae farming.”
Seaweed is an ideal mariculture crop in the nearshore region because it can help preserve biodiversity. When asked how, Yue explained that seaweed is an effective mitigator against a notoriously disruptive process: eutrophication. Agricultural fertilizers contain nutrients critical in fostering crop production, like nitrogen and phosphorous. Rainfall sweeps these nutrients into nearby rivers, which carries them into the ocean. Upon exceeding a normal level, nitrogen and phosphorous abet an irregular, foul-smelling phytoplankton bloom that disturbs a once-balanced ecosystem.
Algal blooms then limit light penetration, reducing bottom-dwelling plant growth and impairing predators that rely on light to hunt. High algal photosynthesis rates deplete inorganic carbon and raise pH levels, impairing organisms’ chemosensory abilities. When these blooms die, microorganisms decompose the dead organic material, depleting oxygen and creating hypoxic “dead zones.” The ecosystem thus finds itself in a eutrophic state, and life – for aquatic creatures and fisheries alike – becomes doubly difficult.
Seaweed combats this process by absorbing considerable amounts of nitrogen and phosphorous, thus restoring the ecosystem to one rich with biodiversity.
Beyond its ability to protect nearshore ecosystems from unhealthy chemical processes, we can use seaweed for a diverse range of purposes. A staple of many dishes popular in Asian countries, seaweed can help solve food security issues, particularly in areas where overfishing, climate change, and other factors have greatly diminished previously reliable food sources. Yue confided, however, that he’s “not a big fan of seaweed; I don’t want to eat it every day, although it is a solution” and added, with a grin, that many others don’t seem to care much for it either. Fortunately, there are many exciting ways that seaweed is being used, including for biofuel production and as a “low-emission alternative for industries as diverse as textiles, bioplastics, and fertilizers.” Seaweed farming has something for everyone.
Seaweed is a remarkable plant, with many practicable functions – but where can we grow it? That was the question guiding Yue’s research. He and the project’s co-researchers employed what are called species distribution models (SDMs) to decide where seaweed might be most effectively cultivated. Yue explained SDMs by using a dog analogy. There are innumerable factors contributing to a dog’s survival in a particular ecosystem, but a few are significantly more influential than others. For instance, Yue explained that a dog can survive in an ecosystem between a specific temperature range. Outside of this range, a dog is unlikely to survive. Other important environmental factors might be the proportion of oxygen in the air, accessibility of food sources, and predation risk. SDMs model where dogs are most likely to survive by only considering factors contributing most to an organism’s survival. Through this approach, researchers determine where organisms can live, without having to take into account the seemingly infinite, minor variations from one region to the next.
Yue and his colleagues determined that while Australia, Indonesia, Russia, and Canada have the most suitable farming area in absolute terms, countries like Saudi Arabia, Sudan, Cameroon, and Tunisia possess the coastlines most ripe for seaweed farming, in proportional terms. His new project involves determining where mariculture farmers should begin growing seaweed, building on insights from his latest research.
