Growing up Korean-American, I ate a lot of seaweed. My mom often made kimbap, vegetables and rice wrapped in seaweed, for me to eat at school. Every year for my birthday, I ate miyeokguk, a seaweed soup. I would have dried and salted strips of seaweed as a midnight snack. Seaweed has always been a huge part of my upbringing and diet, so I did not think much of it and never considered that it would have the potential to save the planet — starting with our oceans.
Over the past decade, our oceans have suffered from eutrophication, a process in which nutrients cause excessive algae growth and kickstart a chain of detrimental environmental effects such as low dissolved oxygen (DO) conditions. Sewage and agricultural runoff like fertilizer and pesticides are appetizing sources of nitrogen and phosphorus that overfeed algae and microbes. As a result, DO decreases to the point of hypoxia where there is less than 2 ml of oxygen per liter of water, leaving sealife gasping for air. When the hypoxic zone expands past its area of origin, anoxia, a total absence of oxygen, is established, and microbes reign supreme, releasing toxic compounds and forming dead zones.
So where does seaweed come in? Seaweed has a knack for getting rid of inorganic nutrients like nitrogen and phosphorus in the water and for increasing DO levels. Thus, scientists have proposed seaweed aquaculture, also known as aquatic farming, to turn the tides in the fight against eutrophication. However, there are some concerns about this solution: sites for seaweed farms may require destroying the habitats they were meant to protect and large scale cultivation necessitates adding artificial, potentially harmful materials to the water. Additionally, transporting seaweed to hypoxic areas could introduce new diseases and invasive species.
To improve this proposal, I suggest integrating plant nanobionics, a new field of science aiming to introduce non-native structures and functions to a plant, to transform seaweed farms into monitoring systems. Using spinach as their model, a team of chemical engineers inserted carbon nanotubes — cylindrical molecules made of rolled-up sheets of single-layer carbon atoms that are able to sense a variety of compounds — into spinach plant leaves. When the spinach roots draw in compounds of interest from groundwater, the leaves detect those compounds around ten minutes later, allowing the nanotubes to emit a signal and notify the lab.
Though both are green and leafy, spinach is a plant and seaweed is not. Seaweeds are actually protists, but there is still potential for plant nanobionics to be applicable. Seaweeds absorb nutrients from the water through the surface tissues of their “leaves,” or, more accurately, their blades, so I propose inserting the carbon nanotubes from the spinach model into seaweed leaves. In doing so, scientists could monitor the nitrogen and phosphorus levels in the water, as the inserted nanotubes would notify them when the seaweeds absorb those nutrients.
All in all, seaweed is not just delicious, it is also a promising step toward making informed decisions about eliminating eutrophication. Seaweed aquaculture has potential in increasing DO levels in the ocean while monitoring compounds in the water, acting as both a treatment and monitoring solution.
This article was edited by Narisara Mayer and Marianela Luna-Torrado.