By Jasmine Oropeza
Human activities—including fossil fuel combustion, fertilizer use, and mining—have upset the balance of the ocean by resulting in excessive amounts of nitrogen and carbon dioxide in the water. The harmful effects of excess nitrogen—which often enters the ocean via fertilizer-saturated runoff—include diminished food sources and habitats, increased algae growth, and decreased oxygen levels. In facing climate change, the ocean has absorbed 50 times more carbon dioxide than the atmosphere, rapidly declining its health. Bivalve and kelp aquaculture has emerged as a way to counter these challenges by reducing excessive amounts of carbon dioxide and nitrogen in the ocean.
Bivalves, including shellfish such as mussels and clams, naturally filter nitrogen from the environment by absorbing it into their shells and tissue as they grow. Bivalves can filter up to 50 gallons of water a day. A study conducted by the University of Florida revealed that 136 million aquaculture-raised clams were able to remove 25,000 pounds of nitrogen from the coastal environment and store 760,000 pounds of carbon. By filtering nitrogen from the ocean, these shellfish allow aquatic life to flourish in less polluted waters.
Kelp and seaweed also have the capability to filter and remove excess amounts of carbon dioxide in the ocean while producing oxygen through the process of photosynthesis. Dr. Diane Kim—marine microbiologist, kelp biologist, and founder of Holdfast Aquaculture—connects the environmental importance of kelp aquaculture to its potential as a sustainable food source.
“Seaweed provides a food source, a habitat, and nursery grounds for so many marine species contributing to a healthy marine ecosystem as they grow. Once they’re grown, they provide a great nutritional benefit for humans.” Dr. Kim explains.
Kelp counteracts the negative impacts of ocean acidification—the reduction of the ocean’s pH levels due to excessive absorption of carbon dioxide—on bivalves and improves their growing conditions. When left unchecked, acidification slows the growth of fish and shellfish and can prevent shell formation in bivalve mollusks. Using the symbiotic relationship between bivalves and kelp in aquaculture can help mitigate the impacts of ocean acidification on bivalves while simultaneously allowing the kelp and bivalves to absorb excess carbon dioxide and nitrogen.
Critics of bivalve and kelp aquaculture criticize large-scale aquaculture practices because of their ability to alter population genetics and propagate disease. In response, Dr. Kim says, “We [Holdfast Aquaculture] focus on locally sourced/adapted bivalves and seaweeds. Growing on a large scale in wrongful ways can propagate disease, introduce invasive species, and harm the ecosystem. If you manage it well, you can monitor the operation so that you are making sure that you are indeed having a net positive impact on the environment.”
Holdfast Aquaculture focuses on locally-grown bivalves and has introduced a mussel breeding program that chooses superior mussel genetics for improved genetic pool with more healthy and robust mussels. By growing locally sourced bivalves, Holdfast contributes positively to the environment while feeding the community.
“Aquaculture can be beneficial for the environment, ocean ecosystems and for tackling food insecurity in the world,” Dr. Kim says. “We hope to see an aquaculture industry that is rooted in sustainable community supported models. With kelp and bivalves, we are bringing life back into the ocean.”
About Author: Jasmine Oropeza is a pre-veterinary student at the University of California, Davis studying Animal Science and Public Health. Having more than 4 years of experience with different animal organizations within the Bay Area, she advocates for the importance of climate education, animal welfare, and accessible veterinary care. When not at UC Davis, Jasmine spends time with her pets in San Pablo, CA.