Aquaculture: Nori

Nori is the Japanese name for seaweed and a common component of sushi. Nori is made using red algae belong to the genus Porphyra; it is shredded and dried into sheets which are used to wrap sushi rolls.

Dried sheets of Nori, as would commonly be used to wrap sushi rolls. From: https://upload.wikimedia.org/wikipedia/commons/b/be/Nori.jpg

Porphyra grows on rocky coasts around the world. They are capable of surviving periods of total dryness, and are often found at the upper edges of intertidal zones. Blades can range from less than an inch to several feet in length.

Porphyra have a complex life cycle; The thallus, or body, of Porphyra you can see in a tide pool, produce male and female cells which are released into the surrounding water. Male cells fertilize the female cells, forming spores, which are themselves released into the water before settling and boring into shells, where they grow into a filamentous mass called a conchocelis. The conchocelis, under certain conditions, release spores that will grow into a new blade.

Life cycle of Porphyra yezoensis, from Takahashi and Mikami (2017). https://www.frontiersin.org/files/Articles/238074/fpls-08-00062-HTML-r2/image_m/fpls-08-00062-g001.jpg

Aquaculture of nori is most common in China, Japan, and Korea, but is growing in North America. A two-stage process is required to grow nor because of its complex life cycle. During the first stage, usually between May and October, the filamentous conchocelis stage nori are placed in a reservoir with seawater and nutrients to induce spore production. Following this phase, temperature and light intensity are manipulated to induce the release of spores, which are collected on nets; when spore release reaches are certain threshold, light intensity is increased to encourage growth of the thallus stage of Porphyra. Once settled on nets, Porphyra are grown in the sea or intertidal waters, and harvested after 40 or 50 days.  

Porphyra ready for harvest, from: http://english.jschina.com.cn/PhotoGallery/201203/t966519.shtml

This has been On the Ocean, a program made possible by the Department of Oceanography and a production of KAMU-FM on the campus of Texas A&M University in College Station. For more information and links, please go to ocean.tamu.edu and click “On the Ocean.

Contributing Professor: Dr. Lisa Campbell

Script Author: Martha Navarro

Editor: James M. Fiorendino

Featured image from: https://upload.wikimedia.org/wikipedia/commons/3/36/Porphyra_umbilicalis%2C_Porphyra_purpurea_Helgoland.JPG