Pyropia

Pyropia is a genus of red alga [seaweed] in the family Bangiaceae. It is found around the world in intertidal zones and shallow water. The genus has folding frond-like blades which are either red, brown or green. Some "Pyropia" species are used to create nori, and are thus important subjects for aquaculture.
Taxonomy.
"Pyropia" was originally erected by Jacob Georg Agardh, a botanist and professor at Lund University. Before this, and sometimes after, many species of "Pyropia" were placed in "Porphyra", a different genus of red alga. New species of "Pyropia" are still being discovered, for example in 2013 research done on New Zealand plants was able to move "Pyropia plicata" from "Porphyra".
Description.
"Pyropia" species are red algae with a discoid holdfast and short stipe. They have folded blades, which are membranous and monostromatic, coming in red, brown, and dark green colorations. These folded blades may also look like fronds until unfolded. These blades reach up to one meter in length in some species, but are generally around 20 centimeters in diameter.
Distribution.
"Pyropia" grows in intertidal zones and down to 10 meters in some bodies of water based on clarity and substrate. It grows in large swaths, attaching itself to stones and shells, covering most of the bottom. "Pyropia" can be found globally in warm-temperate and extratropical [cool] waters.
Ecology.
"Pyropia" species, which reside in the upper intertidal zone, endure many stresses, including intense direct light, temperature fluctuation, osmotic stress, salinity fluctuation, and desiccation. They are especially able to handle heat stress; some "Pyropia" species will halt metabolic systems that are not essential to homeostasis, such as photosynthesis. Other species will use increased lipid production to fight desiccation. The ability of "Pyropia" species to adapt to deal with these stresses makes them heavily studied organisms.
One of the threats to "Pyropia" is fungal infections by "Alternaria" sp. ZL-1, which has been observed in farming environments on "Pyropia yezoensis" "." The fungus kills "Pyropia" cells and leaves brown rust-like spots on the outside of the blades.
Use.
Within the genus "Pyropia" multiple species are used for nori (edible seaweed), "Pyropia yezoensis" and "P. haitanensis" being most popular. It is a two-billion-dollar industry with most major growers located in China, Korea, and Japan.
Nori contains substantial amounts of Vitamin B12 according to a 2014 paper. However, the Academy of Nutrition and Dietetics considers this source unreliable for vegans.