Types of Seaweed
What is seaweed?
Seaweed is not a weed in the invasive sense, and is not in the same family as a land plant but it does use photosynthesis in a similar way. Sea plants are marine algae that can vary in size from microscopic like phytoplankton to quite large as seen in kelp forests. Generally, what we think of as seaweed are marine macro algae.
While the definition of seaweed is not exact, there are three main categories of multicellular algae that make up most seaweed: red, brown, and green.
Similar to the role land plants play in a land ecosystem, seaweed plays an important role in the ocean ecosystem as a converter of carbon dioxide into oxygen and as a food source for creatures at the bottom of the food chain. And, it’s not just the ocean that benefits. The ocean, via seaweed, actually produces more clean air for the planet than trees do (source).
Red Seaweed
Red seaweed grows the deepest in the ocean and has the most varieties, estimated at 6,200. Well known and commonly eaten red macro algae include: nori, dulse (aka dillisk), carrageen (aka Irish moss), and laver.
Brown Seaweed
Brown Seaweed is the largest of the three types of macroalgae, with about 1,800 varieties, and likely what you see as a nuisance at the beach. Within brown marine algae, there are a couple notable families like Laminariaceae (aka kelps) which include kombu (kunbu), giant kelp, sugar kelp, and wakame, and Fucaceae (aka wracks) which include bladderwrack, serrated wrack, egg wrack (aka rock weed , knotted wrack), and channel wrack.
Green Seaweed
Green macro algae (multicellular) and green micro algae (unicellular) grow in freshwater and sea water. Common marine (sea) microalgae include: sea lettuce, gut weed, and chlorella. Spirulina is a unicellular blue-green algae that is often heralded as a superfood, but doesn’t count as seaweed if your definition is based on marine macro algae.
sources: Seaweeds by Ole G Mouriten, seaweed.ie, Wikipedia