What are seaweeds?
Seaweed is the umbrella term for a group of macroalgae (multicellular organisms) that live in salt water, brackish water or freshwater. Unlike land plants, seaweeds don’t have roots, but instead a ‘holdfast’ where they attach to shells, other weeds and rocks, and some will just float. Supporting the leaves is a stalk, connected to the holdfast. They absorb the sun’s energy, nutrients from the ocean and practice photosynthesis, releasing oxygen into the atmosphere. Many scientists believe the ocean contributes over 50% of the earth’s oxygen.
Seaweeds (macro algae) and algae are found around the world. There are thousands of species which differ vastly from each other, just as land plants do. Different seaweeds grow at different latitudes and also different depths in the ocean. There are three main colour groups – red, green, brown and blue. Macro-algae (seaweeds) are grouped as follows:
- ‘Green seaweeds’ are normally found in shallower salt and fresh waters and tend to favour nutrient rich waters. Sea Lettuce (also known as Ulva) is a delicious green seaweed which is bursting with nutrients and can be used in lots of ways in the kitchen.
- ‘Brown seaweeds’ are almost exclusively found in salt waters, and prefer colder temperatures. Kelp (some can grow up to 60m long) and Wakame are popular edible brown seaweeds.
- Typically ‘red seaweeds’ live at the deeper depths (up to 250m) and mostly prefer warmer waters. Examples of popular edible red seaweeds are karengo (used in sushi), dulse, Irish Moss and Agar.