I am going to take you for a walk on an ocean beach in Nova Scotia. This is a little beach on a bay, which means it is a little more protected than ones that face the open ocean. On this walk, we are going to look at seaweed.
Seaweeds are algae. They are plants but they are quite different than plants that grow on land. They have no roots and they do not make flowers. They also cannot stand upright on their own. Instead some have air bladders that help to hold them up.
Algae can be so tiny you cannot see it with the naked eye (microalgae), or it can be up to and over 100 feet long (macroalgae)! Microalgae can live in both fresh water and seawater. Macroalgae lives in salty seawater.
The major types of seaweed are green, red and brown. Most green algaes are found in shallow waters, brown are found a little further out, and red can live the furthest out of all.
Some seaweeds just float around by themselves, but many attach themselves to a rock, or a shell, or other hard surface like a boat, or sometimes even sand. They attach themselves by a holdfast that looks a bit like roots but it does not provide any nutrients for the plant.
Seaweeds use sunlight and carbon dioxide to make energy, and absorb nutrients from the water to grow. They produce oxygen which is what we need to live.
Twice every day there is a low tide and a high tide on the ocean. This is when the water moves higher up the shoreline and then back out to sea. This make the edge of the ocean have different zones: the “splash” zone which is usually dry, the “intertidal” zone which is underwater only during high tide, and the “subtidal” zone which is always underwater.
Many macroalgaes live in the intertidal zone which means that twice a day they are out of the water. The subtidal zone is where macroalgaes such as Kelp grow.
In storms, bits of seaweed are often torn away and wash up on shore.
Many seaweeds provide food and homes for animals, but maybe you didn’t know that seaweed is also used by people. Long before grocery stores, seaweed was used as a fresh vegetable in times of hardship, eelgrass (not actually a seaweed but a seagrass) was often used as to stuff a mattress or to insulate the walls of houses, and other kinds of seaweed were scraped off the beach to fertilize gardens.
Today, harvesting seaweed is a big business. It is harvested to be used as food (for animals and people), cosmetics, medicine, and fertilizer.
Art Project: Seaweed Art