Seaweed is one of the mainstays of the marine products in Semporna. Seaweed is a loose colloquial term encompassing macroscopic, multicellular, benthic marine algae. The term includes some members of the red, brown and green algae.
Two specific environmental requirements dominate seaweed ecology. These are the presence of seawater and the presence of light sufficient to drive photosynthesis. Another common requirement is a firm attachment point.
The deepest living seaweeds are some species of red algae. Red algae are slow growing compared to green algae. They are attached to bottom or other hard surfaces, and are often most conspicuous in the intertidal region of rocky coasts and in tide pools. In the tropics they are found in all zones of the coral reef.
Red algae are unusual among the algae because they can include in their cell walls calcium carbonate which makes the plants hard and resistant to wear. Red algae that grow this way are referred to as "coralline" algae, because they are hard like corals.
The upright and crustose forms of red algae bind and infill coral skeletons to form massive sedimentary structures which are strong enough to resist wave-action and erosion. Fleshy red algae are also common on coral reefs.