Is seagrass the same as seaweed?

How it works

Seagrasses came from plants that once lived on land and later moved back into the sea. Like land grasses, they have roots and leaves, and they flower and make seeds, but the flowers open underwater and water carries the pollen. Seaweeds grip rocks with a holdfast and have no true roots, leaves or flowers.

Large patches of seagrass form meadows, like underwater grasslands. Small fish, shrimp, seahorses and shellfish hide among the blades, and many young fish grow up there. Seagrass also calms waves, and its roots hold mud and sand in place, helping keep the water clear.

Seagrass takes in carbon dioxide during photosynthesis and traps fallen leaves and bits in the mud around its roots. That carbon can stay buried for a very long time, so seagrass is called a 'blue carbon' habitat. Protecting it helps slow climate change.

Where to see it in New Zealand

Seagrass grows in many New Zealand harbours and estuaries, such as Tauranga Harbour and Whangārei Harbour. At low tide you may see patches of thin green blades on the mudflats. Research shows seagrass beds are important nursery areas for young fish such as snapper.

Try it together

With an adult, visit an estuary or harbour edge at low tide. Look for thin, ribbon-like green blades of seagrass and compare them with seaweed clinging to rocks. Gently check among the blades for tiny snails or shrimp. Walk around the patches, not on them, and watch for soft mud.