carpets the intertidal rocky shore green

Size
Height: 1–5 cm
Lifespan
1–2 years
Diet
Photosynthetic. Grows on rocky shores, in rock pools, and on other seaweeds. Requires clean water, good light, and stable surfaces.
Habitat
Grows on rocky shores in intertidal and shallow subtidal zones. Forms low, dense, bristly mats that look like a greenish-red carpet.
Range
Found throughout the North and South Islands on rocky shores, in rock pools, and on other seaweeds. Most common in intertidal zones.
Endemism
Endemic
Main Threats
None significant. This species is common and widespread. Localised threats include coastal development, pollution, and climate change.
Population
Not Threatened. Turf algae is common on rocky shores throughout New Zealand, often forming dense mats on rocks in the lower intertidal.
Conservation Status
Not Threatened
Human Risk
harmless
Handling Note
marine algae, safe to handle
Conservation Note
Endemic red algae; not assessed by NZTCS as marine algae are outside the scope of current threat classifications.
Te Ao Māori
No recorded Māori name distinguishes the turf algae from other red seaweeds. It was likely grouped with other red seaweeds called karengo. The turf algae was a sign of a healthy intertidal zone. A rock covered in dense turf was a rock that was alive, a place where the small creatures could hide and feed. The stiff, wiry fronds were sometimes used as a gentle abrasive. They could be used to scrub wood or stone, or to clean fish scales from a knife.
It is the lawn of the intertidal zone. Gelidium caulacantheum has fronds that are short. Usually less than five centimetres tall. And stiff. Like tiny bristles. They grow in dense, crowded mats. Covering the rocks in a greenish-red carpet. From a distance, it looks like moss or short grass. Up close, it is a forest of tiny, branching seaweeds. Each one anchored firmly to the rock. It is the alga of the low growth. The one that covers the rock like a green carpet. What makes it special is the density. The turf algae grows in such dense mats that it creates its own microclimate. The mat traps moisture at low tide. Keeping the rocks damp. It traps sediment. Building up a layer of fine silt. It provides shelter for a whole community of tiny invertebrates. Crustaceans, worms, snails. That live in the spaces between the fronds. It is the alga of the community. The one that creates a home for others. The turf algae is tough. Its fronds are stiff and wiry. Made of a strong, flexible material. It can withstand the pounding of the waves. It is also hard to dislodge. Its holdfast grips the rock like glue. You can scrape at it with your fingernail. It will not come off. It is the alga of the tough surface. The one that holds on when others let go. Biologically, the turf algae is a red alga. It reproduces by releasing spores from specialised structures on its fronds. The spores are released into the water. Carried by the currents. They settle on nearby rocks to grow into new plants. To find turf algae is to find the greenish-red carpet on the rock. It is short, dense, bristly. The lawn of the intertidal zone. It does not stand tall. It does not wave in the current. It just covers the rock. Low and tough. Providing a home for the small creatures of the tide. It is the alga of the low places. The one that holds the rock together. No recorded Māori name distinguishes the turf algae from other red seaweeds. It was likely grouped with other red seaweeds called karengo. The turf algae was a sign of a healthy intertidal zone. A rock covered in dense turf was a rock that was alive. A place where the small creatures could hide and feed. The stiff, wiry fronds were sometimes used as a gentle abrasive. They could be used to scrub wood or stone. Or to clean fish scales from a knife.