plumes out in the clear shallow waters

Size
Height: 10–25 cm
Lifespan
1–3 years
Diet
Photosynthetic. Draws energy from sunlight and nutrients from surrounding water. Requires clean water and good flow.
Habitat
The red feather algae grows on rocky reefs throughout New Zealand – from the Three Kings Islands down to Stewart Island, in the low intertidal and shallow subtidal zones. It is a creature of the clear water, the sun-dappled reefs, the places where the light filters through. It forms fine, feathery, branching fronds that look like tiny red feathers or delicate plumes. It is beautiful, but it is not from here. It is slightly invasive, and it is definitely persistent.
Range
New Zealand - found throughout the North and South Islands on rocky reefs in low intertidal and shallow subtidal zones of clear, sheltered waters. Most common in the North Island and northern South Island. Native to Australia and New Zealand (some debate), but has spread to other parts of the world where it is considered invasive. Forms fine, feathery, branching fronds that look like tiny red feathers or delicate plumes.
Endemism
Introduced
Main Threats
None significant - this species is common and widespread. Localised threats include coastal development, pollution, and climate change affecting water temperature. Classified as Not Threatened, but potentially problematic as it has spread to other parts of the world where it is considered invasive. Native to Australia and New Zealand (some debate), beautiful but definitely persistent.
Population
Not Threatened, but potentially problematic. Red feather algae is native to Australia and New Zealand, but it has spread to other parts of the world, where it is considered invasive. In New Zealand, it is common on rocky reefs throughout the country. It is not rare. It is just very, very feathery and very, very persistent.
Conservation Status
Not Threatened
Human Risk
harmless
Handling Note
marine algae, safe to handle
Conservation Note
Introduced red algae; invasive in some coastal areas, not subject to conservation assessment.
Te Ao Māori
No recorded Māori name distinguishes the red feather algae from other red seaweeds. It was likely grouped with other red seaweeds called karengo. The feathery, red plumes would have been noticed. They looked like the feathers of a bird. Like the plumes of a chief. Like something precious and rare. The red feather algae was sometimes used as a decoration. The delicate, feathery fronds were gathered and dried. Then worn in the hair or woven into garlands. Today, the red feather algae still grows on the rocky reefs of New Zealand. You can see it at low tide. A flash of red in the clear water. You can touch it. Feel its soft, feathery texture. It is the beautiful one. The persistent one. The one that keeps coming back. It has been here for millions of years. It will be here as long as the light still reaches the bottom.
It refuses to die. An alga that keeps coming back. Asparagopsis armata is the beautiful one. An alga that looks like a feather. Its fronds are fine, feathery, and branching. Like tiny red feathers or delicate plumes. The colour is a bright pinkish-red. Sometimes with purple highlights. The fronds are soft and flexible. Waving gently in the current. It looks like something that might be worn in hair. Not something that grows on a rock. An alga that belongs in a craft shop. What makes it special? The persistence. The red feather algae is a survivor. It grows on rocky reefs. On shells. On other seaweeds. It can tolerate a wide range of conditions. From sheltered bays to exposed coasts. From low light to bright sun. It reproduces by releasing spores and by fragmentation. A tiny piece broken off can grow into a whole new plant. It is the weed of the reef. The one that keeps coming back. An alga that refuses to die. The red feather algae has a secret weapon. It produces chemicals that deter grazing by fish and sea urchins. These chemicals also have anti-bacterial and anti-fungal properties. The algae is being studied for its potential use in medicine and agriculture. Biologically, the red feather algae is a red alga. It has a complex life cycle. Alternating between a large, feathery stage and a small, crustose stage that grows on the surface of shells. The reef is shallow. The red feather waves in the current. Pinkish-red and delicate. A sea urchin approaches. Then turns away. The chemicals warn it off. The alga does not know it is being studied for medicine. It just wants to not be eaten. Not Threatened, but potentially problematic. Red feather algae is native to Australia and New Zealand. But it has spread to other parts of the world. Where it is considered invasive. In New Zealand, it is common on rocky reefs throughout the country. It is not rare. It is just very, very feathery and very, very persistent.