tangles in the warm shallow rock pools
- Size
- Length: 5–20 cm
- Lifespan
- 1–2 years
- Diet
- Photosynthetic. Draws energy from sunlight. Requires still or slow-moving water, good light, and high nutrient levels. Tolerates variable salinity.
- Habitat
- Grows in shallow, sunlit waters throughout New Zealand. From Northland to Stewart Island. Rock pools, muddy bottoms, and surfaces of larger seaweeds. Bright shallows and warm pools.
- Range
- Found throughout North and South Islands in shallow, sunlit waters. Most common in sheltered coastal waters with still or slow-moving conditions. Also found worldwide.
- Endemism
- Native
- Main Threats
- None significant. One of most common and widespread algae in world. Localised threats include coastal development, pollution, and climate change affecting clarity.
- Population
- Not Threatened. One of most common algae in world. Found in fresh, brackish, and salt water on every continent. Abundant in rock pools and estuaries.
- Conservation Status
- Not Threatened
- Human Risk
- harmless
- Handling Note
- marine algae, safe to handle
- Conservation Note
- Native green algae; not assessed by NZTCS as marine algae are outside the scope of current threat classifications.
- Te Ao Māori
- No recorded Māori name distinguishes hair algae from other green algae. Likely grouped with other green seaweeds called rimu. Fine, green filaments would have been noticed. Looked like hair. Like hair of drowned person. Like green man of sea. Sign of still water. Of warm pools. Where sun reached bottom. Sometimes used as dressing for wounds. Soft, silky filaments applied to cuts and burns to stop bleeding.
It does not inhabit the deep exclusively. Cladophora albida looks like someone washed their hair in rock pool. Its filaments are thin, green, and silky. Like strands of wet hair. They grow in dense mats. Covering rocks, shells, and other seaweeds in green, slimy blanket. Run fingers through it. Feel silky texture. Way it clings to skin. It is alga of hairy surface. Makes rock pool look like shower drain.
What makes it special is simplicity. Hair algae is simple green alga. Single, branching filament of cells. Each connected end to end. No complex structures. No floats. No specialised parts. Just grows. Branching and branching. Forming tangled mat of green threads. Under microscope, filaments are beautiful. Each cell perfect cylinder. Branches forming at precise angles.
It is master of colonisation. Can grow on almost any surface. Rock. Sand. Mud. Shell. Plastic. Metal. Tolerates wide range of salinities. From fresh water to full-strength sea water. Grows in bright sun or deep shade. It is weed of underwater world. Grows where others cannot. Turns bare surfaces into green carpets in weeks.
Biologically, it reproduces by fragmentation. Piece broken off by wave can grow into whole new plant. Also reproduces by releasing spores and simple cell division. This is why it appears so quickly in new area. Single fragment can colonise whole rock pool within weeks. It is alga of quick spread. Never misses opportunity.
To find hair algae is to find green slime on rock. Looks like wet hair. Feels like wet silk. Clings to everything it touches. Not beautiful. Not dramatic. Just there. Covering rocks. Growing in sun. Being hairy. It is alga of rock pool. One most people ignore. Proves most successful organisms are not always most glamorous. No one told it otherwise.