bubble weed with air-filled floats keeping it in the current

Size
Length: 10–30 cm
Lifespan
1–2 years
Diet
Photosynthetic. Absorbs dissolved nutrients from seawater. Requires clean water, stable rock surfaces, and good light for growth.
Habitat
Grows on rocky shores throughout New Zealand, from the Three Kings Islands down to Stewart Island, in the intertidal zone where the tide rises and falls. A creature of the splash zone, the rock pools, the places where the waves crash and the sun bakes the rocks at low tide. Forms tangled mats of bead-like chains.
Range
Found throughout the North and South Islands on rocky shores, particularly in the upper and mid-intertidal zone. Most common in rock pools and on exposed platforms. Also found in Australia and South America.
Endemism
Endemic
Main Threats
None significant. This species is one of the most common seaweeds on New Zealand's rocky shores. Localised threats include coastal development, pollution, rock pool disturbance, and climate change affecting intertidal conditions.
Population
Not Threatened. Bubble weed is one of the most common seaweeds on New Zealand's rocky shores, particularly in the upper and mid-intertidal zone. It is often the dominant seaweed in rock pools and on exposed platforms.
Conservation Status
Not Threatened
Human Risk
harmless
Handling Note
marine algae, safe to handle
Conservation Note
Endemic brown 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 bubble weed from other seaweeds. It was likely grouped with other brown seaweeds called rimu. The bubble weed was recognised as a sign of a healthy intertidal zone. A rock platform covered in bubble weed was a platform that was alive. A place where the small creatures of the tide could hide. The beads were sometimes used as toys. Children would collect the chains and pop the beads. Or string them into necklaces that would shrivel in the sun.
It wears floaties. Bubble weed looks like it is wearing floaties. It has fronds that are made of chains of small, round, air-filled beads. Like a string of green or brown pearls. Each bead is a hollow, watertight chamber. Filled with air. The beads are connected end to end. Forming branching chains that can be up to 20 centimetres long. The whole plant looks like a piece of seaweed that has swallowed a bunch of marbles. It is the alga of the bubbly surface. The one that floats on the tide. What makes it special is the bubbles. The air-filled beads keep the bubble weed afloat. Lifting its fronds up toward the light. They also act as shock absorbers. Protecting the plant from the pounding of the waves. When the tide goes out, the beads deflate slightly. And the plant collapses into a wet, squishy mat on the rocks. When the tide comes back in, the beads reinflate. And the plant floats back up. It is the alga of the tide cycle. The one that changes shape with the water. The bubble weed is a master of the intertidal zone. It can survive hours of exposure to the sun and the air at low tide. Its beads shrivelling but not dying. When the tide returns, it rehydrates within minutes. The beads swelling back to their full, bubbly size. It is a survivor of the edge. The place where the land meets the sea. The one that has learned to hold water in its beads. Biologically, the bubble weed is a brown alga. It reproduces by releasing spores from specialised structures on its beads. The spores are released during high tide. Carried away by the current. And settle on nearby rocks to grow into new plants. To walk across a rock platform at low tide is to walk on bubble weed. The beads squelch under your feet. Popping like bubble wrap. It is strange, wonderful, and slightly addictive. The bubble weed is the seaweed that looks like it is wearing floaties. The bubbly one. The squishy one. The one that pops when you step on it.