fan weed with delicate fan-shaped fronds in the surge zone
- Size
- Height: 10–20 cm
- Lifespan
- 2–5 years
- Diet
- Grows on rocky reefs in low intertidal and shallow subtidal zones of clear, sheltered waters. Requires clean water, stable rock surfaces, and good water flow. Tolerates sun, moderate wave action, and temperature fluctuations.
- Habitat
- Grows on rocky reefs throughout New Zealand, from the Three Kings Islands down to Stewart Island, in the low intertidal and shallow subtidal zones. A creature of the clear water, the sun-dappled reefs, the places where the light filters through and the current flows gently. Forms fan-shaped, layered fronds that look like a deck of cards spread out underwater.
- Range
- Found throughout the North and South Islands on rocky reefs in low intertidal and shallow subtidal zones of clear, sheltered waters. Most common on the North Island's east coast and the South Island's northern coast. Also found in Australia and South America.
- Endemism
- Native
- Main Threats
- None significant. This species is common and widespread in clear, sheltered waters. Localised threats include coastal development, pollution, sedimentation from land clearance, and climate change affecting water temperature and clarity.
- Population
- Not Threatened. Fan weed is common on rocky reefs throughout New Zealand, particularly in clear, sheltered waters. It often grows on vertical rock faces and under overhangs.
- Conservation Status
- Not Threatened
The one that looks like a hand fan. A seaweed that is a deck of cards.
The fronds are flattened, broad, and fan-shaped, a semicircle of golden-brown tissue, sometimes split into several lobes. The surface is marked with concentric bands of darker and lighter tissue, like the growth rings of a tree or the layers of a deck of cards. It is stiff and leathery, holding its shape in the current, refusing to be bent by the flow of water. A seaweed that is stiff.
What makes it special is the layering. The fan weed grows in overlapping tiers, one frond above another, like a stack of fans. The fronds are attached to the rock by a small, disc-like holdfast, and they branch repeatedly, creating a dense, layered canopy. It is the deck of cards of the underwater world, a city of golden-brown layers.
The fan weed is a brown alga, a member of the Dictyotaceae family. It reproduces by releasing spores from specialised structures on the surface of its fronds. The spores are produced in dark spots that are visible on the surface of the fan, tiny dots that mark the sites of reproduction.
The fan weed provides habitat for small invertebrates. Tiny crustaceans hide among its fronds. Small snails graze on its surface. Its layered structure creates a complex, three-dimensional habitat, a city of small spaces, a refuge for the small and the vulnerable.
To find fan weed is to find a golden-brown fan on the rock. The rocky reef is underwater. The fan weed grows in overlapping tiers, golden-brown, stiff and leathery, bands of light and dark. A tiny crustacean hides among its fronds. The fan weed does not know it is a city. It does not know it is a deck of cards.
It just wants to hold its shape in the current. The layered one, the fan-shaped one, the one that proves that the sea loves geometry as much as the land. The fan weed is proof.