Last week Daedalus proposed a ship coated with ice. Not only would it have the lowest possible skin-friction; fouling organisms could never grow on its hull. He now doubts this latter assertion. No marine plant is known to anchor itself to ice. But many specialized bacteria can live in ice, and tundra lichens can survive in an environment dominated by it. So perhaps a seaweed exists, or can be bred, to flourish on an icy surface.

Many seaweeds anchor themselves to solid surfaces, both naval and natural. They do so, not to draw nourishment from the surface, but to contact a large volume of water as it sweeps past their anchorage. A seaweed that could fasten itself to ice would gain the same benefit. DREADCO biologists are now trying to create one.

The trouble, of course, is that natural ice is usually melting. No plant can stick to its surface; it needs to carve out a cavity. Daedalus recalls that Arctic fish, like many other cold-adapted species, generate high internal concentrations of special anti-freeze compounds. If the genes for such a compound could be transferred to seaweed, and the plant could learn to exude it from its anchoring foot, it could melt out a secure root-cavity in the ice. As fast as the ice melted, it would deepen and renew its cavity. It could spread as a permanent coating on the submerged surface of an ice shelf, even colonizing the underneath. Enough light would penetrate the ice to sustain photosynthesis.

This challenging biological project has a bold ecological purpose — to reduce the melt-rate of the polar ice. During the Second World War, an artificial iceberg was proposed as an aircraft-carrier. To reduce its melt-rate, it was to be made from a dilute suspension of wood-pulp in water. This would give it a furry surface, which would be an excellent thermal insulator. Similarly, the Arctic and Antarctic polar ice shelves could be insulated by seeding them with Daedalus's ice-weed.

A menace of global warming would thus be countered. Released in the polar oceans, ice-weed would spread luxuriantly under the polar ice shelves and submarine glaciers, reducing their rate of melting. Their contribution to the rising sea-level would be cut right back. They would also release fewer free-floating icebergs to menace the world's shipping lanes. The bergs that were released would, of course, be thoroughly weed-insulated, and would last much longer. They might even be captured and towed into tropical ports for use as sources of fresh water.