Marine Tumbleweeds

The ocean floor and the wind-swept prairies of the west have something in common: tumblin’ tumbleweeds. On the prairie, they’re nasty bushes teeming with sharp thorns. In the ocean, they’re growing clumps of red algae known as rhodoliths. They can tumble along with the currents until they get too heavy, when they settle down for good.

Rhodoliths are found in all the world’s oceans, from the tropics to the arctic. They often congregate in large, dense beds. They need sunlight to produce energy, so they’re most common in shallow coastal waters.

Many species of rhodolith begin with a small clump of algae around a hard nucleus, like a grain of sand or a bit of shell. They attract more algae, so they grow. Over time, they form hard skeletons, like corals-a process that takes carbon dioxide from the atmosphere, helping store carbon in the ocean.

They come in several shapes. But they all consist of solid knots or branches with open spaces between. That makes them important members of the marine ecosystem.

When they get big enough to settle down, they fill the same role as coral reefs. They offer protected spaces for fish, crabs, worms, and other species. That attracts other life, forming a busy ecosystem-and often creating productive fishing grounds.

Rhodolith beds help in other ways as well. They can stabilize the sediments close to shore and filter impurities from the water, for example non-thorny benefits from some tumblin’ tumbleweeds.

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