Tidepools along the Pacific Coast, and throughout the world, are painted with the vivid pink of coralline algae. This plantlike organism that harnesses the sun’s power through photosynthesis encrusts rocks in thin sheets that resemble lichen; it also forms structures that branch like tiny trees, as in this photo. Both forms of pink coralline algae are hard to the touch because the organism is calcified, similar to coral. By cementing stony chunks of coral together, pink coralline algae plays a vital role in building coral reefs. It is the unsung mason of the world’s great reef constructions.
Tidepools in the Pacific Northwest lack coral reefs, but pink coralline algae is in bright abundance. This colorful algae covers rocks and reaches toward the sun with jointed branches. Limpets and chitons (both creatures are mollusks related to snails) graze on the pink crusts and eat the miniature forests of stony pink trees. Sea urchins also feast on the hallucinatory pink gardens at the ocean’s edge.
The flowerlike creature in this photo is a sea anemone, a carnivorous predator related to jellyfish and coral. Microscopic algae that live in the anemone’s tissue give the animal its bright hues. Corals, too, derive their vivid colors from the algae that live in their bodies. Algae are the unknown artists that paint the world’s oceans.