Brown Algae

A few species of brown algae live on the reef. Some are small and grow inconspicuously next to the corals, while others are prominent on the reef flat. Like many red algae, browns have complex life cycles that involve alternation of sexual and asexual generations.

Brown algae vary in form from encrusting growths to thin filaments, fleshy stalks, and giant kelps that reach sizes of 328 feet (100 m) long. Most brown algae cling to the bottom with holdfasts. Exceptions are the encrusting forms and a type referred to as sargassum, which floats on inshore reef waters.

Turbinaria is a reef brown alga that has a tough, spiny thallus capable of deterring would-be grazers. Padina, a fanshaped brown alga, contributes to reef building. On the outer surface of its thallus, it forms bands of calcium carbonate that helps cement the reef together.