Marine plants are enormously important to the Great Barrier Reef, specifically algae, without which the coral reefs would not exist. Algae provide the food, building blocks and fortifications, while on the other hand seaweeds can also smother and cause reef degradation.
There are about 600 species of algae in the seas surrounding Queensland, most of them microscopic. While land plants belong to one major group, or division, algae belong to nine or more. There are 14 species of seagrasses in Australia, two of them found only here. Seagrasses appeared on earth about 70 million years ago whereas algae have been around for at least 2 billion years.
Many of the algae are not immediately recognisable as plants. Some of the coralline red algae grow as pink film over dead coral and other surfaces, laying down a strong cement of limestone as they grow. Coralline algae are responsible for holding the reef together, and add slowly to its structure. Without them, the reef would remain a heap of broken coral fragments.
Like almost all plants, algae capture light energy and, using a process called photosynthesis, convert carbon dioxide and water into food. Thus, directly or indirectly, algae feed many creatures of the reef including corals, clams, sponges, and other creatures. Seagrass and Mangroves also contribute plant matter to the reef system.
