Coralline algae

Coralline algae are a special kind of red algae. They have hard, chalky parts in their cell walls, so they feel tough like rock. They are usually pink or red, but some can be purple, yellow, blue, white, or gray-green.

These algae grow on rocks and hard surfaces in shallow ocean areas, close to the water's edge and in coral reefs. They look like colorful patches on rocks. Some types grow in round balls or bumpy shapes.

Coralline algae are very important for ocean life. Many sea animals, like sea urchins, parrot fish, limpets, and chitons, eat them. In places such as the Mediterranean Sea, these algae help build special reefs called Coralligène, giving many sea creatures a home. There are over 1,600 known types of coralline algae. Most live in salty ocean water, but one kind can live in freshwater.

Description

Coralline algae come in two main forms. One form, called geniculate, looks like small, branching trees. They attach to rocks or other hard surfaces. The other form, nongeniculate, grows as thin to thick crusts on rocks, shells, or seagrasses. Some of these crusts can be leafy.

These algae grow very slowly, adding just a little each year. They all start with a crust-like stage. Their bodies have three layers.

Coralline algae contain calcium carbonate, and they can turn into fossils. They have been used as markers in studying rocks and were even used as building material in ancient Greece.

Evolutionary history

The fossil record of these special types of algae matches what scientists learn from their genes. We can find these algae in very old rocks from a time called the Ediacaran. True coralline algae appear in rocks from the Jurassic period and later.

These algae have a good fossil record starting from the Early Cretaceous period. Their fossils help scientists learn when different kinds of these algae first appeared. Some types of these algae change with ocean temperatures, while others are more common when certain fish, like parrotfish, are around.

Habitat

Coralline algae grow in all the world's oceans. They cover rocky surfaces where they live. These algae can survive in different water depths, from areas that are sometimes out of the water to depths of about 270 meters. Some types can live in water that is not very salty or even in freshwater, but most like salty water. They can also handle changes in water clarity and nutrient levels.

Biology

Thin layers of coralline algae cover fresh surfaces in the ocean. Over time, these layers can grow thicker or form branches. Sometimes, they break off and form small, round nodules called Rhodoliths. Coralline algae are found in many ocean areas, especially in colder places and the Mediterranean Sea. They can live in deep water because they can make their own food even in dim light.

Many coralline algae help certain baby sea creatures, like abalone, settle and grow. This helps both the algae and the baby animals. The algae also give tiny homes to small sea creatures, helping them stay safe. In coral reefs, coralline algae are important because they help build and strengthen the reef by adding calcium carbonate. They are especially important in areas with strong waves, where they help protect the coast by reducing erosion.

Relation to humans

The first coralline alga known as a living thing was probably Corallina in the 1st century AD. In 1837, Rodolfo Amando Philippi learned that coralline algae were not animals. He gave them the names Lithophyllum and Lithothamnion.

Because they are hard, coralline algae can be helpful. In Britain and France, people collect them to help make soil better.

Coralline algae are also used to make dental implants and as a food additive for farm animals. They are popular in home aquariums because they add color and help keep the water clean.