Reef Ecosystems

The coral reefs are extremely diverse habitats and can be viewed as the rainforest of the oceans. For example you can find as much as 2000 different fish-species on a single coral reef. The enormous number of different species of different animals, and the large heterogeneity of ecological niches in the coral reef makes it a difficult task to map the interactions between the different trophical levels not to mention interactions between animal species. Therefore the following text will mainly introduce some of the different animal groups that live in the coral reefs other than corals.

Coral Reef algae:
In short four forms of coral reef algae can be identified: 1) phytoplankton, 2) micro-filamentous algae (filamentous algae belonging to different classes (green algae, red algae and cyanobacteria)), 3) coralline algae (mainly red algae) and 4) macroalgae (red, brown and green algae).

The coral reef algae are found in various places in the coral reef, and no clear zonation exists in the distribution patterns of the different algae. This is mainly due to the spatial distribution of different habitats caused by a high heterogeneity in the physical habitat.

Algal growth is of cause limited by the lack of nutrients and light penetration/availability.

Coral reef herbivores:
A large number of different herbivores exist on the coral reef. Many of these are fish but some are sea urchins, mollusks and crustaceans. Some of these feed directly on the corals while others feed on the coral reef algae.

All though a large number of the coral reef herbivores do not feed directly on the corals, they play an important part in the ecosystem. They are necessary to control especially the macroalgae, who can overgrow the coral reefs if they are not grazed. If the macroalgae were allowed to spread the corals would die due to the diminished light-availability.

The coral reefs support a large number of fish-species some of these are herbivorous. The herbivorous fishes play an important role in controlling algae populations, but they also help redistribute the nutrients between various locations on the coral reef (nutrients are released through faces).

Coral reef predators:
The predators in the coral reef ecosystem are mainly teleost (bone-fish) and elasmobranch (sharks) fishes, crustaceans and carnivorous snails. While sharks feed exclusively on fishes and other large prey, some fishes feed directly on the coral polyps (example: the Parrotfish).