The Coral’s Ecological Roles

Corals can obtain food through organic matter leaked by zooxanthellae, prey that have been stung, and absorbing dissolved organic compounds across the body wall. With 3 different ways of getting nutrients, corals assume the ecological roles of primary producer, primary consumer, carnivore, and detritus feeder.

Primary producer - This is the first trophic level of the ecosystem, where the primary producer provides the food for the rest of the following levels.

Primary consumer - This trophic level immediately follows the primary producers. They are made up of herbivore organisms that feed off plants and algae (the primary producers). They provide energy to the carnivores(secondary consumers) in the next trophic level.

Carnivore - This trophic level are secondary consumers that feed on the herbivore organisms, the primary consumers, one tropic level down.

Detritus feeder/detritivores- These are organisms that live on the refuse of the community, which include dead animals and feces. They are sometimes type of consumer that feeds off the dead. They may be found at several different levels in a food web.

This complex food web corals have reduces their dependence on a single food source. This is very good for coral survival in the event of environmental changes.

The System Within the Reef

It is probable that an efficient internal cycling exists in the reef ecosystem that could explain the rich biological processes in the poor nutrient tropical surface waters. Unfortunately, little is known of the cycling system. Nitrogen is believed to be the limiting nutrient in the ocean and in coral reefs. A lot of nitrogen from the atmosphere is dissolved in seawater and fixed so as able to be used by filamentous blue-green algae. Nitrates also come from the oxidation of ammonia by bacteria in the sediments of the reef lagoon during decomposition of organic matter. The oxidation of ammonia to nitrate is intensive in the fine-grained organic sediments that are trapped by sea-grass bed roots.

The Atlantic, Caribbean, and Indo-Indian coral reefs are the same in structural forms, habitats and species interaction, although the specific organisms occupying ecological roles vary between both oceans and individual reefs. The significant difference between the Pacific and Caribbean is that the Pacific’s corals only grows down to 60 meters whereas the Caribbean’s grows down to 100 meters.

The Pacific coral reefs have slower growth rates. The reasons for its sluggish growth will be explained in the section “Destruction of Coral Reefs.”

Notes on the Virtues of Field Experience

It is important to not focus on so few components so as to overlook the less noticeable organisms. The variety of organisms has produced different ways of life in order to survive. For example, Jeremy Jackson and his students at John Hopkins University showed that encrusting organisms have specific toxins for defensive and offensive purposes. As a matter of fact, corals that grow close together compete and can extrude mesenterial filaments from the gut to compete with other types of species. Judith Lang’s work in Discovery Bay showed that corals have a hierarchy of aggression. In this hierarchy, slow-growing, but aggressive, corals can avoid being overgrown by fast-growing, but less aggressive corals, create greater diversity overall. Of course, this is not always the case. James Porter has found that the dominant coral in reefs on the Pacific Panama coast is Pocillopora damicornis, which is both fast growing and aggressive.

Corals that grow together also exhibit many properties that are similar to those found in rainforests.