Predation includes any interaction between two species in which one species benefits by obtaining resources from and to the detriment of the other. While it's most often associated with the classic predator-prey interaction, in which one species kills and consumes another, not all predation interactions result in the death of one organism. In the case of herbivory, a herbivore often consumes only part of the plant.
Real Life Examples
Coral predators include some types of marine snails and marine slugs, known as nudibranchs. Interestingly, these coral predators digest the animal tissue and release the symbiotic algae (zooxanthellae) in their feces. The nudibranchs may also keep the symbiotic algae for their own nutritional use.
Competition exists when multiple organisms vie for the same, limiting resource. Because the use of a limited resource by one species decreases availability to the other, competition lowers the fitness of both.
real life examples
When competition is between the same species, it is referred to as intraspecies competition. For example, there may be spatial competition among the elkhorn coral species.
When competition is between different species, like a snail and a starfish competing to eat coral, it is referred to as interspecies competition.
Parasitism, relationship between two species of plants or animals in which one benefits at the expense of the other, commonly without killing the host organism
Real Life Example
One of the most common parasites of corals is the Pacific Ocean’s Crown of Thorns Sea Star. This is a parasitic relationship in that the sea stars find food in the polyps of the coral whereas the coral is stripped down to its skeleton and left to die.
It is estimated that a single Crown of Thorns Sea Star can eat from 2 to 6 square meters of coral per year.
Secondly, Christmas Tree Worms actually bore into the skeleton of the coral, damaging it in search of food and protection. This is another example of a parasitic symbiotic relationship on coral reef.
Mutualism describes an interaction that benefits both species.
Real Life Example
Shallow water, reef-building corals have a symbiotic relationship with photosynthetic algae called zooxanthellae, which live in their tissues. The coral provides a protected environment and carbon dioxide that zooxanthellae need for photosynthesis. In return, zooxanthellae take in carbon dioxide and give off oxygen and other important nutrients that are then used by the host polyp.
Furthermore, the presence of the pigments inside the zooxanthellae also help protect the coral's white skeleton from sunlight. This is a mutual symbiotic relationship that is beneficial to both participants.
Ever wondered how the sea anemones in “Finding Nemo” protected Nemo and his family? The sea anemone and clownfish showcase a great example of mutualistic symbiosis. The anemone protects the clownfish by concealing it within its poisonous arms (which the clownfish is immune to). The anemone also leaves scraps of its meals for the clownfish to consume.
In return, the clownfish rids the anemone of parasites, wards away predators, and even offers nutrients by way of its excrement. (5 Symbiotic Relationships in the Ocean, n.d.)
An interaction where one species benefits and the other remains unaffected is known as commensalism.
Real Life Examples
The relationship between imperial shrimp and the sea cucumber is a good example of commensalism—one benefits while the other neither benefits nor is harmed.
The imperial shrimp first finds a sea cucumber. It will then utilize the sea cucumber for its locomotive purposes by hanging tight as they move through waters filled with the shrimp’s food source. The shrimp will only disembark to hunt (until it runs out of food) and then climb back aboard to travel to the next feeding ground.
In some cases, their relationship may turn into a mutualistic one—particularly with cleaner shrimp. The latter may clean algae and parasites from the sea cucumber as “payment” for the free ride.
Mutualism is also seen between sponges and small marine creatures. Sponges are longtime inhabitants of coral reefs. These sessile, or stationary, organisms provide shelter for fish shrimp, crabs and other small animals.