Marine food web

The feeding relationships in an ecosystem consist of many food chains interconnected into a network called a food web.

Covering seventy-one percent of the Earth’s surface, the ocean provides us with a magnificent variety of creatures. Each of these creatures occupies a unique position on the food web, or trophic web, which is composed of producers, consumers, and decomposers. Organisms in a community are linked through what they eat and what eats them. A food chain is a single pathway connecting a producer with several levels of consumers. In a typical marine food chain, dinoflagellates convert energy from sunlight into food through photosynthesis and store it in their tissues. Copepods feed on dinoflagellates and incorporate this energy into their own tissues. The energy is transferred to sunfish when they feed on copepods, to small sharks that feed on sunfish, and to large sharks that feed on small sharks. 

For an environment to remain healthy, the food chain must remain unbroken. If one link in the chain is broken, all creatures on the chain may be endangered.

Producers

Photosynthetic organisms,(make their own food) like seaweed, zooxanthellae (algae living in coral tissue), and turf algae, make up this group.

Primary Consumers

Mostly Herbivores; snacking on producers. Sea urchins, some crab species, sponges, and even the large green sea turtle are primary consumers. The surgeonfish, a member of this group, mows down the turf algae to a healthy level.

Secondary Consumers

Dining on primary consumers, these animals are carnivorous. Goatfish and wrasses eat everything from snails and worms to crustaceans. This group also includes many species of coral eaters such as butterflyfish, filefish, triggerfish, and damselfish. Their specialized, elongated mouths enable them to chow down on the tiny individual polyps of the coral. 

Tertiary Consumers

These are the large fish that excite divers! Barracuda, groupers, snappers, and, of course, sharks, moray eels and dolphins are at the top of the food chain. Their feast includes other fish, crustaceans, and even octopi. At-risk reefs have low numbers of these top-level (apex) predators. They help to keep other fish populations at bay. Considering that tertiary consumers are commercially fished, their absence is a possibility and even a reality in many regions.

Decomposers

The little-glorified job of decomposing Dead Sea animals and plants is left to bacteria. Animal and plant wastes are converted to a food form subsequently used by animals throughout the food chain.

In addition, there are many inmates who eat the members of their own group too. But, this is actually not the end of food chain. The topmost predators of sea are hunted in large numbers by humans. This has proved quite harmful to the marine ecosystem of some regions. Many laws have been formed to stop hunting these masters of oceans, but no little avail.