The Classification of Organisms in the Ocean

The taxonomy or classification of species was developed by Carl Linnaeus in the 1700s. It is still used today by biologists. Taxonomy helps in understanding the relationship among species. It also helps one to understand and predict the alteration of ecosystems by natural forces (earthquakes, volcanic activity, etc.) and human factors (overfishing, pollution, etc.)

The following are overview classifications of organisms that live in the sea.

I. Phytoplankton – Plant Kingdom

This is the beginning and essential component of the marine food chain. Algae (seaweed) belongs to phytoplankton. Phytoplankton is single-celled plants that support many ocean species. They are crucial for providing carbon in the atmosphere.

A. Larger species in Phytoplankton: Diatoms and Dinoflagellates.

B. Smaller species are nonoplankton and picoplankton.

II. Coral Reefs

Coral reefs provide shelter for many ocean creatures. They create sand for beaches and act as buffers for animals near the shoreline. Coral polyps make the reefs. These are small colonial animals that look like an upside-down jellyfish. These polyps are able to take excess carbon dioxide in the water and turn it into limestone.

III. Zooplankton

Zooplankton breaks down into two categories, size and stages of development.


A. Picoplankton – measures less that 2 micrometers

B. Nonoplankton – 2-20 micrometers

C. Microplankton – 200 millimeters (8 inches).

Stages of Development

A. Meroplankton – larvae that turn into worms, mollusks, crustaceans, coral echinoderms, fishes.

B. Holoplankton stay plankton for their entire life cycle.

IV. Invertebrates

Animals that lack backbones are invertebrates. Some use shells (hermit crab) for protection. Included are sponges, cnidarians (jellyfish), worms, mollusks.

V. Vertebrates – belong to the Kingdom Animalia

A. Vertebrates are structurally complex organisms. The are seven classes in vertebra: agnatha (lampreys and hagfish). Reptalia is sea turtles, terrapins and tortoises, snakes iguana and sea water crocodile. Aves are aquatic birds and include penguins. Cormorants, pelicans, flamingos and birds that fly close to the ocean surface, Black skimmers.

B. Vertebrate Mammals

Mammals have evolved and adapted over time to become the mammals they are today.

C. Species: Otters, Polar Bears (semi-aquatic), Pinnipeds (seals), Sirenians (manatees and dugong – vegetarians)

Cetaceans have two types: Toothed whales – sperm whales, beaked whales and dolphins. Baleen Whales have two blowholes and feed on plankton.

Marine organisms begin at the lowest level of plants (plankton) that start the cycle of life to the evolved mammals. It is a stepping stone to making marine life real to those who do not observe these organisms first-hand. Marine life is vital for all peoples well being. The world must recognize the importance of maintaining and strengthening marine habitats.