Marine life, or sea life or ocean life, is the plants, animals and other organisms that live in the salt water of the sea or ocean, or the brackish water of coastal estuaries. At a fundamental level, marine life affects the nature of the planet. Marine organisms produce oxygen and sequester carbon. Shorelines are in part shaped and protected by marine life, and some marine organisms even help create new land. The term marine comes from the Latin mare, meaning sea or ocean.
Most life forms evolved initially in marine habitats. By volume, oceans provide about 90 percent of the living space on the planet. The earliest vertebrates appeared in the form of fish, which live exclusively in water. Some of these evolved into amphibians which spend portions of their lives in water and portions on land. Other fish evolved into land mammals and subsequently returned to the ocean as seals, dolphins or whales. Plant forms such as kelp and algae grow in the water and are the basis for some underwater ecosystems. Plankton forms the general foundation of the ocean food chain, particularly the phytoplankton which are key primary producers.
Marine invertebrates exhibit a wide range of modifications to survive in poorly oxygenated waters, including breathing tubes as in mollusc siphons. Fish have gills instead of lungs, although some species of fish, such as the lungfish, have both. Marine mammals, such as dolphins, whales, otters, and seals need to surface periodically to breathe air.
A total of 230,000 documented marine species exist with some two million marine species yet to be documented. Marine species range in size from the microscopic, including phytoplankton which can be as small as 0.02 micrometres, to huge cetaceans (whales, dolphins and porpoises), including the blue whale – the largest known animal reaching 33 metres (108 ft) in length. Marine microorganisms, including protists, bacteria and viruses, constitute about 70% of the total marine biomass.
Albatrosses, of the biological family Diomedeidae, are large seabirds allied to the procellariids, storm petrels and diving petrels in the order Procellariiformes (the tubenoses). They range widely in the Southern Ocean and the North Pacific. They are absent from the North Atlantic, although fossil remains show they once occurred there too. Albatrosses are amongst the largest of flying birds, and the great albatrosses (genus Diomedea) have the largest wingspans of any extant birds. The albatrosses are usually regarded as falling into four genera, but there is disagreement over the number of species.
Albatrosses are highly efficient in the air, using dynamic soaring and slope soaring to cover great distances with little exertion. They feed on squid, fish and krill by either scavenging, surface seizing or diving. Albatrosses are colonial, nesting for the most part on remote oceanic islands, often with several species nesting together. Pair bonds between males and females form over several years, with the use of ritualised dances, and will last for the life of the pair. A breeding season can take over a year from laying to fledging, with a single egg laid in each breeding attempt.
More on the Albatross
Rachel Louise Carson (27 May 1907 – 14 April 1964) was a Pittsburgh-born zoologist and marine biologist whose landmark book, Silent Spring, is often credited with having launched the global environmental movement. Silent Spring had an immense effect in the United States, where it spurred a reversal in national pesticide policy.
Rachel Carson was born in 1907 on a small family farm near Springdale. As a child, she spent many hours learning about ponds, fields, and forests from her mother. She originally went to school to study English and creative writing, but switched her major to marine biology. Her talent for writing would help her in her new field, as she resolved to "make animals in the woods or waters, where they live, as alive to others as they are to me". She graduated from the Pennsylvania College for Women, today known as Chatham College, in 1929 with magna cum laude honors. Despite financial difficulties, she continued her studies in zoology and genetics at Johns Hopkins University, earning a master's degree in zoology in 1932.
More on Rachel Carson
Did you know...
- Triggerfishes are the brightly coloured fishes of the family Balistidae. (pictured)
- The sea otter often keeps a stone tool in its armpit pouch.
Things you can do
Photo credit: Mdf
The Double-crested Cormorant (Phalacrocorax auritus) is a North American member of the cormorant family of seabirds. Its name is derived from the Greek words phalakros (bald) and kora (raven), and the Latin auritus (eared). Folk names of this bird include Crow-duck, Farallon Cormorant, Florida Cormorant, lawyer, shag, and Taunton turkey.
More on the Double-crested Cormorant
Marine Life Categories
Marine Life Topics