Marine life

General characteristics of a large marine ecosystem (Gulf of Alaska)

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.

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Percula Clownfish in a zoo

The Clownfish, or Anemonefish, are the subfamily Amphiprioninae of the family Pomacentridae. There are currently 27 species, of which one is in the genus premnas and the rest are in the subfamily's type genus Amphiprion. The other pomacentrids are called damselfish.

Clownfish are native to wide ranges of the warm waters of the Pacific; some species ranges overlap others. Clownfish are not found in the Atlantic Ocean. Clownfish live in a mutual relationship with sea anemones, or in some case settle in some varieties of soft corals, or large polyp stony corals. Once an anemone or coral has been adopted, the clownfish will defend it vigorously.

However, clownfish in an aquarium environment can exist very well without an anemone (this may be advisable as most anemones are extremely difficult to keep alive even for experienced aquarists). The anemone is required in nature because reef life is dangerous for small, brightly coloured fish with very poor swimming abilities; in an aquarium lacking predators it is not needed. For this reason, clownfish never stray far from their host. In an aquarium, where they don't have to forage for food, it is very common for clownfish to remain within 6–12 inches of their host for an entire lifetime.

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Sir John Murray, 1902

Sir John Murray (March 3, 1841–March 16, 1914) was a pioneering Scots-Canadian oceanographer and marine biologist.

Murray was born on 3 March 1841, at Cobourg, Ontario, Canada, to Scottish parents who had emigrated seven years earlier. He returned to Scotland to study, firstly at Stirling High School, and then at the University of Edinburgh, but soon left to join a whaling expedition to Spitsbergen as ships' surgeon in 1868.

He returned to Edinburgh to complete his studies in geology under Sir Archibald Geikie and natural philosophy under Peter Guthrie Tait. Tait introduced Murray to Charles Wyville Thomson who had been appointed to lead the Challenger Expedition. In 1872, Murray joined Wyville Thomson as his assistant on this four-year expedition to explore the deep oceans of the globe. After Wyville Thompson succumbed to the stress of publishing the reports of the Challenger Expedition, Murray took over, and edited and published over 50 volumes of reports, which were completed in 1896. He was knighted (K.C.B) in 1898. Murray was killed when his car overturned near his home on March 16 1914 at Kirkliston, Edinburgh, and he is buried at the nearby Dean Kirkyard.

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Did you know...

Light microscopy image of the undescribed species of Spinoloricus that is living in anoxic environment (Stained with Rose Bengal). Scale bar is 50 μm.
Titan triggerfish.jpg
  • Triggerfishes are the brightly coloured fishes of the family Balistidae. (pictured)
  • The sea otter often keeps a stone tool in its armpit pouch.

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Phalacrocorax-auritus-007.jpg
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.

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Marine Life Categories

Major Fields of Marine Biology: Marine Biology - Ecology - Zoology - Animal Taxonomy

Specific Fields of Marine Biology: Herpetology - Ichthyology - Planktology - Ornithology

Biologists: Zoologists - Algologists - Malacologists - Conchologists - Biologists - Marine Biologists - Anatomists - Botanists - Ecologists - Ichthyologists

Organisms:

Plants: Algae - Brown Algae - Green Algae - Red Algae - Sea Vegetables -

Invertebrates: Cnidarians - Echinoderms - Molluscs - Bivalves - Cephalopods - Gastropods

Fish: Fish - Bony fish - Lobe-finned fish - Ray-finned fish - Cartilaginous fish - Electric fish - Fish diseases - Rays - Sharks - Extinct fish - Fictional fish - Fisheries science - Fishing - Fishkeeping - Live-bearing fish

Reptiles and Amphibians: Marine reptiles - Sea turtles - Mosasaurs - Sauropterygia

Mammals: Marine mammals - Cetaceans - Pinnipeds - Sirenians

Miscellaneous: Aquaria - Oceanaria - Agnatha - Endangered species - Aquatic biomes - Biogeographic realms - Aquatic organisms - Cyanobacteria - Dinoflaggellates

Marine Life Topics

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