Portal:Marine life

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A male whale shark at the Georgia Aquarium.

The Marine Life Portal

Killer whales (orcas) are highly visible marine apex predators that hunt many large species. But most biological activity in the ocean takes place with microscopic marine organisms that cannot be seen individually with the naked eye, such as marine bacteria and phytoplankton.

Marine life, sea life, or ocean life is the plants, animals, and other organisms that live in the salt water of seas or oceans, or the brackish water of coastal estuaries. At a fundamental level, marine life affects the nature of the planet. Marine organisms, mostly microorganisms, produce oxygen and sequester carbon. Marine life, in part, shape and protect shorelines, and some marine organisms even help create new land (e.g. coral building reefs).

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 (e.g. dolphins, whales, otters, and seals) need to surface periodically to breathe air. (Full article...)


Marine biology is the scientific study of the biology of marine life, organisms in the sea. Given that in biology many phyla, families and genera have some species that live in the sea and others that live on land, marine biology classifies species based on the environment rather than on taxonomy. (Full article...)

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Cnidaria (/nɪˈdɛəriə, n-/ nih-DAIR-ee-ə, NY-) is a phylum under kingdom Animalia containing over 11,000 species of aquatic animals found both in fresh water and marine environments (predominantly the latter), including jellyfish, hydroids, sea anemones, corals and some of the smallest marine parasites. Their distinguishing features are a decentralized nervous system distributed throughout a gelatinous body and the presence of cnidocytes or cnidoblasts, specialized cells with ejectable flagella used mainly for envenomation and capturing prey. Their bodies consist of mesoglea, a non-living, jelly-like substance, sandwiched between two layers of epithelium that are mostly one cell thick. Cnidarians are also some of the only animals that can reproduce both sexually and asexually.

Cnidarians mostly have two basic body forms: swimming medusae and sessile polyps, both of which are radially symmetrical with mouths surrounded by tentacles that bear cnidocytes, which are specialized stinging cells used to capture prey. Both forms have a single orifice and body cavity that are used for digestion and respiration. Many cnidarian species produce colonies that are single organisms composed of medusa-like or polyp-like zooids, or both (hence they are trimorphic). Cnidarians' activities are coordinated by a decentralized nerve net and simple receptors. Cnidarians also have rhopalia, which are involved in gravity sensing and sometimes chemoreception. Several free-swimming species of Cubozoa and Scyphozoa possess balance-sensing statocysts, and some have simple eyes. Not all cnidarians reproduce sexually, but many species have complex life cycles of asexual polyp stages and sexual medusae stages. Some, however, omit either the polyp or the medusa stage, and the parasitic classes evolved to have neither form. (Full article...)

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A chemoautotrophic whale fall community in the Santa Cruz basin off southern California at a depth of 1,674 m (5,492 ft), including bacteria mats, vesicomyid clams in the sediments, galatheid crabs, polynoids, and a variety of other invertebrates.

A whale fall occurs when the carcass of a whale has fallen onto the ocean floor, typically at a depth greater than 1,000 m (3,300 ft), putting them in the bathyal or abyssal zones. On the sea floor, these carcasses can create complex localized ecosystems that supply sustenance to deep-sea organisms for decades. In some circumstances, particularly in cases with lower water temperatures, they can be found at much shallower depths, with at least one natural instance recorded at 150 m (500 ft) and multiple experimental instances in the range of 30-382 m (100-1300 ft). Whale falls were first observed in the late 1970s with the development of deep-sea robotic exploration. Since then, several natural and experimental whale falls have been monitored through the use of observations from submersibles and remotely operated underwater vehicles (ROVs) in order to understand patterns of ecological succession on the deep seafloor.

Deep sea whale falls are thought to be hotspots of adaptive radiation for specialized fauna. Organisms that have been observed at deep-sea whale fall sites include chordates, arthropods, cnidarians, echinoderms, mollusks, nematodes, and annelids. New species have been discovered, including some potentially specializing in whale falls. It has been postulated that whale falls generate biodiversity by providing evolutionary stepping stones for multiple lineages to move and adapt to new environmentally-challenging habitats. Researchers estimate that 690,000 carcasses/skeletons of the nine largest whale species are in one of the four stages of succession at any one time. This estimate implies an average spacing of 12 km (7.5 mi) and as little as 5 km (3.1 mi) along migration routes. They hypothesize that this distance is short enough to allow larvae to disperse/migrate from one to another. (Full article...)
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  • ... the open mouth of an adult southern right whale can be two metres wide!
  • ... when southern right whale and humpback whales breach (leap out of the water), seagulls can often be seen darting in to pick up pieces of skin that become dislodged from the breaching whales. Presumably this is an easy source of food for seagulls.
  • ... The insides of the sharks intestines are spiral shaped. Because of this, some sharks have spiral-shaped droppings.
  • ... whale and dolphin mothers ‘suckle’ their young underwater! Mothers have muscular mammary glands and ‘squirt’ their milk into the calf’s mouth, to ensure that the calf takes in as much of the energy rich milk as possible.
  • ... The sea otter often keeps a stone tool in its armpit pouch.
  • ... Until the late 16th century sharks were usually referred to in the English language as sea-dogs. The name "Shark" first came into use around the late 1560s to refer to the large sharks of the Caribbean Sea.

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Cuttlefish use camouflage to hide from predators.
Cuttlefish use camouflage to hide from predators.
Photo credit: Raul654

Cuttlefish are sometimes called the chameleon of the sea because of their remarkable ability to rapidly alter their skin colour at will. Their skin flashes a fast-changing pattern as communication to other cuttlefish and to camouflage them from predators.

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