Commercial ships of a nation, whether privately or publicly owned, and the personnel who operate such ships, as distinct from the personnel of naval vessels. Merchant ships are used to transport people, raw materials, and manufactured goods. Merchant fleets can be important economic assets for nations with limited natural resources or a small industrial base. By carrying the commerce of other nations on the seas, a merchant fleet contributes to its home nation's foreign-exchange earnings, promotes trade, and provides employment. The U.S. Merchant Marine Academy (founded 1943) is in Kings Point, N.Y.
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Any of about 5,400 species of marine worms of the annelid class Polychaeta, having a segmented body with many setae (bristles) on each segment. Species, often brightly coloured, range from less than 1 in. (2.5 cm) to about 10 ft (3 m) long. Most body segments bear two bristly parapodia (lobelike outgrowths). The head has short sensory projections and tentacles. Adults may be free-swimming or sedentary; larvae are free-swimming. Found worldwide, polychaetes are important for turning over sediment on the ocean bottom. One species, the bloodworm, is a popular saltwater fish bait. Seealso tube worm.
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Any deposit of insoluble material, primarily rock and soil particles, transported from land areas to the ocean by wind, ice, and rivers, as well as the remains of marine organisms, products of submarine volcanic activity, and chemical precipitates from seawater that accumulate on the seafloor.
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Scientific discipline concerned with all aspects of the world's oceans and seas, including their physical and chemical properties, origin and geology, and life forms. Research entails sampling seawater and marine life, remote sensing of oceanic processes with aircraft and satellites, and exploration of the seafloor. Oceanography aids in predicting weather and climate, in exploitation of the Earth's resources, and in understanding the effects of pollutants. Seealso marine geology.
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Scientific discipline concerned with all geologic aspects of the continental shelves and slopes and the ocean basins. Marine geology originally focused on marine sedimentation and the interpretation of bottom samples. The advent of the concept of seafloor spreading, however, broadened its scope. Many investigations of the oceanic ridge system, the magnetism of rocks on the seafloor, geochemical analyses of deep brine pools, and seafloor spreading and continental drift may be considered within the general realm of marine geology.
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Dense aquatic accumulation of microscopic organisms produced by an abundance of nutrients in surface water coupled with adequate sunlight for photosynthesis. The microorganisms or the toxic substances they release may discolour the water, exhaust its oxygen content, poison aquatic animals and waterfowl, and irritate the skin and respiratory tract of humans. Single species of algae, diatoms, or dinoflagellates, reproducing every few hours, may dominate a bloom's population; the number of individuals per quart (litre) of water, normally about 1,000, can increase to 60 million. Blooms of the dinoflagellate genus Gymnodinium cause red tides. The Red Sea is named for the occasional blooms of the alga Trichodesmium erythraeum. Seealso water pollution.
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Science that deals with the animals and plants of the sea and estuaries and with airborne and terrestrial organisms that depend directly on bodies of saltwater for food and other necessities. Marine biologists study the relations between ocean phenomena and the distribution and adaptations of organisms. Of particular interest are adaptations to the chemical and physical properties of seawater, the movements and currents of the ocean, the availability of light at various depths, and the composition of the sea floor. Other important areas of study are marine food chains, the distribution of economically important fish and crustaceans, and the effects of pollution. In the later 19th century, the emphasis was on collecting and cataloging marine organisms, for which special nets, dredges, and trawls were developed. In the 20th century, improved diving equipment, submersible craft, and underwater cameras and television have made direct observation possible.
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Member of a military force trained for service at sea and in land operations related to naval campaigns. They existed as far back as the 5th century BC, when the Greek fleets were manned by epibatai, or heavily armed sea soldiers. In the Middle Ages ordinary soldiers were often assigned to shipboard duty; not until the naval wars of the 17th century was the distinct role of marines rediscovered almost simultaneously by the British and the Dutch, who raised the first two modern marine corps, the Royal Marine (1664) and the Koninklijke Nederlandse Corps Mariniers (1665). Seealso U.S. Marine Corps.
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