A body of water covering approximately one-fifth of the total ocean area of the earth, extending amidst Africa in the west, Australia in the east, Asia in the north, and Antarctica in the south. Including the Red Sea and the Persian Gulf, it constitutes the third largest ocean after the ATLANTIC OCEAN and the PACIFIC OCEAN. (New Encyclopaedia Britannica Micropaedia, 15th ed, 1990, p289)

Somewhat flattened, globular echinoderms, having thin, brittle shells of calcareous plates. They are useful models for studying FERTILIZATION and EMBRYO DEVELOPMENT.

The salinated water of OCEANS AND SEAS that provides habitat for marine organisms.

A great expanse of continuous bodies of salt water which together cover more than 70 percent of the earth's surface. Seas may be partially or entirely enclosed by land, and are smaller than the five oceans (Atlantic, Pacific, Indian, Arctic, and Antarctic).

The order Actiniaria, in the class ANTHOZOA, comprised of large, solitary polyps. All species are carnivorous.

The study of the origin, structure, development, growth, function, genetics, and reproduction of organisms which inhabit the OCEANS AND SEAS.

Free-floating minute organisms that are photosynthetic. The term is non-taxonomic and refers to a lifestyle (energy utilization and motility), rather than a particular type of organism. Most, but not all, are unicellular algae. Important groups include DIATOMS; DINOFLAGELLATES; CYANOBACTERIA; CHLOROPHYTA; HAPTOPHYTA; CRYPTOMONADS; and silicoflagellates.

A class of Echinodermata characterized by long, slender bodies.

The flow of water in enviromental bodies of water such as rivers, oceans, water supplies, aquariums, etc. It includes currents, tides, and waves.

The continent lying around the South Pole and the southern waters of the Atlantic, Pacific, and Indian Oceans. It includes the Falkland Islands Dependencies. (From Webster's New Geographical Dictionary, 1988, p55)

A functional system which includes the organisms of a natural community together with their environment. (McGraw Hill Dictionary of Scientific and Technical Terms, 4th ed)

The gaseous envelope surrounding a planet or similar body. (From Random House Unabridged Dictionary, 2d ed)

Community of tiny aquatic PLANTS and ANIMALS, and photosynthetic BACTERIA, that are either free-floating or suspended in the water, with little or no power of locomotion. They are divided into PHYTOPLANKTON and ZOOPLANKTON.

The Arctic Ocean and the lands in it and adjacent to it. It includes Point Barrow, Alaska, most of the Franklin District in Canada, two thirds of Greenland, Svalbard, Franz Josef Land, Lapland, Novaya Zemlya, and Northern Siberia. (Webster's New Geographical Dictionary, 1988, p66)

A thick mass of ICE formed over large regions of land; RIVERS; LAKES; ponds; or SEAWATER.

A mass of organic or inorganic solid fragmented material, or the solid fragment itself, that comes from the weathering of rock and is carried by, suspended in, or dropped by air, water, or ice. It refers also to a mass that is accumulated by any other natural agent and that forms in layers on the earth's surface, such as sand, gravel, silt, mud, fill, or loess. (McGraw-Hill Dictionary of Scientific and Technical Terms, 4th ed, p1689)

A genus of marine planktonic CYANOBACTERIA in the order PROCHLOROPHYTES. They lack PHYCOBILISOMES and contain divinyl CHLOROPHYLL, a and b.

The relationships of groups of organisms as reflected by their genetic makeup.

Organisms that live in water.

An order of pelagic, shrimplike CRUSTACEA. Many consume ZOOPLANKTON and a few are predacious. Many antarctic species, such as Euphausia superba, constitute the chief food of other animals.

Periodic movements of animals in response to seasonal changes or reproductive instinct. Hormonal changes are the trigger in at least some animals. Most migrations are made for reasons of climatic change, feeding, or breeding.

The inanimate matter of Earth, the structures and properties of this matter, and the processes that affect it.

An inland sea between Europe and Asia. It is connected with the Aegean Sea by the Bosporus, the Sea of Marmara, and the Dardanelles.

A class in the phylum CNIDARIA, comprised mostly of corals and anemones. All members occur only as polyps; the medusa stage is completely absent.

The variety of all native living organisms and their various forms and interrelationships.

The science dealing with the earth and its life, especially the description of land, sea, and air and the distribution of plant and animal life, including humanity and human industries with reference to the mutual relations of these elements. (From Webster, 3d ed)

The common name for the phylum of microscopic unicellular STRAMENOPILES. Most are aquatic, being found in fresh, brackish, and salt water. Diatoms are noted for the symmetry and sculpturing of their siliceous cell walls. They account for 40% of PHYTOPLANKTON, but not all diatoms are planktonic.

Places for cultivation and harvesting of fish, particularly in sea waters. (from McGraw-Hill Dictionary of Scientific and Technical Terms, 4th ed)

A group of cold-blooded, aquatic vertebrates having gills, fins, a cartilaginous or bony endoskeleton, and elongated bodies covered with scales.

The longterm manifestations of WEATHER. (McGraw-Hill Dictionary of Scientific and Technical Terms, 6th ed)

The presence of bacteria, viruses, and fungi in water. This term is not restricted to pathogenic organisms.

Increase in the temperature of the atmosphere near the Earth's surface and in the troposphere, which can contribute to changes in global climate patterns.

Hot springs on the ocean floor. They are commonly found near volcanically active places such as mid-oceanic ridges.

The motion of air relative to the earth's surface.

The collective name for the republics of ESTONIA; LATVIA; and LITHUANIA on the eastern shore of the Baltic Sea. (Webster's New Geographical Dictionary, 1988, p111)

Any significant change in measures of climate (such as temperature, precipitation, or wind) lasting for an extended period (decades or longer). It may result from natural factors such as changes in the sun's intensity, natural processes within the climate system such as changes in ocean circulation, or human activities.

The most diversified of all fish orders and the largest vertebrate order. It includes many of the commonly known fish such as porgies, croakers, sunfishes, dolphin fish, mackerels, TUNA, etc.

Carbonic acid calcium salt (CaCO3). An odorless, tasteless powder or crystal that occurs in nature. It is used therapeutically as a phosphate buffer in hemodialysis patients and as a calcium supplement.

Salts or ions of the theoretical carbonic acid, containing the radical CO2(3-). Carbonates are readily decomposed by acids. The carbonates of the alkali metals are water-soluble; all others are insoluble. (From Grant & Hackh's Chemical Dictionary, 5th ed)

A group of Indian Ocean Islands, the islands of Great Comoro, Anjouan, Mayotte, and Moheli, lying between northeast Mozambique and northwest Madagascar. The capital is Moroni. In 1914 they became a colony attached to Madagascar administratively and were made a French overseas territory in 1947. Except for Mayotte which remained French, Comoros became an independent republic in 1975. Comoros represents the Arabic qamar, moon, said by some scholars to be linked with the mystical Mountains of the Moon said to be somewhere in equatorial Africa. (From Webster's New Geographical Dictionary, 1988, p283 & Room, Brewer's Dictionary of Names, 1992, p122)

The cycle by which the element carbon is exchanged between organic matter and the earth's physical environment.

A phylum of the most familiar marine invertebrates. Its class Stelleroidea contains two subclasses, the Asteroidea (the STARFISH or sea stars) and the Ophiuroidea (the brittle stars, also called basket stars and serpent stars). There are 1500 described species of STARFISH found throughout the world. The second class, Echinoidea, contains about 950 species of SEA URCHINS, heart urchins, and sand dollars. A third class, Holothuroidea, comprises about 900 echinoderms known as SEA CUCUMBERS. Echinoderms are used extensively in biological research. (From Barnes, Invertebrate Zoology, 5th ed, pp773-826)

Minute free-floating animal organisms which live in practically all natural waters.

A class in the phylum MOLLUSCA comprised of SNAILS and slugs. The former have coiled external shells and the latter usually lack shells.

Constituent of 30S subunit prokaryotic ribosomes containing 1600 nucleotides and 21 proteins. 16S rRNA is involved in initiation of polypeptide synthesis.

A colorless, odorless gas that can be formed by the body and is necessary for the respiration cycle of plants and animals.

Creation and development of bodies within solar systems, includes study of early planetary geology.

A group (or phylum) of unicellular EUKARYOTA (or algae) possessing CHLOROPLASTS and FLAGELLA.

Marine ridges composed of living CORALS, coral skeletons, calcareous algae, and other organisms, mixed with minerals and organic matter. They are found most commonly in tropical waters and support other animal and plant life.

The pattern of any process, or the interrelationship of phenomena, which affects growth or change within a population.

A nonmetallic element with atomic symbol C, atomic number 6, and atomic weight [12.0096; 12.0116]. It may occur as several different allotropes including DIAMOND; CHARCOAL; and GRAPHITE; and as SOOT from incompletely burned fuel.

One of the Indian Ocean Islands, east of Madagascar. Its capital is Saint-Denis. It was discovered in 1507 by the Portuguese and claimed by France in 1638. It was first colonized in 1662 as Isle de Bourbon but renamed Reunion in 1793. In 1946 it was made an overseas department of France. The name commemorates the reunion of the revolutionaries from Marseilles with the National Guard in Paris in 1792. (From Webster's New Geographical Dictionary, 1988, p1011; Room, Brewer's Dictionary of Names, 1992, p454; French Embassy)

The sequence of transfers of matter and energy from organism to organism in the form of FOOD. Food chains intertwine locally into a food web because most organisms consume more than one type of animal or plant. PLANTS, which convert SOLAR ENERGY to food by PHOTOSYNTHESIS, are the primary food source. In a predator chain, a plant-eating animal is eaten by a larger animal. In a parasite chain, a smaller organism consumes part of a larger host and may itself be parasitized by smaller organisms. In a saprophytic chain, microorganisms live on dead organic matter.

Total mass of all the organisms of a given type and/or in a given area. (From Concise Dictionary of Biology, 1990) It includes the yield of vegetative mass produced from any given crop.

A species of SEA URCHINS in the family Strongylocentrotidae found on the Pacific coastline from Alaska to Mexico. This species serves as a major research model for molecular developmental biology and other fields.

The sole family in the order Sphenisciformes, comprised of 17 species of penguins in six genera. They are flightless seabirds of the Southern Hemisphere, highly adapted for marine life.

Descriptions of specific amino acid, carbohydrate, or nucleotide sequences which have appeared in the published literature and/or are deposited in and maintained by databanks such as GENBANK, European Molecular Biology Laboratory (EMBL), National Biomedical Research Foundation (NBRF), or other sequence repositories.

The effect of GLOBAL WARMING and the resulting increase in world temperatures. The predicted health effects of such long-term climatic change include increased incidence of respiratory, water-borne, and vector-borne diseases.

Degree of saltiness, which is largely the OSMOLAR CONCENTRATION of SODIUM CHLORIDE plus any other SALTS present. It is an ecological factor of considerable importance, influencing the types of organisms that live in an ENVIRONMENT.

A multistage process that includes cloning, physical mapping, subcloning, determination of the DNA SEQUENCE, and information analysis.

A British colony in the western North Atlantic Ocean about 640 miles east southeast of Cape Hatteras, North Carolina. It comprises a group of about 300 islands of which only about 20 are inhabited. It is called also the Bermuda Islands or the Bermudas. It was named for the Spanish explorer Juan Bermudez who visited the islands in 1515. (From Webster's New Geographical Dictionary, 1988, p140 & Room, Brewer's Dictionary of Names, 1992, p61)

One of the three domains of life (the others being Eukarya and ARCHAEA), also called Eubacteria. They are unicellular prokaryotic microorganisms which generally possess rigid cell walls, multiply by cell division, and exhibit three principal forms: round or coccal, rodlike or bacillary, and spiral or spirochetal. Bacteria can be classified by their response to OXYGEN: aerobic, anaerobic, or facultatively anaerobic; by the mode by which they obtain their energy: chemotrophy (via chemical reaction) or PHOTOTROPHY (via light reaction); for chemotrophs by their source of chemical energy: CHEMOLITHOTROPHY (from inorganic compounds) or chemoorganotrophy (from organic compounds); and by their source for CARBON; NITROGEN; etc.; HETEROTROPHY (from organic sources) or AUTOTROPHY (from CARBON DIOXIDE). They can also be classified by whether or not they stain (based on the structure of their CELL WALLS) with CRYSTAL VIOLET dye: gram-negative or gram-positive.

The science of the earth and other celestial bodies and their history as recorded in the rocks. It includes the study of geologic processes of an area such as rock formations, weathering and erosion, and sedimentation. (From McGraw-Hill Dictionary of Scientific and Technical Terms, 6th ed)

A mature haploid female germ cell extruded from the OVARY at OVULATION.

The protection, preservation, restoration, and rational use of all resources in the total environment.

A species of ALPHAVIRUS causing an acute dengue-like fever.

The property of objects that determines the direction of heat flow when they are placed in direct thermal contact. The temperature is the energy of microscopic motions (vibrational and translational) of the particles of atoms.

The enrichment of a terrestrial or aquatic ECOSYSTEM by the addition of nutrients, especially nitrogen and phosphorus, that results in a superabundant growth of plants, ALGAE, or other primary producers. It can be a natural process or result from human activity such as agriculture runoff or sewage pollution. In aquatic ecosystems, an increase in the algae population is termed an algal bloom.

Divisions of the year according to some regularly recurrent phenomena usually astronomical or climatic. (From McGraw-Hill Dictionary of Scientific and Technical Terms, 6th ed)

Tracts of land completely surrounded by water.

A group of the proteobacteria comprised of facultatively anaerobic and fermentative gram-negative bacteria.

Fish-eating carnivores of the family MUSTELIDAE, found on both hemispheres.

A class in the phylum PROTEOBACTERIA comprised mostly of two major phenotypes: purple non-sulfur bacteria and aerobic bacteriochlorophyll-containing bacteria.

Common name for various species of large, vigorous ocean fishes in the family Scombridae.

DNA sequences encoding RIBOSOMAL RNA and the segments of DNA separating the individual ribosomal RNA genes, referred to as RIBOSOMAL SPACER DNA.

Communications using an active or passive satellite to extend the range of radio, television, or other electronic transmission by returning signals to earth from an orbiting satellite.

Instinctual behavior pattern in which food is obtained by killing and consuming other species.

Virus diseases caused by members of the ALPHAVIRUS genus of the family TOGAVIRIDAE.

A kingdom in the domain ARCHAEA comprised of thermoacidophilic, sulfur-dependent organisms. The two orders are SULFOLOBALES and THERMOPROTEALES.

The branch of science concerned with the interrelationship of organisms and their ENVIRONMENT, especially as manifested by natural cycles and rhythms, community development and structure, interactions between different kinds of organisms, geographic distributions, and population alterations. (Webster's, 3d ed)

Large vessels propelled by power or sail used for transportation on rivers, seas, oceans, or other navigable waters. Boats are smaller vessels propelled by oars, paddles, sail, or power; they may or may not have a deck.

The restriction of a characteristic behavior, anatomical structure or physical system, such as immune response; metabolic response, or gene or gene variant to the members of one species. It refers to that property which differentiates one species from another but it is also used for phylogenetic levels higher or lower than the species.

One of the three domains of life (the others being BACTERIA and ARCHAEA), also called Eukarya. These are organisms whose cells are enclosed in membranes and possess a nucleus. They comprise almost all multicellular and many unicellular organisms, and are traditionally divided into groups (sometimes called kingdoms) including ANIMALS; PLANTS; FUNGI; and various algae and other taxa that were previously part of the old kingdom Protista.

One of the three domains of life (the others being BACTERIA and Eukarya), formerly called Archaebacteria under the taxon Bacteria, but now considered separate and distinct. They are characterized by: (1) the presence of characteristic tRNAs and ribosomal RNAs; (2) the absence of peptidoglycan cell walls; (3) the presence of ether-linked lipids built from branched-chain subunits; and (4) their occurrence in unusual habitats. While archaea resemble bacteria in morphology and genomic organization, they resemble eukarya in their method of genomic replication. The domain contains at least four kingdoms: CRENARCHAEOTA; EURYARCHAEOTA; NANOARCHAEOTA; and KORARCHAEOTA.

A field of study concerned with the principles and processes governing the geographic distributions of genealogical lineages, especially those within and among closely related species. (Avise, J.C., Phylogeography: The History and Formation of Species. Harvard University Press, 2000)

The species Megaptera novaeangliae, in the family Balaenopteridae, characterized by its huge flippers and the arching of their back when diving. They are also known for their breaching and singing.

The hard rigid covering of animals including MOLLUSCS; TURTLES; INSECTS; and crustaceans.

Techniques used to determine the age of materials, based on the content and half-lives of the RADIOACTIVE ISOTOPES they contain.

Animals that have no spinal column.

A huge subclass of mostly marine CRUSTACEA, containing over 14,000 species. The 10 orders comprise both planktonic and benthic organisms, and include both free-living and parasitic forms. Planktonic copepods form the principle link between PHYTOPLANKTON and the higher trophic levels of the marine food chains.

The family Phocidae, suborder PINNIPEDIA, order CARNIVORA, comprising the true seals. They lack external ears and are unable to use their hind flippers to walk. It includes over 18 species including the harp seal, probably the best known seal species in the world.

Common name for FISHES belonging to the order Perciformes and occurring in three different families.

Any of several processes for the permanent or long-term artificial or natural capture or removal and storage of carbon dioxide and other forms of carbon, through biological, chemical or physical processes, in a manner that prevents it from being released into the atmosphere.

A phylum of radially symmetrical invertebrates characterized by possession of stinging cells called nematocysts. It includes the classes ANTHOZOA; CUBOZOA; HYDROZOA, and SCYPHOZOA. Members carry CNIDARIAN VENOMS.

Remains, impressions, or traces of animals or plants of past geological times which have been preserved in the earth's crust.

A class of marine annelids including sandworms, tube worms, clamworms, and fire worms. It includes also the genus Myxicola infundibulum.

The solid substance formed by the FREEZING of water.

A class in the phylum MOLLUSCA comprised of mussels; clams; OYSTERS; COCKLES; and SCALLOPS. They are characterized by a bilaterally symmetrical hinged shell and a muscular foot used for burrowing and anchoring.

Chemical compounds which yield hydrogen ions or protons when dissolved in water, whose hydrogen can be replaced by metals or basic radicals, or which react with bases to form salts and water (neutralization). An extension of the term includes substances dissolved in media other than water. (Grant & Hackh's Chemical Dictionary, 5th ed)

The ash, dust, gases, and lava released by volcanic explosion. The gases are volatile matter composed principally of about 90% water vapor, and carbon dioxide, sulfur dioxide, hydrogen, carbon monoxide, and nitrogen. The ash or dust is pyroclastic ejecta and lava is molten extrusive material consisting mainly of magnesium silicate. (From McGraw-Hill Dictionary of Scientific and Technical Terms, 4th ed)

Process by which organic tissue becomes hardened by the physiologic deposit of calcium salts.

An order of amoeboid EUKARYOTES characterized by reticulating pseudopods and a complex life cycle with an alternation of generations. Most are less than 1mm in size and found in marine or brackish water.

Wormlike or grublike stage, following the egg in the life cycle of insects, worms, and other metamorphosing animals.

The external elements and conditions which surround, influence, and affect the life and development of an organism or population.

A group of Indian Ocean Islands, east of Tanzania. Their capital is Victoria. They were first claimed by the French in 1744 but taken by the English in 1794 and made a dependency of MAURITIUS in 1810. They became a crown colony in 1903 and a republic within the Commonwealth in 1976. They were named for the French finance minister, Jean Moreau de Sechelles, but respelled by the English in 1794. (From Webster's New Geographical Dictionary, 1988, p1102 & Room, Brewer's Dictionary of Names, 1992, p496)

Large natural streams of FRESH WATER formed by converging tributaries and which empty into a body of water (lake or ocean).

A form-genus of spherical to rod-shaped CYANOBACTERIA in the order Chroococcales. They contain THYLAKOIDS and are found in a wide range of habitats.

Genotypic differences observed among individuals in a population.

Water containing no significant amounts of salts, such as water from RIVERS and LAKES.

Venoms from jellyfish; CORALS; SEA ANEMONES; etc. They contain hemo-, cardio-, dermo- , and neuro-toxic substances and probably ENZYMES. They include palytoxin, sarcophine, and anthopleurine.

The species Physeter catodon (also called Physeter macrocephalus), in the family Physeteridae. The common name is derived from the milky wax substance in its head (spermaceti). The species also produces an intestinal secretion AMBERGRIS, which was previously used in perfumes. The sperm whale is the largest toothed MAMMAL in the world.

A vertical distance measured from a known level on the surface of a planet or other celestial body.

The spectrum of different living organisms inhabiting a particular region, habitat, or biotope.

The process of cumulative change over successive generations through which organisms acquire their distinguishing morphological and physiological characteristics.

Sulfur compounds in which the sulfur atom is attached to three organic radicals and an electronegative element or radical.

Deoxyribonucleic acid that makes up the genetic material of bacteria.

The monitoring of the level of toxins, chemical pollutants, microbial contaminants, or other harmful substances in the environment (soil, air, and water), workplace, or in the bodies of people and animals present in that environment.

A group of elongate elasmobranchs. Sharks are mostly marine fish, with certain species large and voracious.

The practice of medicine concerned with conditions affecting the health of individuals associated with the marine environment.

A group comprised of several species of eared seals found in two genera, in the family Otariidae. In comparison to SEA LIONS, they have an especially dense wooly undercoat.

Genes, found in both prokaryotes and eukaryotes, which are transcribed to produce the RNA which is incorporated into RIBOSOMES. Prokaryotic rRNA genes are usually found in OPERONS dispersed throughout the GENOME, whereas eukaryotic rRNA genes are clustered, multicistronic transcriptional units.

The normality of a solution with respect to HYDROGEN ions; H+. It is related to acidity measurements in most cases by pH = log 1/2[1/(H+)], where (H+) is the hydrogen ion concentration in gram equivalents per liter of solution. (McGraw-Hill Dictionary of Scientific and Technical Terms, 6th ed)

Flagellate EUKARYOTES, found mainly in the oceans. They are characterized by the presence of transverse and longitudinal flagella which propel the organisms in a rotating manner through the water. Dinoflagellida were formerly members of the class Phytomastigophorea under the old five kingdom paradigm.

A large subphylum of mostly marine ARTHROPODS containing over 42,000 species. They include familiar arthropods such as lobsters (NEPHROPIDAE), crabs (BRACHYURA), shrimp (PENAEIDAE), and barnacles (THORACICA).

The genomic analysis of assemblages of organisms.

A genus of SEA URCHINS in the family Strongylocentrotidae. They possess more than three pore pairs per ambulacral plate. The species STRONGYLOCENTROTUS PURPURATUS is commonly used for research.

The suborder of aquatic CARNIVORA comprising the WALRUSES; FUR SEALS; SEA LIONS; and EARLESS SEALS. They have fusiform bodies with very short tails and are found on all sea coasts. The offspring are born on land.

The period of history before 500 of the common era.

A phylum of oxygenic photosynthetic bacteria comprised of unicellular to multicellular bacteria possessing CHLOROPHYLL a and carrying out oxygenic PHOTOSYNTHESIS. Cyanobacteria are the only known organisms capable of fixing both CARBON DIOXIDE (in the presence of light) and NITROGEN. Cell morphology can include nitrogen-fixing heterocysts and/or resting cells called akinetes. Formerly called blue-green algae, cyanobacteria were traditionally treated as ALGAE.

Water waves caused by the gravitational interactions between the EARTH; MOON; and SUN.

Large marine mammals of the order CETACEA. In the past, they were commercially valued for whale oil, for their flesh as human food and in ANIMAL FEED and FERTILIZERS, and for baleen. Today, there is a moratorium on most commercial whaling, as all species are either listed as endangered or threatened.

Fish of the genera ONCORHYNCHUS and Salmo in the family SALMONIDAE. They are anadromous game fish, frequenting the coastal waters of both the North Atlantic and Pacific. They are known for their gameness as a sport fish and for the quality of their flesh as a table fish. (Webster, 3d ed).

An activity in which the organism plunges into water. It includes scuba and bell diving. Diving as natural behavior of animals goes here, as well as diving in decompression experiments with humans or animals.

Echinoderms having bodies of usually five radially disposed arms coalescing at the center.

Thorium. A radioactive element of the actinide series of metals. It has an atomic symbol Th, atomic number 90, and atomic weight 232.04. It is used as fuel in nuclear reactors to produce fissionable uranium isotopes. Because of its radioopacity, various thorium compounds are used to facilitate visualization in roentgenography.

A climate which is typical of equatorial and tropical regions, i.e., one with continually high temperatures with considerable precipitation, at least during part of the year. (McGraw-Hill Dictionary of Scientific and Technical Terms, 4th ed)

A process facilitated by specialized bacteria involving the oxidation of ammonium to nitrite and nitrate.

The phylum of sponges which are sessile, suspension-feeding, multicellular animals that utilize flagellated cells called choanocytes to circulate water. Most are hermaphroditic. They are probably an early evolutionary side branch that gave rise to no other group of animals. Except for about 150 freshwater species, sponges are marine animals. They are a source of ALKALOIDS; STEROLS; and other complex molecules useful in medicine and biological research.

Number of individuals in a population relative to space.

Porphyrin derivatives containing magnesium that act to convert light energy in photosynthetic organisms.

The largest order of CRUSTACEA, comprising over 10,000 species. They are characterized by three pairs of thoracic appendages modified as maxillipeds, and five pairs of thoracic legs. The order includes the familiar shrimps, crayfish (ASTACOIDEA), true crabs (BRACHYURA), and lobsters (NEPHROPIDAE and PALINURIDAE), among others.

The dimension of the physical universe which, at a given place, orders the sequence of events. (McGraw-Hill Dictionary of Scientific and Technical Terms, 6th ed)

The relative amounts of the PURINES and PYRIMIDINES in a nucleic acid.

The synthesis by organisms of organic chemical compounds, especially carbohydrates, from carbon dioxide using energy obtained from light rather than from the oxidation of chemical compounds. Photosynthesis comprises two separate processes: the light reactions and the dark reactions. In higher plants; GREEN ALGAE; and CYANOBACTERIA; NADPH and ATP formed by the light reactions drive the dark reactions which result in the fixation of carbon dioxide. (from Oxford Dictionary of Biochemistry and Molecular Biology, 2001)

A climate characterized by COLD TEMPERATURE for a majority of the time during the year.

Theoretical representations that simulate the behavior or activity of systems, processes, or phenomena. They include the use of mathematical equations, computers, and other electronic equipment.

One of the Indian Ocean Islands off the southeast coast of Africa. Its capital is Antananarivo. It was formerly called the Malagasy Republic. Discovered by the Portuguese in 1500, its history has been tied predominantly to the French, becoming a French protectorate in 1882, a French colony in 1896, and a territory within the French union in 1946. The Malagasy Republic was established in the French Community in 1958 but it achieved independence in 1960. Its name was changed to Madagascar in 1975. (From Webster's New Geographical Dictionary, 1988, p714)

A genus of primitive fish in the family Petromyzontidae. The sole species is Petromyzon marinus, known as the sea lamprey. The adult form feeds parasitically on other fish species.

Multicellular marine macroalgae including some members of red (RHODOPHYTA), green (CHLOROPHYTA), and brown (PHAEOPHYTA) algae. They are widely distributed in the ocean, occurring from the tide level to considerable depths, free-floating (planktonic) or anchored to the substratum (benthic). They lack a specialized vascular system but take up fluids, nutrients, and gases directly from the water. They contain CHLOROPHYLL and are photosynthetic, but some also contain other light-absorbing pigments. Many are of economic importance as FOOD, fertilizer, AGAR, potash, or source of IODINE.

Cultivation of natural faunal resources of water. (McGraw-Hill Dictionary of Scientific and Technical Terms, 4th ed)

The circulation of nitrogen in nature, consisting of a cycle of biochemical reactions in which atmospheric nitrogen is compounded, dissolved in rain, and deposited in the soil, where it is assimilated and metabolized by bacteria and plants, eventually returning to the atmosphere by bacterial decomposition of organic matter.

Activities performed by humans.

Constituent of the 40S subunit of eukaryotic ribosomes. 18S rRNA is involved in the initiation of polypeptide synthesis in eukaryotes.

Stable oxygen atoms that have the same atomic number as the element oxygen, but differ in atomic weight. O-17 and 18 are stable oxygen isotopes.

Chemical groups containing the covalent sulfur bonds -S-. The sulfur atom can be bound to inorganic or organic moieties.

Chemical compounds which pollute the water of rivers, streams, lakes, the sea, reservoirs, or other bodies of water.

A hydrated form of silicon dioxide. It is commonly used in the manufacture of TOOTHPASTES and as a stationary phase for CHROMATOGRAPHY.

Toxic or poisonous substances elaborated by marine flora or fauna. They include also specific, characterized poisons or toxins for which there is no more specific heading, like those from poisonous FISHES.

Characteristic events occurring in the ATMOSPHERE during the interactions and transformation of various atmospheric components and conditions.

The study of early forms of life through fossil remains.

A large supergroup of mostly amoeboid EUKARYOTES whose three main subgroups are CERCOZOA; FORAMINIFERA; and HAPLOSPORIDA. Nearly all of the species possess MITOCHONDRIA and historically many were considered ANIMALS.

The science of studying the characteristics of the atmosphere such as its temperature, density, winds, clouds, precipitation, and other atmospheric phenomena and aiming to account for the weather in terms of external influences and the basic laws of physics. (From McGraw-Hill Dictionary of Scientific and Technical Terms, 6th ed)

The developmental entity of a fertilized egg (ZYGOTE) in animal species other than MAMMALS. For chickens, use CHICK EMBRYO.

Diseases of freshwater, marine, hatchery or aquarium fish. This term includes diseases of both teleosts (true fish) and elasmobranchs (sharks, rays and skates).

An order of fish including the families Gadidae (cods), Macrouridae (grenadiers), and hakes. The large Gadidae family includes cod, haddock, whiting, and pollock.

Double-stranded DNA of MITOCHONDRIA. In eukaryotes, the mitochondrial GENOME is circular and codes for ribosomal RNAs, transfer RNAs, and about 10 proteins.

The ceasing of existence of a species or taxonomic groups of organisms.

A genus of SEA URCHINS in the family Toxopneustidae possessing trigeminate ambulacral plating.

Adaptation to a new environment or to a change in the old.

Ongoing collection, analysis, and interpretation of ecological data that is used to assess changes in the components, processes, and overall condition and functioning of an ECOSYSTEM.

A family in the order Rhodobacterales, class ALPHAPROTEOBACTERIA.

A genus of obligately aerobic marine phototrophic and chemoorganotrophic bacteria, in the family RHODOBACTERACEAE.

The science that deals with the ocean and its phenomena. (Webster, 3d ed)

Mammals of the families Delphinidae (ocean dolphins), Iniidae, Lipotidae, Pontoporiidae, and Platanistidae (all river dolphins). Among the most well-known species are the BOTTLE-NOSED DOLPHIN and the KILLER WHALE (a dolphin). The common name dolphin is applied to small cetaceans having a beaklike snout and a slender, streamlined body, whereas PORPOISES are small cetaceans with a blunt snout and rather stocky body. (From Walker's Mammals of the World, 5th ed, pp978-9)

An element with the atomic symbol N, atomic number 7, and atomic weight [14.00643; 14.00728]. Nitrogen exists as a diatomic gas and makes up about 78% of the earth's atmosphere by volume. It is a constituent of proteins and nucleic acids and found in all living cells.

The relationship between two different species of organisms that are interdependent; each gains benefits from the other or a relationship between different species where both of the organisms in question benefit from the presence of the other.

Large, robust forms of brown algae (PHAEOPHYCEAE) in the order Laminariales. They are a major component of the lower intertidal and sublittoral zones on rocky coasts in temperate and polar waters. Kelp, a kind of SEAWEED, usually refers to species in the genera LAMINARIA or MACROCYSTIS, but the term may also be used for species in FUCUS or Nereocystis.

Warm-blooded VERTEBRATES possessing FEATHERS and belonging to the class Aves.

The process in certain BACTERIA; FUNGI; and CYANOBACTERIA converting free atmospheric NITROGEN to biologically usable forms of nitrogen, such as AMMONIA; NITRATES; and amino compounds.

Instinctual patterns of activity related to a specific area including ability of certain animals to return to a given place when displaced from it, often over great distances using navigational clues such as those used in migration (ANIMAL MIGRATION).

Contamination of bodies of water (such as LAKES; RIVERS; SEAS; and GROUNDWATER.)

An animal or plant species in danger of extinction. Causes can include human activity, changing climate, or change in predator/prey ratios.

A process by which animals in various forms and stages of development are physically distributed through time and space.

The sequence of PURINES and PYRIMIDINES in nucleic acids and polynucleotides. It is also called nucleotide sequence.

A partially enclosed body of water, and its surrounding coastal habitats, where saltwater from the ocean mixes with fresh water from rivers or streams. The resulting mixture of seawater and fresh water is called brackish water and its salinity can range from 0.5 to 35 ppt. (accessed http://oceanservice.noaa.gov/education/kits/estuaries/estuaries01_whatis.html)

Events and activities of the Earth and its structures.

A subclass of cartilaginous fish comprising the SHARKS; rays; skates (SKATES (FISH);), and sawfish. Elasmobranchs are typically predaceous, relying more on smell (the olfactory capsules are relatively large) than sight (the eyes are relatively small) for obtaining their food.

The fusion of a spermatozoon (SPERMATOZOA) with an OVUM thus resulting in the formation of a ZYGOTE.

A common name (but used formally) for a group of organisms that are mostly kinds of algae including BACILLARIOPHYTA; OOMYCETES; PHAEOPHYCEAE; and CHRYSOPHYCEAE. They all contain CHLOROPLASTS that are thought to have been derived from the endosymbiosis of ancient RED ALGAE.

Celestial bodies orbiting around the sun or other stars.

The species Orcinus orca, in the family Delphinidae, characterized by its black and white coloration, and huge triangular dorsal fin. It is the largest member of the DOLPHINS and derives its name from the fact that it is a fearsome predator.

The geographical area of Africa comprising BURUNDI; DJIBOUTI; ETHIOPIA; KENYA; RWANDA; SOMALIA; SUDAN; TANZANIA; and UGANDA.

The process of cumulative change at the level of DNA; RNA; and PROTEINS, over successive generations.

An order of BIRDS including over 300 species that primarily inhabit coastal waters, beaches, and marshes. They are comprised of shorebirds, gulls, and terns.

A plant genus of the family RANUNCULACEAE that contains triterpene saponins. The root of Anemone raddeana is the source of a Chinese folk medicine, zhu jie xian fu. The common name of liverwort is also used with other plants. This genus is unrelated to SEA ANEMONES.

Infestations by PARASITES which live on, or burrow into, the surface of their host's EPIDERMIS. Most ectoparasites are ARTHROPODS.

El Nino-Southern Oscillation or ENSO is a cycle of extreme alternating warm El Niño and cold La Nina events which is the dominant year-to-year climate pattern on Earth. Both terms refer to large-scale changes in sea-surface temperature across the eastern tropical Pacific. ENSO is associated with a heightened risk of certain vector-borne diseases. (From http://www.elnino.noaa.gov/lanina_new_faq.html, accessed 5/12/2020)