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  • Glossary
| Last Updated:01/02/2018



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an internode of the floral axis between the corolla and stamens bearing the stamens and the pistil


Natural underground reservoir of water.


arranged in a zig-zag manner, neither opposite nor whorled

Antarctic Divergence

The region along the southern edge of the Antarctic Circumpolar Current where surface waters are diverging

Absolute zero

The coldest possible temperature


Taking in of a substance by chemical or molecular mans; change of sound or light energy into some other form, usually heat, in passing through a medium or striking a surface.


Pertaining to the great depths of the ocean below approximately 4000 m

Abyssal hill

Low, rounded submarine hill less than 1000 m high.


Natural or artificial deposition of sediment along a beach, resulting in the buildup of new land


situated in the axil, usually in the axil of stem and leaf


with a short, but not rigid point


increase in size with age (usually of calyx)

Authigenic sediment

Sediment formed directly by precipitation from seawater. Also called hydrogenous sediment




an appendage arising from the hilum and covering the seed


without petals or corolla


Arising from human activity.

Aquatic organisms

Organisms that live in or on the water.

Abiotic factors (abiotic)

Non-living characteristics of a habitat or ecosystem that affect organisms' life processes.

Adaptation (adapt)

A genetically-based body feature or behavior that allows an organism to be better suited to its environment.

anoxic waters

areas of sea water or fresh water that are depleted of dissolved oxygen.


Without air, no oxygen.

Antarctic Ocean

An ocean in the southern Hemisphere bounded to the north by the Antarctic Convergence and to the south by Antarctica


Moving in a clockwise direction


Portion of standing wave with maximum vertical motion


The point in the orbit of a satellite where it is farthest from the sun


Without light; that area of the oceans without light

Aphotic zone

That part of the ocean in which light is insufficient to carry on photosynthesis


That point during the orbit of the moon around the earth when the moon is farthest from the earth

Aquaculture (mariculture)

Cultivation of aquatic organisms under controlled conditions


Living or existing within or on water


Artemisinin Combination Therapy

Assortative mating

The mating of a given genotype with another genotype at a frequency disproportionate to that expected from a series of random encounters


The class of the phylum Echinodermata to which se stars belong


Upper, deformable portion of the Earth�s mantle, the layer below the lithosphere; probably partially molten; may be site of convection cells

Atmospheric circulation cell

Large circuit of air driven by uneven solar heating and the Coriolis effect. Three circulation cells form in each hemisphere. See also Hadley cell; Ferrel cell; Polar cell

Atmospheric pressure

Pressure, at any point on Earth, exerted by the atmosphere as a consequence of gravitational force exerted upon the column of air lying directly above the point


Ring-shaped coral reef that encloses a lagoon in which there is o exposed preexisting land and which is surrounded by the open sea

Antarctic Convergence

A region where the surface waters converge at the northern edge of the Antarctic Circumpolar current, located at about 50�S latitude in all oceans


Automatic Weather Stations


Assam Science, Technology & Environmental Council

Absolute scale

A temperature scale on which absolute zero is 0 k, water freezes at 273 K, and water boils at 373 K. (The degree has the same size at a Celsius degree)

Acoustical tomography

A technique for studying ocean structure that depends on pulses of low-frequency sound to sense differences in water temperature, salinity, and movement beneath the surface


The fundamental constituent of matter, made up of a very small, dense, positively charged nucleus, surrounded by a cloud of negatively charged electrons.

Atomic magnets

A term referring to the fact that many atoms have small amounts of magnetism, due to the motions of the electrical charges within them

Atomic mass number

The total number of protons and nucleons in the nucleus of an atom


Decrease in the energy of a wave or beam of particles occurring as the distance from the source increases; caused by absorption, scattering and divergence from a point source


Sediment that is derived from sea water and precipitates directly on to the ocean floor, as opposed to falling a column of water first


Adverse Effects After Immunization


Agharkar Research Institute


narrowed , tapered (usually at base)


Adverse Effect After Immunization


a bristle - like terminal appendage

Abyssal plain

Flat ocean-basin floor extending seaward from the base of the continental slope and continental rise.

Abyssal zone

The ocean between about 4,000 and 5,000 meters (13,000 and 16,500 feet) deep


Oceanic zone from 4000 m to the deepest depths.


A substance that releases a hydrogen ion in solution


An organism that make its own food by photosynthesis or chemosynthesis


Pertaining to organisms able to manufacture their own food from inorganic substances. See also chemosynthesis and photosynthesis


In reproduction, without involving sex

Asexual reproduction

Reproduction of the individual without the production of gametes and zygotes


a hard, dry, indehiscent, one-seeded fruit with a single cavity


at the terminal point of any structure

Active transport

The movement of molecules from a region of low concentration to a region of high concentration through a semi permeable membrane at the expense of energy


An organism that makes its own food from light energy or chemical energy without eating. Most green plants, many protists and most bacteria are autotrophs. Autotrophs are the base of the food chain and can also be called producers.


Marine and freshwater organisms (including most seaweeds) that are single celled, colonial or multi-celled, with chlorophyll but no true roots, stems, or leaves and with no flowers or seeds.

Algal ridge

Coral-free ridge of encrusting coralline algae lying immediately behind the buttress zone


Complex organic substance found in or obtained from brown algae

Alien animal

Animal that is not indigenous to the area


A measure of the concentration of hydroxyl ions in a solution


Very intense or sharp


An inheritable structural or behavioral modification. A favorable adaptation give a species an advantage in survival and reproduction. An un-favorable adaptation lessens a species ability to survive and reproduce

Adenosine triphosphate

The energy storage molecule of most living systems


Attachment of water molecules to other substances by hydrogen bonds. Wetting

Allopatric speciation

The differentiation of geographically isolated populations into distinct species Allozyme A variant of an enzyme type. These may be variants of a specific enzyme (e.g. cytochrome c) that are the products of a single genetic locus

Adiabatic processes

Processes in which changes in temperature are caused by expansion or compression, and not the addition or removal of heat


Attraction of ions to a solid surface


Horizontal or vertical transport of seawater, as by a current


Tissue of thin-walled cells and spaces found in stems and roots of certain marsh plants serving to transfer oxygen


Condition in which oxygen is present


Substance produced by red algae; the gelatin like product of these algae

Age structure

The relative abundance of different age classes in a population Aggregated spatial distribution


The class of jawless fishes; hagfishes and lampreys


Non-reef-building (referring to scleractinian corals)

Ahermatypic coral

A nonreef-producing coral without the symbiotic zooxanthellae in the tissues

Air mass

A large mass of air with nearly uniform temperature, humidity and density throughout


One of several variants that can occupy a locus on a chromosome


Of foreign origin; transported into the area from outside


Non-living chemical and physical factors in the environment.

Amphidromic point

Point from which cotidal lines radiate or a chart; the nodal, or low amplitude, point for a rotary tide.


Insect like crustaceans with bodies that are flattened from side to side


The term disease causative agent usually refers to a living, biological organism that causes a disease.

Arctic and Antarctic circles

Latitudes 66 �� N and 66 1/2 �S respectively, marking the boundaries of light and darkness during the summer and winter solstices.

Arctic Convergence

Convergence zone between Arctic Water and Subarctic Surface Water

Arctic Ocean

An ice-covered ocean north of the continents of North America and Eurasia

Armored beach

A beach from which the waves have removed the finer sediments, leaving a rocky surface

Arrow worms

Members of the phylum Chaetognatha; a group of planktonic carnivores


The phylum of animals that includes shrimp, lobsters, krill, barnacles, and insects. The phylum Arthropoda is the world�s must successful


Members of the phylum Arthropoda, which includes all animals with jointed legs and external skeletons (e.g., crustaceans and insects)

Alternation of generations

A reproductive cycle in which a plant alternates between sexual and asexual stages

Alternative stable states

Two configurations of species abundances in a habitat, each of which tends to be stable under certain conditions. Usually it takes a large disturbance to cause a shift from one stable state to another

A mensal

Negatively affecting one or several species

Alluvial plain

Flat deposit of terrestrial sediment eroded by water from higher elevations


Refers to young birds that are hatched in an immature state requiring extended parental care

American estuary

An estuary dominated by extensive stands of emergent vegetation surrounding less extensive mud flats

Amino acids

The basic structural units of proteins


A material whose molecules are made up of one nitrogen atom and three hydrogens, NH3


For a wave, the vertical distance from sea level to crest or from undisturbed sea level to trough, or one-half the wave height.

Anadromous fish

Fish that spends most of its life feeding in the open ocean but that migrates to spawn in fresh water


Living or functioning in the absence of oxygen

Anaerobic bacteria

Bacteria that can decompose organic matter in the absence of free oxygen, using other oxidizing agents instead


Common name for Engraulis ringens, the Peruvian anchovy


Type of volcanic rock that is intermediate in composition between basalt and granite; associated with subduction zones


A common coelenterate animal in tide pools that looks like a flower and has tentacles that is uses to capture food particles and small prey


A flowering vascular plant that reproduces by means of a seed-bearing fruit. Examples are sea grasses and mangroves


A multicellular organism unable to synthesize its own food and often capable of movement


Acclimatization refers to phenotypic changes by an organism to stresses in the natural environment that result in the readjustment of the organism's tolerance.


The phylum of animals to which segmented worms belong


Negatively changed ion


Deficient in oxygen

Antarctic Boom Water (ABW)

The densest of the major deep water masses. It is formed beneath ice neat Antarctica and flows northward along the bottom of the Atlantic Ocean


Asian Development Bank


Assam Science, Technology & Environmental Council


Acquired Immune Deficiency Syndrome


The last of the three parts of an insect’s body. There you can find their heart, digestive system, and reproductive organs.

Anther – lobe

pollen containing sac of the stamen


the fusion of unlike parts


tapering to the apex with the sides straight or nearly so; usually less tapering than acuminate


tapering to a pointed apex, sides more or less pinched in before reaching the tip


Formed or occurring in the place where it is found

Assimilation efficiency

The fraction of ingested food that is absorbed and used in metabolism


The class of birds

Autotrophic alga

Algae requiring a few organically derived substances, swuch as vitamins, along with dissolved inorganic nutrients, for photosynthesis

Accessory pigment

One of a class of pigments (such as fucoxanthin, phycobilin, and xanthophyll) present in various photosynthetic plants and which assist in the absorption of light and the transfer of its energy to chlorophyll. Also called masking pigment

Abyssal clays

Fine-grained inorganic sediments that cover large portions of the deep ocean floor

Abyssal gigantism

Phenomenon observed among several crustacean group on which general size in creases with increasing depth

Abyssopelagic zone

The 4,000-6000 m depth zone, sea ward of the shelfs-slope break

Acid rain

Rain containing acids and acid forming compounds such as sulfur dioxide and oxides of nitrogen


A measure of the concentration of hydrogen ions in a solution

Acoustic profiling

The use of seismic energy to measure sediment thickness and layering on the sea floor

Arctic Marine Environment

This is a biome made up of the Arctic Ocean including areas with permanent ice cover.

Alternate stable states

The occurrence in a single habitat of several different persistent communities in which the structure of each is the result of historical events


Relating to high mountains.


A person who believes in a cause or issue and takes action to promote it


The kingdom to which multicellular heterotrphos belong


Having no recurring order in the arrangement of atomic groups. Not crystalline Amphidromic motion The large scale circular motion of water, resulting from Coriolis deflection


An animal that typically lives partially in an aquatic habitat (breathing by gills) as young and primarily in a terrestrial habitat (breathing by lungs and through moist skin) as an adult, e.g. frogs.


The process of preparing the land to grow food, producing crops, and raising animals.

Anchor ice

Ice that forms around any convenient nucleus in the area below the permanent pack ice in Antarctica; it tends to carry organisms out of the area to be incorporated in the sea ice above

Antarctic Circumpolar Current

A major ocean current driven eastward around the entire Earth at about 50 to 60�S latitude by the prevailing westerlies

Archimedes principle

Any object that is immersed in a fluid receives an upward buoyant force that is equal to the weight of the fluid displaced

Antarctic Circumpolar Water (ACW)

The water of the Antarctic Circumpolar Current, found at about 50 to 60�S latitude. It extends from the surface to the ocean bottom, except where the Antarctic Bottom Water flows beneath it in the Atlantic

Artificial system of classification

A method of classifying an object based on attributes other than its reason for existence, its ancestry, or its origin. Compare natural system of classification

Alluvial fans

The large fan-shaped deposits of sediment and rock debris found at the base of mountains, especially where ravines empty out not the lowlands


Naked cell of a diatom, which grows to full size and forms a new siliceous covering


A special feature or behaviour developed by organisms to help them survive in a particular environment.


All India Institute of Medical Sciences

Absolute dating

Determining the age of geological sample by calculations of radioactive decay and / or its position in relation to other samples

Active sonar

A device that generates under water sound from special transducers and analyses the returning echoes to gain information of geological, biological, or military importance


Asian Urban Research Association


Acadja: Land / water use and irrigation


Aquatic organisms, general


Allergy - An unusual reaction to a particular substance (allergen) which may be a food, pollen, an insect bite, a metal, a medicine, hair etc.


Abrasion - A minor wound resulting from the scraping or rubbing away of a small area of skin or mucous membrane.

axial corallite

axial corallite - a corallite which forms the tip of a branch.  Most Acropora have axial corallites whereas they only occur sporadically in otehr corals.


autotomy - a means of asexual reproduction by the break up of a parent polyp.

attachment scars

attachment scars - a scar-like patch on the central undersurface of free-living fungiids from where they were attached to teh substrate as juveniles


archaeocyaths - sponge-like metazoans that had skeletons.  They were mostly restricted to the Cambrian Era

arborescent colonies

arborescent colonies - colonies with a treee-like growth form

aragonite skeletons

aragonite skeletons - skeletons primarily composed of the aragonite form of calcium carbonate.  All Scleractinia have aragoniic skeletons



anastomose - descriptive term for branches which re-fuse after having initially divided


ampullae - the swollen part of a canal in skeleta Hydrozoa that hold medusae produced by internal fertilisation

ambulacral grooves

ambulacral grooves - grooves along the op of common walls between adjacent corallites

acolonial corals

acolonial corals  - Solitary corals that do not form colonies

azooxanthellate corals

azooxanthellate corals - corals that do not have zooxanthellate.  these are commonly found on reefs, but most are restricted to deep water, below the level of light penetration.


Acanthocauli - Juvenile corals (mostly Fungia) attached to the substrate either directly or on stalks.


Given a change of a single parameter, a readjustment of the physiology of an organism, reaching a new steady state


 Is the correctness of a measure when comparing to a known standard. See also resolution and precision.


Advection - The transport due to the mean flow

Arrested salt wedge

Arrested salt wedge -  A salt insrusion where the length is controlled by a balance between horizontal pressure gradients and hte friction on the interface.

Axial convergence

Axial convergence - The flow of water on teh surface of an estuary towards the middle from both sides.

Auxotrophic algae

Algae requiring a few organically derived substances, such as vitamins, along with dissolved inorganic nutrients for photosynthesis 

Autotrophic algae

  Algae capable of photosynthesis and growth using only dissolved inorganic nutrients


A variant of an enzyme type. These may be variants of a specific enzyme (e.g., cytochrome c) that are the products of a single genetic locus

Aggregated spatial distribution

A case where individuals in a space occur in clusters too dense to be explained by chance

Abyssal Gap

 A narrow break, in a ridge or rise, or separating two abyssal plains.

Abyssal Hills

 A tract of small elevations on the sea floo


A tributary river or brook 

Age of the Moon

 The interval in days and decimals of a day since the last New Moon.

Age of the Tide

Old term for the lag between the time of new or full Moon and the time of maximum spring tidal range.


A point in the sea where the tide has no amplitude. Co-tidal lines radiate from an amphidromic point and co-range lines encircle it.

Archipelagic Apron

A gentle slope with a generally smooth surface on the sea floor, particularly found around groups of islands or seamounts.

Arm of the Sea

A comparatively narrow branch or offshoot from a body of the sea

Artificial Harbour

A harbour where the desired protection from wind and sea is obtained from moles, jetties, breakwaters, etc. (The breakwater may have been constructed by sinking concrete barges, vessels, etc, to form a temporary shelter.)


A small atoll on the margin of a larger one

Automatic Tide Gauge

An instrument which measures and records the tidal data