Biodiversity & Conservation

MarLIN Glossary

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O

Ob
In north-west Scotland - a small (generally < 1 km), relatively shallow (generally < 10 m) ice-gouged basin, almost completely enclosed by surrounding land and connected to the sea by a generally intertidal sill and/or pass. The main body does not dry out at low tide (based on Earll & Pagett, 1984 and Smith, 1987.)

Ocean
1) The body of salt water that covers more than 70% of the Earth's surface. 2) A very large stretch of sea, especially one of the five oceans of the world, as delineated by definable and independent land contours, bottom topography and wind and water circulation in both horizontal and vertical planes (based on Charton & Tietjen, 1989).

Oceanodromous
Used of organisms that migrate only within the oceanic province (Lincoln et al., 1998).

Oceanography
The branch of science dealing with the physical, chemical, geological and biological features of the oceans and ocean basins (from Makins, 1991).

Ocelli
Eye-like markings (Abercrombie et al., 1973).

Oligohaline
Pertaining to brackish water between 0.5 ‰ and 5 ‰ salinity (based on Carriker, 1967, in McLusky, 1993).

Oligotrophic
Having low primary productivity; used of water bodies or substrata low in nutrients.

Omnivores
Animals which feed on a mixed diet including plant and animal material (from Lincoln et al.,1998).

Ontogenetic Migration
The occupation by and animal of different habitats at different stages of development (Lincoln et al.,1998).

Oogamous
Having large, non-motile eggs and small motile sperm. Usually applied to algae (Lincoln et al., 1998).

Open Coast
Any part of the coast not within a marine inlet, strait or lagoon, including offshore rocks and small islands (Hiscock, 1990).

Operculum
1) In Gastropoda a horny plate, sometimes strengthened with calcareous material, carried on the foot of gastropods that closes the shell aperture when the animal retracts into its shell (Graham, 1988). 2) In unstalked barnacles, the moveable lid-like structure used to close the aperture (Stachowitsch, 1992). 3) In Bryozoa a generally uncalcified, hinged or pivoted flap or lid-like structure, which closes the orifice through which the feeding tentacles are extended and retracted. 4)In fish, the cover over the gill-slits.

Opossum Shrimp
The common name for members of the Order Mysida (Phylum Arthropoda, Subphylum Crustacea). Cf. mysid.

Opossum Shrimps
Plural of 'opossum shrimp'.

Organochlorine
A synthetic organic compound containing chlorine, highly toxic and the base for many pesticides. Includes PCBs (polychlorinated biphenyls).

Organotin
A synthetic organic compound containing tin, used as a pesticide particularly to prevent the establishment of fouling organisms, but known to be toxic to certain species even at low concentrations. See 'imposex'.

Ovicell
A globular brood chamber in Cheilostomatida Bryozoa (Hayward & Ryland, 1998).

Oviger
Singular of 'ovigers'

Ovigerous Leg
See 'ovigers'.

Ovigers
In Pycnogonida, the third pair of appendages, less well developed than legs, and consisiting of up to 10 segments. The oviger (or ovigerous leg) serves to carry the egg mass in females but is reduced in males (Stachowitsch, 1992).

Oviparous
A type of reproduction in animals in which the fertilized eggs are laid or spawned by the mother.

Ovoviviparous
A type of reproduction in animals in which the embryo(s) develop in persistent membranes and hatch within the maternal body. No nutrition is derived from the mother.

Oxycline
A horizontal boundary layer in the water column, at which dissolved oxygen content changes sharply with depth.

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Glossary references