Scientific Glossary

Glossary of terms and abbreviations relevant to the International Seabed Authority and the documents it produces

Please note that this is a constantly evolving document.

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Title
Macrobenthos	The macrofauna that is found in the benthic environment. Dominated by polychaetes. Often synonymous with macrofauna.
Macrofauna	Animals which are smaller than 2cm but are retained on a sieve of mesh size 250µm. Positioned in size between the meiofauna andmegafauna. Dominated by polychaetes.
Madeira Abyssal Plain	An abyssal plain in the Atlantic Ocean, approximately 1000km west of North Africa. It is approximately 5400m deep. Abbreviated to MAP.
Magma	Molten rock below the Earth's surface.
Manganese Nodule	Synonymous with polymetallic nodule.
MAP	Madeira Abyssal Plain.
MAST	Marine Science and Technology (EU programme).
Mega Core	Sample taken with a mega corer.
Mega Corer	A larger version of the multi corer capable of sampling macrofauna in addition to meiofauna and microfauna. Takes a smaller sample than the box corer but there is less disturbance of the surface sediment.
Megabenthos	The megafauna that is found in the benthic environment. Often synonymous with megafauna.
Megafauna	Defined as animals larger than 2cm. These animals can be observed from photographs. The largest size class of animals. Comprised of errant and sessile organisms.
Meiobenthos	The meiofauna that is found in the benthic environment. Dominated by the nematoda and benthic copepoda. Often synonymous withmeiofauna.
Meiofauna	Animals that are intermediate in size between macrofauna and microfauna. Operationally defined as organisms which pass through a sieve of mesh size 250µm but are retained on a mesh size of 32µm. Dominated by the foraminifera, copepoda and nematoda.
Meroplankton	Temporary members of the plankton, usually during their early life stages, but not as adults. Compare to holoplankton.
Mesopelagic	Referring to the portion of the oceanic province that is below the epipelagic and above the bathypelagic, usually corresponding to the dimly lit ocean or "twilight zone". This zone contains an oxygen minimum zone and usually the maximum concentrations of the nutrients nitrate and phosphate. {Figure}.
Metazoan	Multicelled animals.
Meteorological	Pertaining to meteorology.
Meteorology	The science and study of the physics, chemistry, and dynamics of the Earth's atmosphere, especially weather and climate.
Micro-organism	Microscopic organisms including bacteria, archaea and microscopic eukaryotes.
Microbenthos	The microfauna that is found in the benthic environment. Often synonymous with microfauna.
Microbial	Pertaining to microbes.
Microfauna	Organisms invisible to the naked eye, smaller than meiofauna. Operationally defined as organisms which pass through a sieve of mesh size 32µm.
Mid-Ocean Ridge	A bilaterally symmetrical submarine ridge with sloping sides produced as two tectonic plates move apart from each other. Almost always associated with hydrothermal activity and the formation of polymetallic sulphides.
Mini Core	Sample taken with a mini corer.
Mini Corer	A smaller version of the multi corer.
Mir I	Russian Deep-Sea Research Vehicle. Rated to a depth of 6000m. Sister vessel of Mir II.
Mir II	Russian Deep-Sea Research Vehicle. Rated to a depth of 6000m. Sister vessel of Mir I.
Molecular Operational Taxonomic Unit	A taxonomic unit defined using the DNA of an organism rather than it's morphology. Ideally it is at the species level. Abbreviated toMOTU.
Morphological	Pertaining to morphology.
Morphology	Form and structural features. Can be used to describe organisms and geological features amongst other things.
Motility	The ability to move.
MOTU	Molecular Operational Taxonomic Unit.
Multi Core	Sample taken with a multi corer.
Multi Corer	A quantitative sediment sampling device suitable for sampling soft sediment. Less disturbance of the surface sediment than a box corer. Takes simultaneous tube core samples to a depth of up to approximately 30cm. Most often used for sampling meiofauna andmicrofauna. Also used for chemical sampling of soft sediment. Also called a multiple corer. Smaller and larger versions sometimes called a mini corer and mega corer respectively.
Multiple Corer	Synonymous with multi corer.