information on the biology of species and the ecology of habitats found around the coasts and seas of the British Isles

MarLIN Glossary


See 'Environmental Assessment'.


Outgoing or falling tide.


A plant or animal form produced in response to particular habitat factors, the characteristic adaptations not being heritable; a habitat form (from Lincoln et al., 1998).

Ecological Quality

An expression of the structure and function of the ecological system taking into account natural physiographic, geographic and climatic factors as well as biological, physical and chemical conditions including those resulting from human activities (from a draft of the EC Ecological Quality of Water Directive) .

Ecological Quality Objective

The desired level of Ecological Quality (EcoQ) relative to a reference level.


The study of the inter-relationships between living organisms and their environment (from Lincoln et al., 1998).


See 'Ecological Quality'.


See 'Ecological Quality Objective'.


A community of organisms and their physical environment interacting as an ecological unit (from Lincoln et al.1998). Usage can include reference to large units such as the North Sea down to much smaller units such as kelp holdfasts as "an ecosystem".


The zone of transition between two major ecological communities.


See 'ectoparasitic'.


Parasitic on the outer surface of its host (adapted from Lincoln et al., 1998).


Motion of a fluid in directions differing from, and at some points contrary to, the direction of the larger-scale current (from Allaby & Allaby, 1990); a circular movement of water, the diameter of which may be anything from several cm to several km, caused by topographical features or sudden changes in tidal or tidal stream characteristics (Based on Ministry of Defence, 1987). Cf. 'gyre'.


Environmental Impact Assessment, cf. Environmental Assessment.


A type of marine inlet typically where the line of the coast follows a concave sweep between rocky headlands, sometimes with only a narrow entrance to the embayment.

enclosed coast

A marine inlet or harbour fully enclosed from the open sea except at the entrance, not normally open to the sea at two ends. The connection with the open sea is normally less restricted than is the case with lagoons (based on Hiscock, 1990.)


Partially or totally covered with a hardened crust (OED, 2008).


To cover with a crust or thin coating (OED, 1990).


IUCN Red List categories - a taxon is considered Endangered when it is not Critically endangered (q.v.) but is facing a very high risk of extinction in the wild in the near future (International Union for the Conservation of Nature and Natural Resources 1994) (cf. 'Extinct', 'Critically endangered', 'Vulnerable').


Referring to organisms that are confined to a particular area or geographical location (Prescott , 1969).


The complex of biotic climatic, edaphic and other conditions which comprise the immediate habitat of an organism; the physical, chemical and biological surroundings of an organism at any given time. (cf. 'habitat') (from Lincoln et al. , 1998).

Environmental Assessment

A process of predicting and evaluating an action's impacts on the environment, from which the conclusions are used as a tool in decision-making. It aims to minimize environmental degradation by giving decision-makers better information about the consequences which development actions could have on the environment, although it cannot, in itself, achieve that protection (based on Pritchard, 1993). An Environmental Assessment can be used to produce an Environmental Statement (ES). Cf. 'Environmental Statement' 'Strategic Environmental Assessment'.

Environmental Impact Assessment

See 'Environmental Assessment'.

Environmental Statement

A statement intended to provide all of the information needed to evaluate the likely environmental implications of a proposed development (adapted from Treweek, 1996). Cf. 'Environmental Assessment (EA)'.


Living on the surface of the seabed.


All organisms living on the surface of the seabed.


Living attached to the surface of another organism, without any detriment or benefit to the host (Lincoln et al., 1998).


Animals living on the surface of the seabed.


Adjective form of 'epifauna'.


Plants living on the surface of the substratum.


Adjective form of 'epiflora'.


Growing on the surface of rock.


The oceanic zone extending from the surface to about 200 meters (Abercrombie et al., 1973).


Living at the sediment/water interface (Lincoln et al., 1998).


Growing on the surface of a living plant (but not parasitic upon it).


Attached to sand particles (Lincoln et al., 1998).


An individual that arises by modification and separation from the posterior end of the worm in order to leave the bottom and reproduce (adapted from Rouse & Pleijel, 2001). For instance, the new individual grows from the posterior segment and upon separation the daughter generates a new head and the mother a new posterior end.


Reproducing by epitoky (see epitoke).


Growing or living on the exterior of a living animal (but not parasitic upon it).


See 'Environmental Statement'.


a depressed area, behind the beaks in some bivalves, in the dorsal line (about and behind the ligament if external), in one or both valves, and generally set off from the rest of the shell by a change in sculpture or colour (Tebble, 1976).


1) A semi-enclosed coastal body of water which has a free connection with the open sea, and within which sea water is measurably diluted by fresh water derived from land drainage (Pritchard 1967). This is the definition used in the context of the MNCR. 2) An inlet of the sea reaching into a river valley as far as the upper limit of tidal rise (Fairbridge, 1980). (This definition includes freshwater tidal areas, excluded by Pritchard (1967).) (See Davidson et al., 1991 and McLusky, 1993 for discussion of definitions.) Three main types of estuary are recognised: a) Coastal plain estuaries, formed by the flooding of pre-existing river valleys. Maximum depth in these inlets is usually less than 30 m, with a large width-to-depth ratio; b) Bar-built estuaries: also partially-drowned river valleys, with a characteristic sediment bar across their mouth; c) Complex estuaries: river estuaries formed as a result of a range of influences such as geological constraints from hard rock outcrops, glaciation, erosion, and sea-level change. See also 'marine inlet'. For the purposes of the EC Habitats Directive, 'estuaries' are defined as: "Downstream part of a river valley, subject to the tide and extending from the limit of brackish waters. River estuaries are coastal inlets where, unlike 'large shallow inlets and bays' there is generally a substantial freshwater influence. The mixing of fresh water and sea water and the reduced current flows in the shelter of estuaries leads to deposition of fine sediments carried in from the sea and down rivers, often forming extensive intertidal sand and mud flats. Where the tidal currents are faster than flood tides, most sediments deposit to form a delta at the mouth of the estuary" (European Commission 1995).


Fully saline seawater >30 ‰ salinity.


The main part of the littoral zone characterized by limpets, barnacles, mussels, fucoid algae (other than those characteristic of the littoral fringe), with red algae often abundant on the lower part. It lies above the main population of Laminariales. Zonation within the eulittoral is variable, with two to four (commonly three) belts often clearly discernible. 1) (lower) The lower belt of the eulittoral subzone, bordering the sublittoral fringe, and generally dominated by Fucus serratus and red algae. 2) (mid) The broad middle belt of the eulittoral subzone, usually characterized by limpets and barnacles or Mytilus and filamentous red algae in exposed situations, or dominated by fucoids, often with clumps of large mussels present, in shelter. 3) (upper) The narrow upper belt of the eulittoral subzone, often very variable in character. (from Hiscock , 1990).


Of or relating to the capability of an organism to live in environments of variable salinity (from Charton & Tietjen, 1989).


Of or relating to the capacity of some organisms to survive in a wide range of temperatures (from Charton & Tietjen, 1989).


The over-enrichment of an aquatic environment with inorganic nutrients, especially nitrates and phosphates, often anthropogenic (e.g. sewage, fertilizer run-off), which may result in stimulation of growth of algae and bacteria, and can reduce the oxygen content of the water.


In conservation assessment - in identifying sites for protection, preference will be given to sites with larger examples of highly rated or rarer biotopes. It is also necessary to consider the size of site required to ensure that the unit to be managed is 'viable'.


IUCN Red List categories - a taxon is 'extinct' when there is no reasonable doubt that the last individual has died (International Union for the Conservation of Nature and Natural Resources 1994). The term can be applied on a local or national basis as well as world-wide and is also used to refer to situations where it no longer exists from a particular point of view (for instance: 'functionally extinct'; 'commercially extinct'). Cf. 'Critically endangered', 'Endangered', 'Vulnerable'.

extremely exposed

Of wave exposure - open coastlines which face into the prevailing wind and receive both wind-driven waves and oceanic swell without any offshore obstructions such as islands or shallows for several thousand kilometres and where deep water is close to the shore (50 m depth contour within about 300 m) (from Hiscock, 1990).

extremely sheltered

Of wave exposure - fully enclosed coasts with a fetch of no more than about 3 km (from Hiscock, 1990).