Data acquisition and field survey methods

Field recording and data management

The Marine Nature Conservation Review (MNCR) undertook a programme of field surveys throughout Britain between 1987 and 1998, collecting data suitable to develop the classification. In addition, data were acquired from the published literature and through collaboration with a wide variety of academic, government and other organisations. Comparable data were collected in Ireland through the BioMar project between 1992 and 1996.

The data comprise information on the nature of each site (such as substratum, wave exposure and height or depth surveyed), the type of sampling undertaken, the site's location and the species present (together with an indication of their abundance) within discrete habitats at the site. MNCR field recording techniques are described in Hiscock (1996), with Appendix 8 providing the guidance on how to complete MNCR field recording forms (the forms can be downloaded from here).The terminology relating to field survey methods is described further below, and should help users of the classification interpret the habitat information contained in the biotope descriptions. Procedural Guidelines for a wide range of field sampling techniques are given in the Marine Monitoring Handbook (Davies et al. 2001).

In total, data for over 16,000 sites comprising more than 36,000 habitat records from around Britain and Ireland were collated and entered onto the MNCR database (as described by Hiscock, 1996). The database includes a module which holds definitions of each classification type, linked to a national dictionary of marine species and to the field survey data. The field survey data have been made widely accessible via the web-based MERMAID application, and more recently, via the National Biodiversity Network from an MS Access-based 'relational' database, Marine Recorder. The Marine Recorder database application has been specifically developed to accept marine biological data from a wide range of survey techniques, including the data held originally in the MNCR database. The application can be downloaded here, and includes a dictionary of the habitat classification types.

Terms used for field recording and habitat definition

For semi-quantitative biological recording, the MNCR SACFOR scale was used.

The following definitions for physical habitat characteristics are taken from guidance notes for MNCR field recording (Appendix 8 in Hiscock ed. 1996). Some terms are modified for use in the classification.

Salinity - The categories are defined as follows (the points of separation approximate to critical tolerance limits for marine species):

*Fully marine*	30-40 ‰
*Variable*	18-40 ‰
*Reduced*	18-30 ‰
*Low*	<18 ‰

Wave exposure - These categories take account of the aspect of the coast (related to direction of prevailing or strong winds), the fetch (distance to nearest land), its openness (the degree of open water offshore) and its profile (the depth profile of water adjacent to the coast). Estimation of wave exposure requires inspection of charts and maps.

*Extremely exposed*	This category is for the few open coastlines which face into prevailing wind and receive oceanic swell without any offshore breaks (such as islands or shallows) for several thousand km and where deep water is close to the shore (50 m depth contour within about 300 m, e.g. Rockall).
*Very exposed*	These are open coasts which face into prevailing winds and receive oceanic swell without any offshore breaks (such as islands or shallows) for several hundred km but where deep water is not close (>300 m) to the shore. They can be adjacent to extremely exposed sites but face away from prevailing winds (here swell and wave action will refract towards these shores) or where, although facing away from prevailing winds, strong winds and swell often occur (for instance, the east coast of Fair Isle).
*Exposed*	At these sites, prevailing wind is onshore although there is a degree of shelter because of extensive shallow areas offshore, offshore obstructions, a restricted (<90o) window to open water. These sites will not generally be exposed to strong or regular swell. This can also include open coasts facing away from prevailing winds but where strong winds with a long fetch are frequent.
*Moderately exposed*	These sites generally include open coasts facing away from prevailing winds and without a long fetch but where strong winds can be frequent.
*Sheltered*	At these sites, there is a restricted fetch and/or open water window. Coasts can face prevailing winds but with a short fetch (say <20 km) or extensive shallow areas offshore or may face away from prevailing winds.
*Very sheltered*	These sites are unlikely to have a fetch greater than 20 km (the exception being through a narrow (<30o) open water window, they face away from prevailing winds or have obstructions, such as reefs, offshore.
*Extremely sheltered*	These sites are fully enclosed with fetch no greater than about 3 km.
*Ultra sheltered*	Sites with fetch of a few tens or at most 100s of metres.

In the habitat classification exposed (as in exposed littoral rock) encompasses the extremely exposed, very exposed and exposed categories, whilst sheltered (as in sheltered littoral rock) encompasses sheltered to ultra sheltered categories.

Tidal currents (or streams) (maximum at surface) - This is maximum tidal current strength which affects the actual area surveyed. Note for shores and inshore areas this may differ considerably from the tidal currents present offshore. In some narrows and sounds the top of the shore may only be covered at slack water, but the lower shore is subject to fast running water.

*Very strong*	>6 knots (>3 m/sec.)
*Strong*	3-6 knots (>1.5-3 m/sec.)
*Moderately strong*	1-3 knots (0.5-1.5 m/sec.)
*Weak*	<1 knot (<0.5 m/sec.)
*Very weak*	Negligible

In the habitat classification tide-swept habitats typically have moderately strong or stronger tidal currents.

Zone - These definitions primarily relate to rocky habitats or those where algae grow (e.g. stable shallow sublittoral sediments). For use of the terms infralittoral and circalittoral in the classification, especially for sediments, refer also to Table 5.

*Supralittoral*	Colonised by yellow and grey lichens, above the Littorina populations but generally below flowering plants.
*Upper littoral fringe*	This is the splash zone above High Water of Spring Tides with a dense band of the black lichen by Verrucaria maura. Littorina saxatilis and Littorina neritoides often present. May include saltmarsh species on shale/pebbles in shelter.
*Lower littoral fringe*	The Pelvetia (in shelter) or Porphyra (exposed) belt. With patchy Verrucaria maura, Verrucaria mucosa and Lichina pygmaea present above the main barnacle population. May also include saltmarsh species on shale/pebbles in shelter.
*Upper eulittoral*	Barnacles and limpets present in quantity or with dense Fucus spiralis in sheltered locations.
*Mid eulittoral*	Barnacle-limpet dominated, sometimes mussels or dominated by Fucus vesiculosus and Ascophyllum nodosum in sheltered locations. Mastocarpus stellatus and Palmaria palmata patchy in lower part. Usually quite a wide belt.
*Lower eulittoral*	Fucus serratus, Mastocarpus stellatus, Himanthalia elongata or Palmaria palmata variously dominant; barnacles sparse.
*Sublittoral fringe*	Dominated by Alaria esculenta (very exposed), Laminaria digitata (exposed to sheltered) or Laminaria saccharina (very sheltered) with encrusting coralline algae; barnacles sparse.
*Upper infralittoral*	Dense forest of kelp.
*Lower infralittoral*	Sparse kelp park, dominated by foliose algae except where grazed. May lack kelp.
*Upper circalittoral*	Dominated by animals, lacking kelp but with sparse foliose algae except where grazed.
*Lower circalittoral*	Dominated by animals with no foliose algae but encrusting coralline algae.

Substratum

*Bedrock*	Includes very soft rock-types such as chalk, peat and clay.
*Boulders*	Very large (>1024 mm), large (512-1024 mm), small (256-512 mm)
*Cobbles*	64-256 mm
*Pebbles*	16-64 mm
*Gravel*	4-16 mm
*Coarse sand*	1-4 mm
*Medium sand*	0.25-1 mm
*Fine sand*	0.063 - 0.25 mm
*Mud*	<0.063 mm (the silt/clay fraction)

Each division of sediment type above represents two divisions on the Wentworth scale (Wentworth 1922).

In the habitat classification, bedrock, stable boulders, cobbles or pebbles and habitats of mixed boulder, cobble, pebble and sediment (mixed substrata) as well as artificial substrata (concrete, wood, metal) are collectively referred to as rock. Highly mobile cobbles and pebbles (shingle), together with gravel and coarse sand are collectively referred to as coarse sediments. Mixed sediment consists of heterogeneous mixtures of gravel, sand and mud and may often have shells and stones also.