Layout and components of biotope descriptions

Descriptions for each unit in the classification, from broad habitats to sub-biotopes, are laid out as follows:
A unique letter code, reflecting the level of the described type within the classification hierarchy. A "breadcrumb trail" of codes is shown in the standard classificaiton colour scheme, which indicates what level of the biotope classification is being currently looked at, and allows a direct link to the "parents" of the type currently being looked at.
The title gives the key biological and physical features of the type, with emphasis on the features which help to distinguish it from closely related types of the same level in the hierarchy. The habitat part of the title usually includes the zone, substratum and another key habitat factor. To avoid becoming overly clumsy the titles do not cover all habitat characteristics or characterising species, and common names are not given (although they are given in the text description).
NOTE: It is very important to refer to the full description and to the habitat matrices to determine the full nature of the type and not to rely on the title alone.
Habitat characteristics   
The typical habitat characteristics of the type for salinity, wave exposure, tidal currents, substratum, zone, height or depth band and, where appropriate, other factors critical to that particular type. The range given for each factor tends to be broader for higher types and more tightly defined for lower types. When assigning samples to types, it should be noted that in some cases the type may occur outside the range given (see profiles given in the comparative tables which show that a small proportion of records may occur outside the typical range for the type), though care should be taken to ensure that another type has not been described to cover the example being considered. All heights and depths are corrected to chart datum.
Previous code                 
Codes used in versions 6.95, 96.7, and 97.06 (Connor et al. 1995 a, 1996, 1997 a, b) are given where different to the current code. Where communities from previous versions have been combined or split, previous codes are shown as far as possible. Some communities in the revised classification are newly defined and may not relate directly to types in the previous classification. Lookup tables which help to translate 2004 to 1997 codes (and vice versa) are available to download in the form of an Excel™ spreadsheet from the main download page.
Distribution map
A distribution map is included, showing the location of field survey records assigned to the biotope on the JNCC marine database. The red dots show the location of core biotope records, i.e. those records on which the biotope description is based (see data analysis for details). Blue dots show other certain records of the biotope, whilst black dots denote uncertain records of that biotope (i.e. field records that have been tentatively assigned to the biotope - they may not match the description fully, or they may be incomplete records). Note that the distribution maps only show those records that are held on the JNCC marine database, and therefore do not reflect the full extent of the biotope. 
An account of the general nature of the habitat and community characteristics, and its micro-habitat features (e.g. crevices, under-boulders, kelp stipes) if present.
Describes the general situation on the shore or in the sublittoral, in relation to other types (i.e. along gradients of substratum, zonation, wave exposure, tidal currents, salinity etc.).
Temporal variation        
This section outlines the known natural temporal dynamics of the type described, such as seasonal changes in community structure or physical environment. In general, much more information is needed for this section. In some cases separate types may have been defined because there is a lack of knowledge that the communities are temporal variations within a single habitat type.
Similar types                  
Attention is drawn to similar types which should be considered before assigning a field record to a particular biotope. The main similarities and principal distinguishing features are described for each similar biotope, and the codes are hyperlinked directly to the relevant descriptions.
Characterising species           
A list of those species which contribute most to the overall similarity between core records assigned to the type, i.e. characterise the type, with associated information on their frequency of occurrence, their individual contribution to the similarity within the core data set of records, and the typical abundance at which they occur.
For each type, characterising species have been determined using the SIMPER routine in PRIMER (Clarke & Warwick, 2001). For a given set of records (in this case, core records of each type), SIMPER indicates and ranks the individual contribution of each species to the overall similarity within the data set. Both the frequency of occurrence of each species within the dataset and their abundance (using the SACFOR abundance scale) for epifaunal data and numeric counts for infaunal data) are taken into account during this process.  Species that contribute more than 1% to the overall similarity of the records within the data set are defined as 'characterising species', and listed in a characterising species table. Those that contribute less that 1% are not listed. Species which qualify according to the SIMPER routine, but are Present or Rare on the MNCR SACFOR scale and present in fewer than 20% of the records, are occasionally excluded from the characterising species table.
Care has been taken to mention each of the characterising species in the descriptions for each type. Sometimes additional species are mentioned that are particularly indicative (faithful) of that type or characteristic of a biogeographic region, but which have not qualified as 'characterising species' according to the SIMPER routine.
Some of the biotope descriptions, especially in the sublittoral sediment section, have been based on a mixture of epifaunal (semi-quantitative) and infaunal (quantitative) sample data. In these cases, separate SIMPER analyses were carried out for the two types of data, and the outcome was combined into a single characterising species table. Where there is overlap between species recorded in the epifaunal and infaunal data, there are duplicate entries for species: the entries relating to the infaunal datasets have figures for "numbers per metres squared", whereas entries relating to epifaunal datasets only have SACFOR entries.
The % contribution to similarity column of the table shows the contribution of each characterising species to the similarity within the type, i.e. the higher the contribution, the higher the importance of the species. The number of species in the table reflects the species diversity within each type. In types with a high species richness, a large number of species each contribute with a relatively low amount to the similarity within the group. If a type has low diversity, then a small number of species contribute with relatively large amounts to the overall similarity and hence fewer species are listed in the table. In a few cases, a long species list indicates low overall similarity of records within the type.
The % frequency of occurrence column of the table shows the occurrence of a species within a certain biotope. The symbols represent percentage occurrence in the samples as follows:
                  Occurs in 81-100% of the records for the type
                  Occurs in 61-80% of the records for the type
                  Occurs in 41-60% of the records for the type
                   Occurs in 21-40% of the records for the type
The typical abundance column of the table shows the mean SACFOR abundance for each characterising species within the samples where it is present. Quantitative infaunal counts have been converted to the SACFOR scale for compatibility of data presentation. For types where the core records are exclusively quantitative infaunal records (e.g. most of the littoral sediment types), an additional column is included in the characterising species table, showing mean counts per m2 for each species within the core data set.
Example photographs
Where they are available, up to three photographs are shown to illustrate the appearance of the biotope in the field.