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Marine Habitat Classification


This section contains useful tools and background information about the marine habitat classification system.

How to use the classification

This PDF guide is the best place to start to understand the classification. It includes:

  • The layout and components of each biotope description
  • Guide to understanding the biotope codes
  • Explanation of the species nomenclature

How to assign biotopes

How to interpret survey data and assign a biotope using the classification, or EUNIS. This document provides a step by step guide to reviewing evidence, suggestions for dealing with common problems, and a template biotope report structure.

Tools to help assign biotopes

Comparative tables

The comparative tables enable a rapid comparison of the species composition and the principal physical characteristics between user-defined sets of biotopes (and other classification units). There are no tables for the deep-sea section added in 2015; therefore they are only relevant to littoral and sublittoral zones - equivalent to version 04.05 of the classification. The tables are provided in the form of two downloadable Excel documents. One contains physical data, and the other contains biological (species) data. The comparative table for the new version 22.04 are still under development and will be available to download soon.

Habitat matrices

The habitat matrices document contains a series of diagrams that visualise the biotopes in relation to various abiotic conditions.

  1. The primary habitat matrices provide a general framework for the classification and shows the level 2 and 3 types.
  2. For each of the broad habitats in the shallow section of the classification (LR, LS, IR, CR, SS) more detailed matrices provide a rapid indication of the range of biotopes and sub-biotopes(levels 5 & 6) that could occur under certain habitat conditions, e.g. moderate energy infralittoral rock or intertidal sandflats. They can be used to indicate which closely related biotopes should be considered before determining to which type a sample record should be assigned.
  3. The habitat matrices for the new version 22.04 are still under development and will be available to download soon.

Classification hierarchy and full biotope list

To help navigate the classification hierarchy, a full biotope list and hierarchy structure diagrams (one for each broad habitat) are available to download (xlsx).

Correlation tables

Using the correlation tables, you can identify possible relationships between habitats in the Marine Habitat Classification for Britain and Ireland, the marine section of the EUNIS classification and those listed as being important for conservation under various legislative instruments (e.g. Annex I habitats, OSPAR habitats). The correlation tables are periodically revised as habitat definitions are refined.

Two tools are available to investigate these correlations: the correlation spreadsheet and the correlation database. These two tools contain the same correlations presented in two different ways.

The current correlation table and database do not include the new Marine Habitat Classification for Britain and Ireland version 22.04. The tables are currently under development and will be available soon.

IMPORTANT: note that habitat correlation tools give an indication of which biotopes may be classed as a listed habitat, but remember that additional specific criteria may apply (e.g. the habitat may have to be a certain size) so you should always check detailed listed habitat definitions to make sure. 

Correlation tables: database version

Correlation tables: spreadsheet version

Propose a new or revised biotope

Have you found a community that doesn’t sit well within any existing biotopes in the Marine Habitat Classification for Britain and Ireland? Please let us know at and refer to the guidance below.

Current developments

The classification is a work-in-progress. Read the summary for an update on the ongoing work to update the classification.


Version 22.04

The update to version 22.04 involved the addition of five new biotopes and revision of some existing biotopes in the Sublittoral Sediment section of the classification. Edits to biotope codes as a result of species name changes were made to the whole classification where applicable. The report for this version is still under development and will be published soon but see this document for a summary of the changes.

Version 15.03

The update to version 15.03 saw the addition of a deep-sea section for the first time; this report describes the work done to create this new section. No edits were made to the rest of the classification.

Version 04.05

The update to version 04.05 involved the additional of new biotopes and revision of some existing biotopes. This report gives a useful background and description of version 04.05 classification, which is still just as relevant to the littoral and sublittoral sections of version 15.03.

Version 97.06

An early version of the classification, described in these two reports (see the Correlation tables for the relationship between version 97.06 and the current version of the classification).

Version 96.7

  • Connor, D.W., Brazier, D.P., Hill, T.O., Holt, R.H.F., Northen, K.O., & Sanderson, W.G. 1996. Marine Nature Conservation Review: marine biotopes. A working classification for the British Isles. Version 96.7. Peterborough, Joint Nature Conservation Committee.

Version 6.95

  • Connor, D.W., Hiscock, K., Foster-Smith, R.L., & Covey, R. 1995. A classification system for benthic marine biotopes. In: Biology and ecology of shallow coastal waters. Proceedings of the 28th European Marine Biology Symposium, ed. by A. Eleftheriou, A.D. Ansell & C.J. Smith, 155-165. Fredensborg, Olsen & Olsen.


SACFOR abundance scale

The SACFOR abundance scales adopted from 1990 provide a unified system for recording the abundance of marine benthic flora and fauna in biological surveys. It has been used to describe the relative quantities of taxa in many of the biotope descriptions.

MNCR recording forms

Central to all field surveying during the Marine Nature Conservation Review of the 1990s was a series of specifically designed recording forms onto which field data were transcribed. These are still used by field surveyors today for in situ shore and dive surveys.

  • Guidance (PDF, 67 Kb) notes for completion of MNCR recording forms
  • Survey form (PDF, 23 Kb) - For general details about the entire survey including the organization and personnel involved, the dates and general location of the survey and the range of methods used
  • Site form (PDF, 40 Kb) - for information on the main features of each site, including its name and position, the surveyors, the time and type of survey undertaken, general physical characteristics, uses and impacts
  • Habitat forms – There are two habitat forms, one for littoral habitats (PDF, 60 Kb) and one for sublittoral habitats (PDF, 78 Kb). They are for details of the physical and biological nature of the habitat and include a checklist of species against which to record abundance [species names updated in July 2017].


 The references cited in the biotope descriptions are available in this reference list.

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