High energy infralittoral rock

Shallow water rock, below the tides, exposed to very strong waves and currents

Shallow water rock, below the tides, exposed to very strong waves and currents © Lin Baldock

On exposed rocky coastlines that are subject to strong waves or swift tidal currents, the shallow underwater environment (which may be exposed to the air on the lowest of tides) tends to be dominated by the large kelps and some smaller red seaweeds. 

The width of the kelp zone is all down to the amount of light penetrating the water.  Seaweed, like plants, needs sunlight to survive.  Where the water is very clear, this zone can be wide, reaching as far as an exceptional 45m deep.

Kelp does not establish in areas where the water movement is strongest or in surge gullies and caves, from which red seaweeds may also be absent in low light levels.  The rock walls in these areas are dominated by animal communities of sponges, sea squirts, sea mats, mussels and barnacles.  

Even where the kelp is present, there are large communities of animals.  Many small creatures including worms, crabs, sea snails and shrimp-like animals live in the holdfast by which the kelp attaches to the rock.  Kelp forests are also important for young fish.

This habitat is found on rocky coastlines, exposed to the full force of the prevailing south-westerly wind.

For the official habitat definition please see the documents listed below.

 

European distribution

Exposed rock below low water mark is found on the south-west and west coasts of Britain and Ireland, where they are exposed to the prevailing south-westerly wind.  They are also found on the north-east English coast.  In mainland Europe, they are associated with south and west facing rocky headlands and coastlines.

Shallow water rock, below the tides, exposed to very strong waves and currents fact

 

Official habitat definition

EUNIS habitat A3.1 Atlantic and Mediterranean high energy infralittoral rock

 

Further information

JNCC Marine Habitat Classification

JNCC EUNIS habitat correlations table