Low energy intertidal rock

Rocky seashores, sheltered from waves and currents

Some rocky shores can be found in areas sheltered from prevailing winds and subject only to weak tidal streams.  The beach can be made up of bedrock or of boulders, cobbles and pebbles, which may lie on a mixture of sand and mud. 

The low energy of this environment allows marine plants to flourish, and the most obvious feature of many of these shores is the dense blanket of brown seaweeds, formed by members of a family known as the wracks.   

On closer inspection, different wracks occur in zones down the shore, as the area preferred by each type of seaweed depends on the length of time it is uncovered by the falling tide.  The channelled wrack, which has branched, fleshy ends to its leaf-like fronds occurs high up on the shore.  The familiar bladder wrack, with its ‘bubblewrap’-like rounded air bladders, is found in the mid shore, and the rough-edged toothed wrack near the low tide mark.  Sometimes on very horizontal shores with a small tidal range, the zones overlap. 

Seaweeds need a hard substrate to anchor to with their ‘holdfasts’, which is why the wracks like rocky shores.  Smaller seaweeds will, in turn, use the wrack to grow on.  Animals associated with the seaweeds include the colourful flat periwinkle, which is well camouflaged, as it resembles the air bladders on the bladder wrack.  Beds of mussels are also common on sheltered rocky shores.

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


European distribution

Sheltered rocky and boulder shores are found around most of the British coast, where there is shelter from the prevailing south-westerly wind.  In mainland Europe, they are associated with inlets, lochs, estuaries and sheltered bays.


Official habitat definition

EUNIS habitat A1.3 Low energy littoral rock


Further information

JNCC Marine Habitat Classification

JNCC EUNIS habitat correlations table

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