Shingle or gravel shores, typically with sediment particle size ranging from 4 - 256 mm, sometimes with some coarse sand mixed in. This biotope is normally only found on exposed open coasts in fully marine conditions. Such shores tend to support virtually no macrofauna in their very mobile and freely draining substratum. The few individuals that may be found are those washed into the habitat by the ebbing tide, including the occasional amphipod or small polychaete. Situation: This unit often extends over the whole shore, sometimes extending into the subtidal zone. It may occur on the upper shore above A2.221, and in moderately exposed conditions, above unit A2.223 on the lower shore. Unit A2.211 may occur on the same shore as A2.111, where driftlines of algae and other debris accumulate on the upper shore. Temporal variation: There may be a temporary cover of the green seaweeds Enteromorpha spp. or Ulva spp. during periods of stability in the summer.