Communities of Atlantic littoral rockpools

Rockpools occur where the topography of the shore allows seawater to be retained within depressions in the bedrock producing pools on the retreat of the tide. As the associated communities are permanently submerged they are not directly affected by height on the shore and normal rocky shore zonation patterns do not apply. Factors such as pool depth, surface area, volume, orientation to sunlight, shading, internal topography, sediment content and type, together with wave exposure, shore height, and hence flushing rate, and the presence of absence of freshwater runoff, results in large spatial variation in community structure, even between adjacent pools at the same shore height.

Shallow rockpools in the mid to upper shore are characterised by encrusting coralline algae and Corallina officinalis. Deeper rockpools on the mid to lower shore can support fucoids and some sublittoral species such as kelp. Those rockpools influenced by the presence of sand are characterised by sand-tolerant seaweed such as Furcellaria lumbricalis and Polyides rotundus. Where more stable sand occurs in the base of the rockpool sea-grass beds can occur. Shallow rockpools on mixed cobbles, pebbles, gravel and sand may be characterised by hydroids. A very rough guideline to the terms shallow and deep rockpools: shallow rockpools do not support kelp, whereas deep rockpools do. Rockpools on the upper shore which are subject to rainwater influence and wide fluctuations in temperature are not included in this habitat type. This habitat also does not include shallow standing water on compacted sediment or mixed substrata.

Indicators of quality:

Both biotic and abiotic indicators have been used to describe marine habitat quality. These include: the presence of characteristic species as well as those which are sensitive to the pressures the habitat may face; water quality parameters; levels of exposure to particular pressure, and more integrated indices which describe habitat structure and function, such as trophic index, or successional stages of development in habitats that have a natural cycle of change over time.

There are no commonly agreed indicators of quality for this habitat, although particular parameters may have been set in certain situations e.g. protected features within Natura 2000 sites, where reference values have been determined and applied on a location-specific basis.

Synthesis of Red List assessment

Confidence in the assessment

Pressures and threats