Natural England - Broad habitats

Broad habitats

A habitat is the place and conditions in which a plant or animal lives, and central to the definition of a particular habitat are the physical characteristics of the location. How warm, deep or salty the water is are important factors, as is the type of substrate – whether the seabed is rock, sand, gravel, mud or a mixture. Whether the site is exposed to strong waves and currents or is in a sheltered location is also influential.

The range of physical conditions that can be tolerated varies for different animals and plants. Some are found in only a few places with optimum conditions, while others are less specialised and can live successfully in a wide variety of habitats. Certain marine life can dominate a particular type of seascape, which then further influences the other animals and plants found there and adds a biological element to the definition of the habitat.

The variety of marine habitats around the British coast explains why there is such diversity of life in our waters.

Scientists have a classification system for marine habitats, and have developed some specialist terms to describe the different depth zones in which particular habitats are found. Depth has a very strong influence on marine life – there will be quite different communities living at the different heights on the beach, and these will all be distinct from those in shallow, mid-depth and very deep water.

The terms ‘littoral’ and ‘intertidal’ mean on the shore, and describe the zone where the marine life is alternately exposed to the air and covered (or at least splashed) as the tide comes in. The ‘sublittoral’ or ‘subtidal’ zone begins at the very bottom of the shore, which is only uncovered on the very lowest tides. The coastal subtidal area is then further divided into two distinct zones. The ‘infralittoral’ is the shallowest, and is dominated by plants and seaweeds. Below this, where there is insufficient light for most plants and seaweeds to grow, is the ‘circalittoral’ in which marine animals dominate. Deep-sea habitats are again very different as it is totally dark and unaffected by surface waves and currents, but communities of specially adapted animals are still found here.