Tideswept channels

The tidal streams that flow through the sounds and channels of Scotland's complex coasts breathe life into the seabed, bringing food and oxygen to nourish abundant sealife.

What is so special about them?

From gentle drifts to raging maelstroms, shallow gravel to deep bedrock, tideswept channels can be 'hotspots' for marine life - places where the tidal currents and topography result in complex seabeds supporting a diverse range of animals and plants.

Where do they occur?

Strong tidal streams result from a constriction in the coastline - such as at the entrance to sealochs, between islands, or between islands and the mainland. Fine, muddy particles are carried away, leaving seabeds of coarse materials - gravel, pebbles and boulders - and bedrock, 'sandblasted' in places by sand and gravel.

In shallow water, seaweeds thrive in strong currents. On bedrock and boulders, kelps and sea oak (Halidrys siliquosa) grow very long, with big, colourful sponges wrapped around their bases. A characteristic range of red, green and brown seaweeds grow on pebbles and shells in sand and gravel, sometimes in dense meadows. There may also be patches of eelgrass and maerl, together with burrowing anemones and tubeworms while molluscs and urchins lie buried beneath

Below 15 - 20 m, where there is less light for seaweeds to grow, animals dominate. On bedrock and boulders where tidal currents are too strong for grazing urchins to cling on, a dense animal 'turf' of sea mosses, anemones, sponges and barnacles may completely cover rocks, while large brown and velvet crabs occupy crevices. Dense beds of brittlestars often cover the channel base, while horse mussels and flame shells  may create their own living reefs inhabited by a multitude of other small creatures - a good feeding ground for juvenile fish.

What is the status of this habitat in Scotland?

Historically tideswept channels have been refuges from human activities. However, this situation is changing with the development of the marine renewables industry in Scotland. The proposed leasing of areas of seabed within the Pentland Firth, one of our best known tideswept channels, has attracted considerable interest from developers wishing to explore the potential for tidal stream energy generation.

Are we doing anything to look after tideswept channels in Scotland?

Tideswept channels are a priority UK Biodiversity Action Plans   habitat, now taken forward by the Scottish Government as part of the Scottish Biodiversity Strategy.  This habitat is an Scottish Natural Heritage priority for marine conservation action ('Priority Features' work programme) and will be subject to new protection efforts deriving from the Scottish Marine Bill  (incl. Marine Spatial Planning and new Marine Protected Areas).