Kelp species

In almost any coastal area of Europe where there is a suitable substratum (rock, boulder, cobble, artificial substrata) and adequate water quality, one or more species of kelp may be found. On the western coasts of the UK, the geological conditions result in a complexity of bays and headlands, rocky shores and cliffs, offshore islands and islets, intertidal and submerged reefs which are ideal for the development of kelp forests. With the exception of heavily silt-loaded estuarine areas, all subtidal, stable rock substrata within the photic zone of northern Europe are likely to be colonised by kelp. On the Eastern coasts of the UK, in particular from the Thames estuary to the Ouse estuary, and in the southern parts of the North Sea, the coasts are mostly either depositional shores or are formed of friable rock, unsuitable for kelp attachment and so distribution is sporadic at best. Further north, as rocky shores become more prevalent once again, kelp beds reappear along the coasts. In the north west of Scotland, particularly around the Hebrides where the habitat is especially suitable with gently shelving rocky basins between many of the islands, the kelp forests cover an enormous area of the subtidal seabed with L. hyperborea being the dominant kelp. Kelp beds of a similar extent are found on the coasts of Brittany, where the dominant species is L. digitata.

There are at present 13 species (confirmed) of kelp found in European waters of which two are introduced aliens which have escaped from cultivation. Of the remaining species, 4 have a northern (boreal) distribution and 4 have a southern distribution, while the other 3 species are found in both northern and southern waters (see table below). There is some debate as to the validity of the species of Laminaria in the simplices group (L. saccharina). In northern waters (Scotland and the Faeroes) there are kelp plants that have been identified as L. longicruris and L. faroensis. However, other authors regard these as local growth forms of L. saccharina. For the purposes of this review, the debatable species will be considered as forms of L. saccharina.

An excellent review of the history of the evolution of the marine benthic flora and its distribution patterns can be found in Lüning (1990, chapter 2). The relatively large numbers of different kelp species found in European waters are the result of the pattern of tectonic activities and the development of oceanic circulation patterns over the last 15 million years. As a result, we now have, within European waters, kelp species representative of both North Atlantic and North Pacific genera, of warm water origin, of cool water origin and of Arctic water origin.

There are 7 species (confirmed) of kelps found in UK waters, one of which is a recently introduced alien (Undaria pinnatifida) and one of which is a southern species the range of which is extending northward (L. ochroleuca). The most common species in kelp beds are L. digitata and L. hyperborea, the latter often out-competing the former in shallow water in the northern parts of the UK.

The species listed in the table below are the most commonly found kelps which form the foundation of the kelp biotopes found in European waters. In the Mediterranean and on the south-western Atlantic coasts of the EU, kelp plants are often found in deeper waters and growing in more mixed communities, the kelp species therefore forming a less dominant component within the coastal ecosystems.

Illustrations and descriptions of the kelp species found in UK waters

Distribution of kelps in European coastal waters

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