Description of biotope or habitat type
Sargassum muticum on shallow slightly tide-swept infralittoral mixed substrata
Habitat (physical) description
|Salinity||Full (30-35 ppt)|
|Wave exposure||Sheltered, Very sheltered, Extremely sheltered|
|Tidal streams||Moderately strong (1-3 kn)|
|Zone||Infralittoral - upper, Sublittoral fringe|
|Depth Band||0-5 m|
Download comparative physical and biological data. The comparative tables enable a rapid comparison of the species composition and principal physical characteristics between a given set of biotopes.
- Records used to define the biotope (core records)
- Other records assigned to this biotope, marked as 'certain'
- Other records assigned to this biotope, marked as 'uncertain'
- Predicted extent of the level 3 (for sublittoral rock & deep sea) or 4 (for sublittoral sediment) habitat
Mixed substrata from the sublittoral fringe to 5m below chart datum dominated by the brown seaweed Sargassum muticum. This invasive non-native brown seaweed can form a dense canopy on areas of mixed substrata (typically 0-10% bedrock on 90-100% sandy sediment). The substrate on which this S. muticum-dominated community is able to develop is highly variable, but particularly prevalent on broken rock and pebbles anchored in sandy sediment. The pebbles, cobbles and broken bedrock provide a substrate for alga such as the kelp Laminaria saccharina. During the spring, S. muticum has large quantities of epiphytic ectocarpales and may also support some epifauna e.g. the hydroid Obelia geniculata commonly found on kelp. The brown seaweed Chorda filum, which thrives well on these mixed substrata, is also commonly found with S. muticum during the summer months. In Strangford Lough, where this biotope occurs, the amphipod Dexamine spinosa has been recorded to dominate the epiphytic fauna (this is known to be commonly found in Zostera spp. beds). S. muticum is also found on hard, bedrock substrates within L. saccharina canopies. S. muticum plants on hard substrate area, under a dense L. saccharina canopy, are typically smaller and at a much lower density, especially where a lush, under-storey exists with red seaweeds such as Ceramium nodolosum, Gracilaria gracilis, Chylocladia verticillata, Pterosiphonia plumula and Polysiphonia elongata and the green seaweeds Cladophora sp., Ulva lactuca and Bryopsis plumosa. The anthozoan Anemonia viridis and the crab Necora puber can be present. More information is necessary to validate this description.
Where there is a greater proportion of bedrock or boulders (15-100%) L. saccharina will typically dominate the canopy. Areas with pebble cover on a hard substrate are colonised by S. muticum, but individuals quickly become peripatetic and are lost.
|Taxon||Relative importance of taxon for defining this community (%)||Typical abundance - SACFOR scale||% of core records where taxon was recorded|
|Cliona celata||1||21-40 %|
|Anemonia viridis||3||Rare||41-60 %|
|Necora puber||1||Occasional||21-40 %|
|Gracilaria gracilis||13||Frequent||61-80 %|
|Chylocladia verticillata||4||Occasional||41-60 %|
|Ceramium nodulosum||9||Occasional||61-80 %|
|Pterothamnion plumula||1||Occasional||21-40 %|
|Polysiphonia elongata||1||Rare||21-40 %|
|Chorda filum||2||Occasional||21-40 %|
|Laminaria saccharina||13||Frequent||61-80 %|
|Cystoseira baccata||1||Occasional||21-40 %|
|Sargassum muticum||33||Common||81-100 %|
|Ulva lactuca||3||Frequent||41-60 %|
|Bryopsis plumosa||2||Occasional||21-40 %|
Not applicable or unknown.