Description of biotope or habitat type
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Halichondria bowerbanki, Eudendrium arbuscula and Eucratea loricata on reduced salinity tide-swept circalittoral mixed substrata
Physical habitat description
| Salinity | Reduced (18-30ppt), Variable (18-35 ppt), Low (<18ppt) |
|---|---|
| Wave exposure | Sheltered, Very sheltered |
| Tidal streams | Strong (3-6 kn), Moderately strong (1-3 kn), Weak (>1 kn) |
| Substratum | Bedrock, boulders, cobbles, pebbles |
| Zone | Circalittoral |
| Depth Band | 0-5 m, 5-10 m, 10-20 m |
| Other Features |
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
Point data based on records in the UK Marine Recorder Snapshot. Predicted habitat extent is from UKSeaMap.
Description
This biotope typically occurs on circalittoral mixed substrata (bedrock, boulders, cobbles, pebbles and gravel) in the moderately strong, tide-swept narrows near the entrance of Loch Etive, although not in the extremely tide-swept Falls of Lora. This sea loch is unique in having a substantial freshwater input from the surrounding moorland, yielding the most brackish, large sea loch in Scotland. Large growths of the brackish-tolerant sponge Halichondria bowerbanki cover the cobble and boulder seabed, interspersed with Amphilectus ovulum, the hydroid Eudendrium arbuscula and the bryozoan Alcyonidium diaphanum which are particularly characteristic of these conditions. Tufts of the bryozoan Eucratea loricata are occasional in most areas. Other species recorded include Carcinus maenas, Asterias rubens, Crossaster papposus, Buccinum undatum, Pagurus berhardus, Henricia spp., Onchidoris bilamellata and Palio dubia, tolerant of the low salinity, are found in the circalittoral throughout this area. Ascidians such as Ascidiella scabra and Corella parallelogramma may also be present. A very impoverished low salinity version is present in the upper basin of Loch Etive. The biotope CuSpH is similar in several respects to this biotope and will develop in less brackish situations where species-richness is generally greater.
Situation
No situation data available.
Temporal variation
Not known.
Characterising species
| Taxon | Relative importance of taxon for defining this community (%) | Typical abundance - SACFOR scale | % of core records where taxon was recorded |
|---|---|---|---|
| Halichondria bowerbanki | 16 | Occasional | 81-100% |
| Eucratea loricata | 15 | Frequent | 81-100% |
| Balanus crenatus | 12 | Frequent | 61-80% |
| Ascidiella scabra | 11 | Common | 61-80% |
| Corella parallelogramma | 9 | Occasional | 61-80% |
| Eudendrium arbuscula | 7 | Frequent | 81-100% |
| Alcyonidium diaphanum | 3 | Occasional | 41-60% |
| Asterias rubens | 3 | Occasional | 41-60% |
| Buccinum undatum | 3 | Occasional | 41-60% |
| Pagurus bernhardus | 3 | Frequent | 41-60% |
| Amphilectus ovulum | 2 | Occasional | 41-60% |
| Carcinus maenas | 1 | Occasional | 41-60% |
| Crossaster papposus | 1 | Rare | 41-60% |
| Henricia | 1 | Occasional | 21-40% |
| Onchidoris bilamellata | 1 | Frequent | 21-40% |
| Palio dubia | 1 | Occasional | 21-40% |
Similar biotopes or habitat types
CR.MCR.CFaVS.CuSpH.VS
This sub-biotope occurs in very sheltered variable salinity bedrock, subject to moderately strong tidal streams. It is much more impoverished than CR.MCR.CFaVS.HbowEud, lacking the hydroid Eudendrium spp. Also lacks many red algae species.
CR.MCR.CFaVS.CuSpH.As
This sub-biotope occurs in more marine conditions in the outer parts of estuaries. A diverse range of cushion sponges and hydroids are present, unlike CR.MCR.CFaVS.HbowEud.Classification history of this biotope or habitat type
| Classification version | Code |
|---|---|
| 2015 (15.03) | CR.MCR.CFaVS.HbowEud |
| 1997 (97.06) | CR.ECR.BS.HBowEud |