Description of biotope or habitat type
Polychaete/bivalve-dominated mid estuarine mud shores
Habitat (physical) description
|Salinity||Full (30-35 ppt), Reduced (18-30ppt), Variable (18-35 ppt)|
|Wave exposure||Sheltered, Very sheltered, Extremely sheltered|
|Substratum||Sandy mud, mud|
|Depth Band||Lower shore, Mid shore, Upper shore|
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'
Point data based on records in the UK Marine Recorder Snapshot.
Mid estuarine shores of fine sediment, mostly in the silt and clay fraction (particle size less than 0.063 mm in diameter), though sandy mud may contain up to 40% sand (mostly very fine and fine sand). Littoral mud typically forms extensive mudflats, though dry compacted mud can form steep and even vertical structures, particularly at the top of the shore adjacent to saltmarshes. Little oxygen penetrates these cohesive sediments, and an anoxic layer is often present within millimetres of the sediment surface. Most mid estuarine muddy shores are subject to some freshwater influence, though at some locations more or less fully marine conditions may prevail. Mid estuarine muds support rich communities characterised by polychaetes, bivalves and oligochaetes.
Principally along mid estuarine shores. The mid estuarine communities may also be present in sheltered inlets, straits and embayments which are not part of major estuarine systems, though usually there is some freshwater influence.
Enteromorpha spp. and Ulva lactuca may form mats on the surface of the mud during the summer months, particularly in areas of nutrient enrichment or where there is significant freshwater influence.
|Taxon||Relative importance of taxon for defining this community (%)||Typical abundance - SACFOR scale||Typical abundance - (count per m2)||% of core records where taxon was recorded|
|Eteone longa||3||Abundant||104||41-60 %|
|Hediste diversicolor||16||Abundant||899||81-100 %|
|Nephtys hombergii||3||Common||75||41-60 %|
|Pygospio elegans||8||Common||719||61-80 %|
|Streblospio shrubsolii||8||Common||731||61-80 %|
|Aphelochaeta marioni||2||Abundant||1794||21-40 %|
|Tharyx killariensis||2||Common||429||21-40 %|
|Manayunkia aestuarina||2||Common||883||21-40 %|
|Tubificoides benedii||14||Abundant||3690||61-80 %|
|Tubificoides pseudogaster||2||Common||2095||21-40 %|
|Hydrobia ulvae||11||Common||3031||61-80 %|
|Cerastoderma edule||2||Common||132||41-60 %|
|Macoma balthica||15||Common||591||81-100 %|
|Abra tenuis||2||Common||214||21-40 %|
|Scrobicularia plana||3||Abundant||112||41-60 %|
Not applicable or unknown.