Coggan and Diesing 2012

scientific chapter |

Rock ridges in the Central English Channel

Coggan RA, Diesing M


The English Channel is a funnel-shaped, ENE–WSW-trending, shallow shelf sea between France and England. Hydrodynamically, it is a tide-dominated environment but is also influenced by long swell waves approaching from the open Atlantic Ocean. The Channel is situated at the boundary zone between Lusitanean and Boreal biogeographical provinces. The human impact on the benthic environment is assessed to be predominantly high to very high, including shipping, selective extraction (demersal fishing and aggregates), and obstruction (cables, wrecks), among others. Biological communities were compared across the three main geomorphic features, namely flat seabed, bedrock ridges and the palaeovalley, considering both the taxa recorded and the biotopes identified during the video analysis. Sixty-two taxa were identified to various levels of taxonomic precision and the analysis presented here is based on their relative frequency of occurrence. Geophysical and biological analysis revealed an extensive system of rock ridges located 30 km south of the Isle of Wight in water depths ranging between 40 and 80 m below Chart Datum. The feature extends 100 km in an east–west direction and 15 km in a north–south direction, covering ca. 1,100 km2 of seafloor. The rock habitat supports a substantial coverage of fauna including sponges, bryozoans, hydroids and anemones. Three major geomorphic feature types were identified, namely flats, rock ridges, and a palaeovalley. Surrogacy can be high for taxa that exploit niche habitats but is generally low when considering habitats and biotopes assigned according to the European Nature Information System (EUNIS) habitat classification scheme.

Depth range
40- 80 m

Mesophotic “mentions”
0 x (total of 3530 words)

* Presents original data
* Focused on 'mesophotic' depth range
* Focused on 'temperate mesophotic ecosystem'

Community structure

Actiniaria and Ceriantharia (Sea anemones)
Algae (Macro, Turf and Crustose Coralline)
Octocorallia (Soft Corals)
Other invertebrates
Porifera (Sponges)


Drop / Towed Video
Sonar / Multibeam

Author profiles