Marine Institute
SeaRover Dive Video

D649 Transect 38 Muddy steep slope with scattered dense Lophelia framework on mud and carbonate mounds. P2. Water Depth: 950m. Feature: Slope

Highlights: Pink soft coral Crinoids Octopus

Of note: Corals Desmophyllum, occasionally Madrepora and monofilament fishing line.

The bottom current is very strong and the seafloor is subject to scour, with development of wave forms throughout. Initially the substrate is pebbly, moving into ground dominated by coral rubble. Towards the top of the slope the substrate is sand. Fauna consists of clumps of live Desmophyllum and occasionally Madrepora. There are a lot of Clavulariidae octocorals and a single Acanthogorgia. The echinoid Cidaris is abundant, some anemones and hermit crabs also observed. The crinoid Koehlermetra porrecta is dense in places. Monofilament fishing line was observed towards the end of the dive.

START VIDEO [00:00:00]/20:58. Muddy steep slope with scattered dense Lophelia framework on mud and carbonate mounds. [1] The dive starts with a core sample, then aborted. Here mud, sand, pebbles and cobbles on gentle down slope. Sand ripples are covered in barnacle shells/shell hash. [00:10:00] ROV stops for imagery of Clavulariidae sp. [00:16:00] [2] Dense coral rubble of possibly Lophelia pertusa on gentle muddy/sandy upslope. [00:29:00] [3] Here dense coral framework hosting with a few epifauna species. [00:31:00] [4] Biotope changes into carbonate bedrock with colonies of L. pertusa/Madrepora oculata and Koehlermetra porrecta. [00:35:00] [5] Biotope changes again into coarse sediment with coral rubble and coral gravel. [00:50:00] Behavioural note:Trachyscorpia cristulata feeding on small eel, possibly Synaphobranchus kaupii. [00:51:00] ROV stops for imagery of T. cristulata. [00:55:00] [6] Now sediment change into rippled sand/mud with scarce and sparse epifauna. A few scattered boulders and pebbles with colonies of L. pertusa. [01:02:00] [7] Rippled sand and scattered colonies of coral rubbles. [01:03:00] ROV stops for sampling of two pushcores until END VIDEO [01:07:00]/22:04.

Progression Start Duration Code Name
1[00:00:05]00:20:12M.AtMB.MuAtlantic mid bathyal mud
2[00:20:18]00:08:02M.AtMB.Co.MixCor.DisLopDiscrete Lophelia pertusa colonies on Atlantic mid bathyal coarse sediment
3[00:28:21]00:02:56M.AtMB.Bi.CorReeAtlantic mid bathyal cold water coral reef (biogenic structure)
4[00:31:18]00:04:21M.AtMB.Ro.MixCor.DisLopDiscrete Lophelia pertusa colonies on Atlantic mid bathyal rock and other hard substrata
5[00:35:40]00:20:55M.AtMB.Co.MixCor.DisLopDiscrete Lophelia pertusa colonies on Atlantic mid bathyal coarse sediment
6[00:56:36]00:05:42M.AtMB.MuAtlantic mid bathyal mud
7[01:02:19]00:05:01M.AtMB.Co.MixCor.DisLopDiscrete Lophelia pertusa colonies on Atlantic mid bathyal coarse sediment

Cnidaria
Pachycerianthus multiplicatus : 458 : R
Actiniaria sp. 20 : 605 : R
Lophelia pertusa : 250 : A
Acanthogorgia cf. armata : 608 : R
Pseudoanthomastus sp. : 1080 : R
cf. Clavulariidae sp. : 289 : F
Pliobothrus sp. : 207 : O
Arthropoda
Munida tenuimana : 339 : R

Paguridae sp. : 205 : R
Mollusca
Graneledone sp. 1 : 937 : R
Hypsogastropoda sp. : 621 : R
Echinodermata
Koehlermetra porrecta : 315 : F
Pterasteridae sp. : 1115 : R
Cidaris cidaris : 211 : C
Hygrosoma sp. : 1125 : O
Chordata

Synaphobranchus kaupii : 440 : R
Lepidion eques : 249 : R
Trachyscorpia cristulata : 1216 : R

Number of species = 18

© Marine Institute, MERC Consultants, Bernard Picton 2022