Marine Institute
SeaRover Dive Video

D490 Transect 40 Psolus encrusted cobbled/boulders, rock ledges, track along one for half dive, some Desmophyllum cf. dianthus on overhangs and fossil burrows evident. Features: escarpment Water Depth: 835-569 m

Highlights: Stylasterid corals Large boulder Anglerfish - Lophius piscatorius Desmophyllum dianthus under overhang

This site is characterised by carbonate sediment in the form of cliffs, ledges and overhangs. The substrate of the canyon floor is that of fine soft sediment with some coarse sediment and the occasional stones or rock. On the side of the canyon the ground is carbonate with varying amounts of a fine sediment overlay; this is interspersed with cliffs which vary in height from 1 m -1.5 m to 0.5 m in height. Overhangs are also variable with some being very prominent while others are less pronounced. The terraces vary in their degree of steepness and also in the substrate; some are soft sediment which others have exposed carbonate outcrops. Occasional rocks are a present on most terraces.

The echinoid Cidaris cidaris and fish species Lepidion eques are common throughout this site. The holothurian Psolus sp. is commonly observed in the deeper areas while the variety of anemone species increases moving up the slope. Where areas of featureless sediment occur the conspicuous fauna consists of C. cidaris, occasional anemones and holothurians. On the terraces it reflects the amount of hard and/or soft substrate. In the deeper areas the fauna is dominated by Psolus sp., C. cidaris, Stylasteridae sp. and a variety of encrusting sponges. In shallower areas Psolus sp. ceases to be recorded and the variety of anemones appears to increase.

Cliff faces are colonised by Stylasteridae sp., encrusting sponges and serpulids and occasionally cerianthids are recorded here too. Burrows, in places occupied by galatheids, are present. Small clumps of the stone coral Lophelia pertusa are noted in the deeper parts of the canyon slope. On overhangs dense beds of the cup coral Desmophyllum sp. occur, among these a variety of small anemone-like fauna are noted. Tubes cf. sabellid tubes are also present. Where the overhang is very prominent the fauna is very rich and a strong current is in evidence. On the shallowest of these overhangs fishing material was observed.

START VIDEO A [00:00:00]/18:46 [1]. The dive starts on coarse mixed sediment of sand/gravel/pebbles with urchins, mainly Cidaris cidaris. [00:05:00] [2] cobbles and boulders on sand mark the bottom of the main escarpment feature, colonised by a sparse encrusting community dominated by the sedentary holothurian Psolus squamatus, C. cidaris is also abundant. The escarpment presents as sloping and sometimes vertical sedimentary rock with a heavy sand veneer, while ledges support relatively dense cobble/boulder fields. [00:23:00] [3] Steep vertical sedimentary rock and steeply inclined ledges with heavy sand veneer promote an extended area dominated by C. cidaris. [00:26:00] [4] a return to the alternating ledges of cobbles/boulders and areas of sand veneered sedimentary rock and the P. squamatus/C. cidaris mosaic. [00:28:00] [5] a more gentle upslope promotes deeper sand. Here sparse/patchy cobbles are encountered and the sand displays a sparse epifaunal community with Actiniidae sp. (OTU41) being the most obvious reoccurring species (this may be Bolocera tuediae but the column is never visible and it seems to be burrowed in the sediment). [00:44:00] ROV laterals to the right. [00:46:00] ROV heads straight forwards again. [00:55:00] [6] C. cidaris is again abundant with cobbles still hosting P. squamatus. (Note there is one boulder which displays a barnacle dominated community). This continues until the edge of a drop-off. [01:03:00]-[01:05:00] seafloor not visible due to descent over cliff. [01:05:00] The seafloor again visible showing more terraced sedimentary rock with sand veneer and ledges with cobbles and boulders as before (continued C. cidaris/P. squamatus) [01:10:00] ROV traverses right. [01:26:00]-[01:27:00] ROV ascends a little before traversing again. (Note [01:32:00] Another solitary boulder dominated by barnacles while others are P. squamatus dominated.) [01:34:55] [7] ascend and traverse vertical sedimentary rock cliff with sparse encrusting community dominated by serpulids. C. cidaris is also present. Reach lip of cliff and begin long traverse along this cliff edge. Boulders and cobbles (with P. squamatus) can be seen on the ledge above, while serpulids continue to dominate the vertical sedimentary rock. Occasional sparse occurrence of the overhang/escarpment assemblage (Desmophyllum cf. dianthus and Actiniaria sp. 13 (OTU478)) seen on other dives on this escarpment. C. cidaris can be seen both occasionally on the vertical sedimentary rock, and on the sediment veneered sedimentary rock shelf. END VIDEO A 20:40.

START VIDEO B [01:53:00]/20:41. [02:09:00] 30s of obscured vision due to sediment disturbance. [02:19:00] one of the brief areas with an overhang community. [02:27:00] [8] Stop traversing the cliff edge and ascend over the cobble/boulder field (P. squamatus/C. cidaris). [02:28:00] [9] The cobbles with P. squamatus become patchy, again proceeding over deeper sediment veneer with sparse Actiniidae sp. being the most apparent epifauna. [02:32:00] Stop to take a pushcore, then END VIDEO B [02:36:20]/21:24.

Progression Start Duration Code Name
7[00:00:00]01:53:44M.AtUB.Ro.SpaEncSparse encrusting community on Atlantic upper bathyal rock and other hard substrata
2[00:05:39]00:17:42M.AtMB.Ro.SpaEnc.PsoAnoPsolus squamatus, Anomiidae, serpulid polychaetes and Munida on Atlantic mid bathyal rock and other hard substrata
4[00:26:41]00:01:58M.AtMB.Ro.SpaEnc.PsoAnoPsolus squamatus, Anomiidae, serpulid polychaetes and Munida on Atlantic mid bathyal rock and other hard substrata
5[00:28:40]00:26:29M.AtMB.SaAtlantic mid bathyal sand
8[00:34:56]00:00:52M.AtMB.Ro.SpaEnc.PsoAnoPsolus squamatus, Anomiidae, serpulid polychaetes and Munida on Atlantic mid bathyal rock and other hard substrata
9[00:35:49]00:06:57M.AtMB.SaAtlantic mid bathyal sand

Porifera encrusting sp. 1 (white) : 1 : R
Blue Porifera encrusting : 800 : R
Cerianthidae sp. 1 : 2 : O
Pachycerianthus multiplicatus : 458 : R
Actiniaria sp. 13 (pink/purple) : 478 : R
Actiniaria sp. 20 : 605 : R
Actiniaria sp. 24 : 907 : R
Actiniidae sp. (sand Bolocera) : 41 : R
Halcampoididae sp. 1 : 23 : R
Corallimorphidae sp. 1 : 39 : R
Corallimorphidae sp. 2 : 43 : R
Caryophyllia sp. 2 : 6 : R
Desmophyllum cf. dianthus : 335 : R
Lophelia pertusa : 250 : O
Madrepora oculata : 251 : O
Zoanthidae sp. 2 : 586 : R
Anthomastus grandiflorus : 278 : R
Anthothela grandiflora : 311 : R
Hydrozoa (flat branched) : 56 : O

Corymorphidae sp. : 120 : R
Pliobothrus sp. : 207 : R
Sabellidae sp. 1 : 54 : R
Serpulidae sp. 1 : 106 : F
Chaceon affinis : 254 : O
Paromola cuvieri : 304 : O
Majidae sp. 1 : 11 : R
Munida sarsi : 200 : R
Paguridae sp. : 205 : R
Mysida (indet) : 1026 : R
Colus sp. : 113 : R
Margarites sp. 1 : 277 : R
Brachiopoda sp. 1 : 34 : R
Reteporella sp. : 204 : R
Ophiuroidea (indet.) : 1076 : R

Stichastrella rosea : 198 : R
Ceramaster/Peltaster/Plinthaster sp. 2 : 388 : R
Echinus sp. : 445 : R
Cidaris cidaris : 211 : O
Araeosoma fenestratum : 188 : R
Psolus squamatus : 252 : R
Ascidiacea sp. (clear) : 591 : R
Chimaera monstrosa : 265 : R
Synaphobranchus kaupii : 440 : O
Merlangius melangus : 1019 : R
Brosme brosme : 258 : R
Molva molva : 654 : R
Nezumia aequalis : 1003 : R
Coelorinchus caelorhincus : 303 : R
Coryphaenoides rupestris : 566 : R
Trachyrincus sp. : 446 : R
Lepidion eques : 249 : O
Lophius piscatorius : 273 : O
Helicolenus dactylopterus : 227 : R

Number of species = 53

© Marine Institute, MERC Consultants, Bernard Picton 2022