Marine Institute
SeaRover Dive Video

D470 Transect 24 Entirely mud although depressions and gullies visible, sparse sea pens, juvenile holothurian aggregation. Features of Interest: canyon Water Depth: 2227-2192 m

Highlights: Plastic litter

The system ranges from 2215 m to 2202 m and the substrate is largely that of soft sediment. Conspicuous fauna are sparse and primarily include sea pens, cerianthids and grenadiers with some whip corals Stichopathes sp. towards the top of the feature. Numerous deep bowl shaped depressions (1-2 m deep) are evident in one area with grenadiers found at the base. One such trench-like depression ran into the canyon system. These features occur between 55° 02.22503 N 10° 38.6428 W and 55° 02.1843 N, 10° 38.6706 W.

START VIDEO [00:00:00]/22:37 [1] Transect starts on a relatively flat mud bottom with occasional burrows and many tracks. Epifauna is sparse but there are occasional encounters with Distichoptilum gracile, Umbellula sp . and other sea pens, along with caryophyllid cup corals. [00:01:00] encounter small depression (c1-2m wide/50cm deep) in the mud suggestive of a shape in the underlying rock. [00:02:00] ROV turns ~180. [00:04:00] ROV turns ~90. [00:06:00] ROV turns 90. [00:08:00] there is more of a gentle slope on the landscape down to the right, ROV diagonally traverses uphill. [00:22:00] ROV stopped on bottom for 20secs then carry on (good to gauge grain size due to sediment disturbance) [00:35:00] ROV comes off bottom, seafloor obscured. [00:36:00] seafloor re-acquired. [00:42:00] large depressions visible, interpreted as representing small canyon tributary axes, based on the multibeam/plan. The transect bisects several of these, 2-10m wide and 1-4m deep. [00:54:00] ROV stopped to inspect plastic debris (Garlic Baguettes packet with Phelliactis sp . anemone attached) in the middle of a depression. Again useful to gauge grain size here the mud is finer grained. [00:57:00] [2]: while the fauna is still sparse and similar to before, small objects start littering the seafloor. These are either juvenile holothurians or their lebensspurren (excrement in this case). The video and images are not clear enough to define this so the holothurian dominance is left as a question mark. [01:04:00] [3]: the holothurians are absent here as the slope ascends over an interfluve again. [01:05:00] [4]: descending again into a small axis, there is a dense aggregation of live juvenile holothurians forming a stripe on the seafloor (Elpidiidae sp . identification cannot be made further than this from the imagery), ascending out of the axis onto the final interfluve area, further juvenile holothurians are encountered dispersed across the landscape as seen earlier, this time with images confirming that there are live holothurians present. Sea pens become more frequent here but are still generally sparse. END VIDEO [01:23:00]/00:00.

Progression Start Duration Code Name
1[00:00:00]00:57:45M.AtLB.MuAtlantic lower bathyal mud
3[01:04:23]00:00:38M.AtLB.MuAtlantic lower bathyal mud
4[01:05:02]00:18:00M.AtUA.Mu.HolComHolothurian dominated community on Atlantic upper abyssal mud

Unknown Annelida or Foraminifera : 1073 : R
Unknown sp. ring (small)? : 1117 : R
Cnidaria
Cerianthidae sp. 1 : 2 : R
cf. Halcampoididae sp. : 984 : R
Phelliactis sp. 1 : 255 : O
Caryophyllia sp. 2 : 6 : O
Anthomastus grandiflorus : 278 : R
Acanella arbuscula : 585 : O
Pennatulacea (indet.) : 1114 : R
Distichoptilum gracile : 1108 : O
Umbellula sp. : 581 : O
Arthropoda
Caridea (indet.) : 1077 : R

Munnopsidae sp. : 1102 : R
Mollusca
Colus sp. : 113 : R
Echinodermata
Asteronyx loveni : 471 : R
Ophiomusa lymani : 551 : O
Stichastrella rosea : 198 : R
Pseudarchaster sp. 1 : 433 : R
Pterasteridae sp. : 1115 : R
Echinidae sp. (white) : 559 : R
Phormosoma placenta : 555 : R
Elpidiidae sp. : 1116 : O
Chordata
Synaphobranchus kaupii : 440 : O

Bathysaurus ferox : 1112 : R
Brosme brosme : 258 : O
Coryphaenoides guentheri : 577 : F
Halosauridae sp. : 1113 : O
Polyacanthonotus rissoanus : 552 : O
Zoarcidae sp. 1 : 259 : R
Actinopterygii sp. 3 : 930 : R

Number of species = 30

© Marine Institute, MERC Consultants, Bernard Picton 2022