Marine Institute
SeaRover Dive Video

D465 Transect 39 Mostly mud with urchins/holothurians, areas of sloping carbonate with stalked crinoids and chrysogorgiids. Features of Interest: canyon, escarpments Water Depth: 2473-2227 m

Highlights: Stalked crinoids

Marine snow carried on a fast down slope current making visibility poor at times. From the canyon floor up to 2460 m the substrate is featureless carbonate rock with a thin overlay of sediment. A 10 m high carbonate cliff appeared at 2443 m with the only conspicuous fauna being stalked crinoids. Above this cliff the canyon slope is terraced with steep sediment inclines interspersed with carbonate cliffs. The common fauna on the canyon floor and up to 2400 m are holothurians and the small echinoid, cf. Echinus sp. On the chalk carbonate substrate stalked crinoids are the most prevalent fauna. In the terrace sediment there are burrows, at least some of which are occupied by galatheids. At the top of the canyon black coral is prevalent. Fish are not common here with only occasional grenadier recorded. Large aggregations of small elpidiid holothurians are evident between 2460 m - 2455 m.

START VIDEO [00:00:00]/11:58 [1] Muddy sediment with flocculent matter and small white echinoids (Echinidae sp. , OTU559), marine snow is falling. Patchy aggregations of juvenile holothurians are encountered mosaicked with echinoids. [00:01:00] ROV off bottom and moving right. [00:03:00] moving forwards. [00:09:00]-[00:21:00] stopped for pushcore sampling, although the mud appears to be only ~10cm deep before the ROV lifts (one failed attempt, one successful but not very full). [00:28:00]-[00:29:00] out of focus while trying to zoom on juvenile holothurians. [00:34:00]-[00:38:00] stopped. [00:41:00] mud becomes rippled. [00:47:00] [2] fauna is sparse but several Distichoptilum gracile are encountered. Some patchy areas of cobbles/mud veneered carbonate are also present but not colonised or of large enough area to qualify as a separate biotope. [00:53:00] [3] mud with cobbles/boulders before sloping/vertical carbonate are colonised mainly by stalked crinoids (especially cf. Porphyrocrinus thalassae OTU1045) and purple cf. Laetmogone sp . holothurians are also found on sloping carbonate with mud veneer. [00:59:00] [4] white echinoids (OTU559) and Ophiomusa lymanion mud with pebbles. [01:00:00] [5] another area of sloping mud/flocculent matter veneered carbonate with cf. P. thalassae and cf. Laetmogone sp. [01:02:00] [6] again mud with scattered pebbles, white echinoids and O. lymani. [01:08:00] [7] Holothurians (cf Amperima sp. , OTU628) become abundant, co-occuring with O. lymani. [01:09:00] flocculent matter no longer abundant. [01:10:00] no more pebbles. [01:15:00] [8] an area of pebbles/cobbles hosts mainly O. lymani before transitioning to [01:16:00] [9] mud with rare pebbles/cobbles and sediment dwelling Democrinus sp . (OTU1103) stalked crinoid become abundant. [01:21:00] cobbles/pebbles more consistently present on mud becoming [01:22:00] a small cobble/boulder field then [01:23:00] [10] boulders and carbonate with mud surround or veneer, Democrinus sp . still abundant where there is mud, along with Bathycrinidae sp. and cf. Porphyrocrinus thalassae attached to the hard substrate. Some Chrysogorgiidae sp . also present. [01:28:00] [11] the mud deepens and the Democrinus sp . continues with Acanella arbuscula abundant until the END VIDEO [01:44:00]/13:42

Progression Start Duration Code Name
1[00:00:00]00:47:38M.AtUA.Mu.UrcComUrchin dominated community on Atlantic upper abyssal mud
2[00:47:39]00:05:44M.AtMB.Mu.SpnMegSea pens and burrowing megafauna on Atlantic mid bathyal mud
3[00:53:24]00:05:54M.AtUA.RoAtlantic upper abyssal rock and other hard substrata
4[00:59:19]00:01:31M.AtUA.Mu.UrcComUrchin dominated community on Atlantic upper abyssal mud
5[01:00:51]00:01:08M.AtUA.RoAtlantic upper abyssal rock and other hard substrata
6[01:02:00]00:06:32M.AtUA.Mu.UrcComUrchin dominated community on Atlantic upper abyssal mud
7[01:08:33]00:06:41M.AtMA.Mu.HolComHolothurian dominated community on Atlantic mid abyssal mud
8[01:15:15]00:01:10M.AtLB.Mx.SurOphSurface dwelling ophiuroid community on Atlantic lower bathyal mixed sediment
9[01:16:26]00:07:26M.AtMB.Mu.CriComCrinoid dominated community on Atlantic mid bathyal mud
10[01:23:53]00:04:39M.AtUA.RoAtlantic upper abyssal rock and other hard substrata
11[01:28:33]00:15:45M.AtMB.Mu.CriComCrinoid dominated community on Atlantic mid bathyal mud

Cerianthidae sp. 1 : 2 : R
Actiniaria sp. 20 : 605 : R
Actinernus michaelsarsi : 554 : R
Scleractinia sp. (mud butterfly) : 1130 : R
Caryophyllia sp. 2 : 6 : R
Caryophyllia sp. 5 (bullseye) : 584 : R
Anthomastus grandiflorus : 278 : R
Chrysogorgidae sp. 1 : 1008 : O
Acanella arbuscula : 585 : O
Anthoptilum grandiflorum : 594 : R
Distichoptilum gracile : 1108 : O
Galacantha sp. : 1144 : R
Colossendeis sp. 1 : 1059 : R

Eucarida sp. : 1106 : R
Bathycrinidae sp. 2 cf. Porphyrocrinus thalassae : 1045 : O
Democrinus sp. : 1103 : F
Crinoidea sp. 1 : 131 : O
Ophiomusa lymani : 551 : R
Brisingidae sp. : 274 : O
Pseudarchaster sp. 1 : 433 : R
cf. Henricia sp. (deep) : 1154 : R
Hippasteria phrygiana : 542 : R
Hymenaster cf. pellucidus : 1110 : O
Asteroidea sp. (pink deep sediment) : 1171 : R
Echinidae sp. (white) : 559 : O
cf. Amperima sp. : 628 : O
Elpidiidae sp. : 1116 : O

Peniagone sp. : 1167 : R
Benthogone sp. : 432 : O
Mesothuria intestinalis : 536 : R
Coryphaenoides guentheri : 577 : O
Coryphaenoides rupestris : 566 : R
Lepidion cf. guentheri : 1160 : O
Halosauridae sp. : 1113 : R
Zoarcidae sp. 2 : 291 : R

Number of species = 35

© Marine Institute, MERC Consultants, Bernard Picton 2022