Marine Institute
SeaRover Dive Video

D486 Transect 28 Sloping mud with Phormosoma placenta urchins, juvenile holothurian aggregation. Features of Interest: canyon Water Depth: 1702-1583 m

Highlights: Fish Umbellula octocoral & Pyrosoma urchins Octopus

The substrate at this site is that of soft, featureless sand on a steep to very steep incline. The echinoid Echinoidea sp. 4 (from Howell & Davies 2010), is the most common species throughout; grenadier are present in low numbers. Small dense patches the elpidiid holothurian occur between 1660 m and 1630 m depth. Large burrows, one of which is occupied by a galatheid are first observed at 1630 m. At the top of the slope two species of sea pens Umbellula sp. and Kophobelemnon sp. are present.

START VIDEO [00:00:00]/12:29 [1] The whole transect was spent on muddy substrate with the urchin Phormosoma placenta dominating the epifauna (at least one every [00:10:00]). [00:13:00] [2] While the urchins and mud continue, there this area of the transect encounters multiple patches of thousands of juvenile holothurians (probably from the family Elpidiidae). These continue until [00:25:00] [3] return to P. placenta dominated mud slopes. Stops for imagery at [00:38:00]-[00:39:00] (Phormosoma), [00:59:00]-[01:01:00] (Phormosoma/Umbellula), [01:05:00]-[01:06:00] (octopus), then [01:07:00] stop to take a pushcore before END VIDEO [01:15:00]/13:44.

Progression Start Duration Code Name
1[00:00:00]00:13:38M.AtLB.Mu.UrcComUrchin dominated community on Atlantic lower bathyal mud
2[00:13:39]00:11:58M.AtUA.Mu.HolComHolothurian dominated community on Atlantic upper abyssal mud
3[00:25:38]00:50:09M.AtLB.Mu.UrcComUrchin dominated community on Atlantic lower bathyal mud

Unknown sp. ring (small)? : 1117 : R
Cnidaria
Cerianthidae sp. 1 : 2 : R
Actiniaria sp. 20 : 605 : R
Phelliactis sp. 1 : 255 : O
Acanella arbuscula : 585 : O
Umbellula sp. : 581 : O
Scyphozoa (indet.) : 1134 : R
Annelida
Aphroditidae sp. 1 : 146 : R
Arthropoda
Caridea (indet.) : 1077 : R
Colossendeis sp. 1 : 1059 : R
Mollusca

Octopoda (indet.) : 659 : R
Echinodermata
Brisingidae sp. : 274 : O
Zoroaster fulgens : 988 : O
Pseudarchaster sp. 1 : 433 : R
cf. Henricia sp. (deep) : 1154 : R
Pterasteridae sp. : 1115 : O
Hygrosoma sp. : 1125 : R
Phormosoma placenta : 555 : F
cf. Amperima sp. : 628 : R
Elpidiidae sp. : 1116 : F
Benthothuria sp. : 1124 : O
Chordata
Harriotta raleighana : 936 : R

Synaphobranchus kaupii : 440 : O
Coryphaenoides guentheri : 577 : O
Coryphaenoides rupestris : 566 : O
Trachyrincus sp. : 446 : O
Lepidion cf. guentheri : 1160 : O
Polyacanthonotus rissoanus : 552 : R
Notacanthiformes (indet.) : 1034 : R
Cataetyx laticeps : 1111 : R
Zoarcidae sp. 2 : 291 : R
Actinopterygii sp. 3 : 930 : R

Number of species = 32

© Marine Institute, MERC Consultants, Bernard Picton 2022