Table 1. The ecological summary statistics of the nine Cobb Seamount communities identified by the present study.

		Frequency of occurrence									Importance ranking
Community		1	2	3	4	5	6	7	8	9	1	2	3	4	5	6	7	8	9
n		11	52	120	68	81	82	301	427	489	11	52	120	68	81	82	301	427	489
Ochrophyta
	Desmarestia viridis	46	0	0	0	0	0	0	0	0	7	35	37	37	35	43
Rhodophyta
	Corallinales spp.	100	100	24	0	9	0	0	0	0	12	2	45	5	8	7
Porifera
	cf Acarnus erithacus	55	8	0	0	0	0	0	0	0	8	16	26	23	21	29
	Auletta sp.	0	0	3	2	1	0	0	0	0	40	30	25	44	45	37
	Demospongiae sp.	0	37	1	2	0	0	0	0	0	32	5	22	22	15	23
	Farrea occa	0	0	0	0	0	0	0	7	1							16	11	16
	Halichondria panacea	9	58	23	4	1	0	0	0	0	38	6	17	10	6	11
	Rossellidae spp.	0	0	0	0	0	0	3	19	3							13	4	11
Cnidaria
	Actiniaria sp.	0	0	0	0	0	0	35	0	0							2	6	6
	Anthoptilum spp.	0	0	0	0	0	0	1	3	15							10	18	7
	Bathypathes sp.	0		0	0	0	0	12	2	41							12	3	2
	Corynactis californica	91	0	0	0	0	0	0	0	0	1	25	27	24	22	30
	Desmophyllum dianthus	0	2	31	6	9	0	0	2	0	22	19	6	19	39	12	26	24	22
	Gersemia sp.	0	0	0	0	0	0	0	3	0							20	15	17
	Halipteris willemoesi	0	0	0	12	0	15	0	0	0	33	22	18	9	16	10	0	0	0
	Heteropolypus ritteri	0	0	0	0	0	0	5	7	27							7	12	5
	cf Hormathiidae sp.	0	0	0	0	0	0	0	4	0							21	13	15
	Isididae spp.	0	0	0	0	0	0	1	34	9							5	2	12
	Lillipathes cf lillei	0	0	0	0	0	0	2	6	38							4	5	1
	Pennatulacea sp.	0	0	0	0	0	0	4	3	1							23	33	23
	Primnoidae spp.	0	0	0	0	0	0	0	25	1							6	1	8
	Stichopathes sp.	0	0	0	0	0	0	1	7	3							15	17	28
	Stomphia didemon	0	39	0	0	0	0	0	0	0	34	4	19	17	17	25
	Stylaster spp.	0	14	98	13	93	1	0	4	0	13	7	1	3	1	3	24	14	14
	Swiftia simplex	0	0	0	0	0	0	0	4	1							17	19	27
Annelida
	Paradexiospira sp.	9	0	32	12	1	1	0	0	0	43	14	4	43	10	17
	Phyllochaetopterus prolifica	55	0	0	0	0	0	0	0	0	6	34	34	35	32	41
	Protula pacifica	9	52	54	18	3	0	0	0	0	20	9	3	20	3	5
	Spiochaetopterus costarum	9	12	3	54	1	50	0	0	0	27	20	8	2	4	4
Arthropoda
	Chionocetes tanneri	0	0	0	0	0	0	18	3	13							9	10	26
	Chirostylidae sp.	0	0	0	0	0	0	8	40	46							3	25	10
	Chorilia longipes	28	4	1	0	1	0	0	1	1	11	24	40	30	44	34	29	34	29
	Lithodes cousei	0	0	0	0	0	0	1	2	1							34	31	32
	Pargurus kennerlyi	0	19	22	32	77	72	0	0	0	15	12	9	18	2	6
Mollusca
	Calliostoma spp.	18	0	0	0	0	0	0	0	0	2	26	28	36	23	31
	Crassadoma gigantean	55	0	0	0	0	0	0	0	0	4	32	32	33	30	39
	Fusitriton oregonensis	0	8	12	3	5	0	0	0	0	30	38	14	32	43	21
	Leptochiton rugatus	55	0	0	0	0	0	0	0	0	5	33	33	34	31	40
	Tritoniidae spp.	0	0	0	0	0	0	0	1	1							27	29	31
Brachiopoda
	Laqueus californianus	0	35	33	91	14	26	0	0	0	16	42	39	1	5	24
Bryozoa
	cf Reginella hippocrepis	27	6	0	0	0	0	0	0	0	10	15	35	36	33	42
Echinodermata
	Ampheraster sp.	0	0	0	0	0	0	3	1	2							30	28	35
	Apostichopus leukothele	0	14	23	12	9	1	0	0	0	21	44	10	42	34	15
	Asteronyx loveni	0	0	0	6	0	45	0	0	0	26	17	11	29	9	2
	Brisingidae sp.	0	0	0	0	0	0	0	0	8							14	21	9
	Ceramaster patagon	0	0	4	2	0	0	0	0	0	41	31	16	45	29	38
	Florometra serratissima	27	64	0	2	1	1	1	4	0	17	1	12	13	13	19	28	20	18
	Henricia sanguine	0	6	6	2	1	0	0	0	0	37	23	24	39	37	27
	Hippasteria phrygiana	0	0	0	2	0	0	1	2	0	45	41	41	14	42	45	33	26	19
	Mesocentrotus franciscanus	64	0	0	0	0	0	0	0	0	3	28	31	31	27	35
	Ophiopholis bakeri a	0	10	37	0	0	0	0	0	0	23	39	2	7	7	13
	Ophiura sarsii	0	0	2	2	21	94	0	0	0	18	11	7	6	40	1
	Pannychia cf moseleyi	0	0	0	0	0	0	33	50	43							11	23	34
	Pseudarchaster sp.	0	0	0	0	0	0	1	6	0							19	8	13
	Psolus squamatus	0	0	0	0	0	0	4	3	27							8	7	4
	Pteraster sp.	0	0	0	0	0	0	0	1	1							31	32	33
	Rathbunaster californicus	0	2	8	2	1	7	0	2	0	35	229	823	227	120	36	25	22	21
	Stronglocentrotus pallidus	0	0	6	0	1	0	0	0	0	39	27	13	28	41	33
	Thrissacanth sp.	0	0	0	0	0	0	0	3	0							22	16	20
Chordata
	Antimora microlpis	0	0	0	0	0	0	0	1	0							35	30	30
	Ascidiacea sp. 1 (cream)	27	10	30	0	4	0	0	0	0	19	40	5	8	14	14
	Ascidiacea sp. 2 (white)	18	8	3	0	1	0	0	0	0	14	18	42	21	38	28
	cf Coryphaenoides acrolepis	0	0	0	0	0	0	7	4	3							18	35	24
	Cottidae sp.	0	12	8	3	6	26	0	0	0	24	43	38	15	25	9
	Embassichthys bathybius	0	0	0	0	0	0	1	2	0							32	27	25
	Sebastes aleutianusb	0	2	3	15	1	0	0	0	0	36	37	43	4	26	26
	Sebastes alutus	0	0	3	2	0	0	0	0	0	42	36	21	41	36	44
	Sebastes emphaeus	0	27	14	15	1	0	0	0	0	25	10	30	25	11	16
	Sebastes helvomaculatus	18	39	26	18	28	0	0	0	0	44	13	36	38	19	8
	Sebastes rosaceus	36	2	2	2	0	0	0	0	0	9	45	44	40	24	32
	Sebastes variegatus	0	0	10	12	3	0	0	0	0	31	21	20	11	28	22
	Sebastes wilsoni	0	50	4	2	0	0	0	0	0	28	3	29	16	12	18
	Sebastes zacentrus	0	23	13	0	3	0	0	0	0	29	8	15	12	18	20
	Sebatolobus alascanus	0	0	0	0	0	0	85	19	7							1	9	3

For each community, the frequency of occurrence of benthic megafauna was calculated as the percentage of images in which the taxon was present (0% = absent, 100% = always present). The rank order of taxa importance for a community was assigned by the cluster analyses (1 = most important, no ranking = not included in the clustering process). The clustering of communities 1 to 6 and 7 to 9 considered 45 and 35 taxa respectively (which are therefore the lowest possible ranking values for those communities).

^a O. bakeri was sparsely observed and inconsistently resolvable in AUV images but was observed in easily dense, resolvable patches in the ROV images. O. bakeri was therefore included in the ROV dataset but excluded from the AUV dataset.

^b S. aleutianus and S. melanostictus are indistinguishable from images and these two species are recorded as one taxon.