Sautya S et al. (2011), Megafaunal community structure of Andaman seamo...

ECB-ART-50157

PLoS One 2011 Jan 31;61:e16162. doi: 10.1371/journal.pone.0016162.

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Megafaunal community structure of Andaman seamounts including the Back-arc Basin--a quantitative exploration from the Indian Ocean.

Sautya S , Ingole B , Ray D , Stöhr S , Samudrala K , Raju KA , Mudholkar A .

Abstract
Species rich benthic communities have been reported from some seamounts, predominantly from the Atlantic and Pacific Oceans, but the fauna and habitats on Indian Ocean seamounts are still poorly known. This study focuses on two seamounts, a submarine volcano (cratered seamount--CSM) and a non-volcano (SM2) in the Andaman Back-arc Basin (ABB), and the basin itself. The main purpose was to explore and generate regional biodiversity data from summit and flank (upper slope) of the Andaman seamounts for comparison with other seamounts worldwide. We also investigated how substratum types affect the megafaunal community structure along the ABB. Underwater video recordings from TeleVision guided Gripper (TVG) lowerings were used to describe the benthic community structure along the ABB and both seamounts. We found 13 varieties of substratum in the study area. The CSM has hard substratum, such as boulders and cobbles, whereas the SM2 was dominated by cobbles and fine sediment. The highest abundance of megabenthic communities was recorded on the flank of the CSM. Species richness and diversity were higher at the flank of the CSM than other are of ABB. Non-metric multi-dimensional scaling (nMDS) analysis of substratum types showed 50% similarity between the flanks of both seamounts, because both sites have a component of cobbles mixed with fine sediments in their substratum. Further, nMDS of faunal abundance revealed two groups, each restricted to one of the seamounts, suggesting faunal distinctness between them. The sessile fauna corals and poriferans showed a significant positive relation with cobbles and fine sediments substratum, while the mobile categories echinoderms and arthropods showed a significant positive relation with fine sediments only.

PubMed ID: 21297959
PMC ID: PMC3031525
Article link: PLoS One

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References [+] :

Clark, The ecology of seamounts: structure, function, and human impacts. 2010, Pubmed

	Figure 1. Bathymetric map of the Andaman Back-arc Basin including Andaman Back-arc Spreading Centre (ABSC) and locations of the underwater video transects (TVG).All the transects were located in the Back-arc Basin region only. The TVG-9 and TVG-10 were located on the cratered seamount (CSM) off Nicobar Island, TVG-11 and TVG-12 were located on the back-arc spreading ridge segments, while TVG-13 and TVG-14 were located on the rift valley of the basin floor and on the off-axial highs of the back-arc basin.
	Figure 2. Composition of substratum types of two seamounts and surrounding sea floor in the Andaman Back-arc basin, with transect codes.Please see Table 2 for details of substratum types.
	Figure 3. Megafaunal abundance along depth for two seamounts and the surrounding deep sea in the Andaman Back-arc basin.
	Figure 4. Megafaunal group composition along the CSM and SM2 seamounts and basin area in the Andaman Sea Back-arc Basin.
	Figure 5. Structure of the CSM seamount (3D model midified from Kattoju et al. 2010) with accurate locations of the TVG-10 at summit and TVG-9 at flank, and the fauna associated with it.Megabenthic communities observed on a crater seamount in the Andaman Sea. a: Holothurid; b: Euplectella sp.; c: Gorgonian; d: Squat lobster - Galatheidae; e: Demospongiae attached to a big rock, onboard sample; f: the squat lobster-Liogalathea laevirostris; g: brittle star- Ophiophyllum sp; h: dense population of megafaunal communities (gorgonians, sponges, sea urchins, brittle stars, galatheids) lived on the big boulders and uplifted slabs; i: dense patches of corals (gorgonians); j: Ophiuroidea laid on the cobbles substratum.
	Figure 6. The SM2 seamount with locations of TVG-12 at summit and TVG-11 at flank, and its associated fauna.a:The bird-nest sponge Pheronema sp; b: Munida sp; c: Pycnogonid; d: Arrow indicating the underwater photograph of bird-nest sponge; e: Black coral attached to the hard substratum.
	Figure 7. Occurrences of motility catagories on both seamounts and the basin area.
	Figure 8. nMDS analysis of substratum types along the study sites in the Andaman Sea, the seamounts CSM and SM2, and the off axis basin.
	Figure 9. nMDS analysis of megafaunal community along the study sites in the Andaman Sea, the seamounts CSM and SM2, and the off axis basin.
	Figure 10. Transect-wise distribution of megafaunal community structure indices (S: number of species, d: Margalef's index, J': evenness, H': Shannon diversity).
	Figure 11. Number of taxa reported from the Indian Ocean seamounts including the present study.A: Bezrukov, B: Equator (Indian), C: Fred, D: Lena, E: Mount Error Guyot, F: Ob' Seamount, G:Shcherbakov, H: Travin Bank, I: Unnamed Seamounts – 1234, J: Walters Shoal, K: CSM - ABB, L: SM2- ABB.
	Figure 12. Comparison of sponges recorded from seamounts around the globe.
	Figure 13. Map of Pheronema sp. distribution on the world ocean seamounts.The white circle indicates the new addition of Pheronema sp. from the seamounts in the Indian Ocean.