Megafaunal Community Structure of Andaman Seamounts Including the Back-Arc Basin – A Quantitative Exploration from the Indian Ocean

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

Temporal variation in macroinvertebrates associated with intertidal sponge <i>Ircinia fusca </i>(Carter 1880) from Ratnagiri, West coast, India.

927-932Temporal variation of macrofauna associated with a marine sponge, Ircinia fusca was studied from a tropical rocky shore along the West coast of India. Triplicate sponge samples (~100 g) were collected from January to December 2010 from Bhagwati Bandar area, Ratnagiri. A total of 22 macrofaunal taxa were found to be associated with the sponge. The community was dominated (≥80%) by the juvenile ophiuroid, Ophiactis savignyi. Syllis sp., Sipuncula and Bivalvia were the other dominant taxa. Presence of O. savignyi juveniles during most of the time in the year indicates a major recruitment in March and minor recruitment during rest of the year. Present study suggest that the O. savignyi utilize the surface area of sponge as a perfect settling and recruiting ground. It infers that the sponge Ircinia fusca is used as a breeding ground by the brittle star, Ophiactis savignyi. </span

Macrobenthic community structure of coastal Arabian Sea during the Fall intermonsoon

2223-2232<span style="font-size:9.0pt;font-family: " times="" new="" roman","serif";mso-fareast-font-family:"times="" roman";mso-ansi-language:="" en-gb;mso-fareast-language:en-us;mso-bidi-language:hi"="" lang="EN-GB">In the Arabian Sea, organic matter produced during the upwelling period reaches the seafloor by the end of the monsoon and during the fall intermonsoon period (FIM). Studies on the benthic community is lacking during this period. Therefore, we predict that the FIM period is critical in structuring the coastal benthic community. Results indicated Coscinodiscus sp. and Thalassiosira sp. were dominant in the phytoplankton and the microphytobenthos community. Zooplankton was dominated by small sized calanoid copepods followed by larval forms of polychaete and fish. Macrofauna was dominated by the juveniles of interface feeding polychaete, Paraprionospio pinnata. The quality of food from the surface flux supported the macrofaunal community and explained the successful recruitment of dominant P. pinnata.  Therefore, species composition and dominance of juveniles among the macrofaunal community suggest that macrobenthic recruitment coincides with the timing of organic matter flux so that the benthic community benefits from the sinking detritus.</span