Distinctive Community Patterns With Exceptional Diversity of Polychaetes Around a Tectonically Active Archipelago in the Tropical Indian Ocean

Abstract

Marine soft-sediments sustain functionally important benthic assemblages that are critical for remineralization of organic matter and supply of nutrients to the water column. While these assemblages are well studied along continental margins, investigations from insular margin that surround oceanic islands are very limited. This paper examines the distribution and standing stock of macrozoobenthos at 50, 100, and 200 m depth contours surrounding the Andaman and Nicobar archipelago in the tropical Indian Ocean. The standing stock of macrozoobenthos decreased from the mesophotic reef areas (50 m depth) to the deeper strata (200 m), particularly in the case of the dominant groups, the polychaetes and crustaceans. Smaller-sized, interstitial polychaetes and crustaceans were abundant in the coarser sandy sediments at the shallower sites. The polychaetes were represented by 606 species (279 genera) in the study, of which >50% were rare species. Based on polychaete species composition, three regions were delineated in the study area -the Nicobar margin, the western margin of the Andaman (Bay of Bengal sector), and the eastern margin of the Andaman (Andaman Sea sector). The long, uninterrupted Andaman Island chain formed a geographic barrier separating the eastern and western margins, resulting in the regional distinctions in sediment nature and hydrographic characteristics, which in turn influenced species distribution. Corresponding differences were absent in the case of the Nicobar Islands, which are widely separated by transecting channels, permitting exchange of water between the Bay of Bengal and the Andaman Sea. Within the three regions, polychaete communities changed significantly in taxonomic and functional composition with increasing depth. The well oxygenated, coarse sandy sediments around mesophotic reefs (50 m) harbored predator-dominated assemblages. The 200 m sites, which were characterized by oxygen minimum conditions (<0.5 ml.l −1 ), particularly around the Andaman Island mass, were dominated by deposit feeders. This study provides the first

Taxonomic distinctness and diversity patterns of a polychaete (Annelida) community on the continental shelf of the Southern Gulf of Mexico

“…Annelid polychaetes are among the most diverse and characteristic groups of benthic macroinvertebrates [ 24 , 25 ] and one of the richest concerning species numbers [ 26 , 27 ]; it includes nearly 11,500 accepted nominal species and is often the dominant group in benthic macrofauna [ 28 ], representing up to 60% of the species and over 70% of the abundance, mainly in soft-bottom communities [ 24 , 29 ]. They are ubiquitous in soft sediments and show significant spatial distribution patterns under the influence of environmental gradients [ 30 ]. Polychaetes can be used as “indicators” of different ecological conditions [ 31 , 32 ], and they can be particularly informative in assessing the health of benthic environments.…”

Factors Affecting Burrow Architecture of the Polychaete Perinereis Aibuhitensis

“…Polychaetes are common infauna of the coastal intertidal zone and contribute to the remediation of sediment and ecological recovery in natural waters (Koo and Seo, 2017;Chouikh et al, 2020;Gopal et al, 2020;Fang et al, 2021b). Many studies have been conducted on the relationship between sediment and polychaete from several aspects, such as sediment selectivity, irrigation, burrowing, dissolved oxygen and microbial community (Papaspyrou et al, 2006;Shull et al, 2009;Crane and Merz, 2017;Fang et al, 2021a).…”

The Sediment Selectivity of Perinereis aibuhitensis Larvae: Active or Passive?

“…Polychaeta, one of the most typical taxon of benthic communities, is a common infauna of the coastal intertidal zone involved in the reworking of sediment and ecological recovery in natural waters (Heilskov and Holmer, 2001;Koo and Seo, 2017;Chouikh et al, 2020;Gopal et al, 2020). The bioturbation behaviors of polychaetes within the sediment include feeding, burrowing, and moving, which promote nutrients exchange and oxygen flux at the sediment-water surface resulting in accelerated mineralization and decomposition of the sediment's organic matter (Duport et al, 2006(Duport et al, , 2007.…”