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Biogeosciences An interactive open-access journal of the European Geosciences Union
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Volume 13, issue 1 | Copyright

Special issue: Low oxygen environments in marine, fresh and estuarine...

Biogeosciences, 13, 191-209, 2016
https://doi.org/10.5194/bg-13-191-2016
© Author(s) 2016. This work is distributed under
the Creative Commons Attribution 3.0 License.

Research article 15 Jan 2016

Research article | 15 Jan 2016

Structure and function of nematode communities across the Indian western continental margin and its oxygen minimum zone

R. Singh1 and B. S. Ingole2 R. Singh and B. S. Ingole
  • 1Senckenberg am Meer, DZMB, Südstrand 44, 26382 Wilhelmshaven, Germany
  • 2Biological Oceanography Division, National Institute of Oceanography, Goa, 403004, India

Abstract. We studied patterns of nematode distribution along the western Indian continental margin to determine the influence of habitat heterogeneity and low oxygen levels on the community's taxonomic and functional structure. A single transect, perpendicular to the coast at 14°N latitude was sampled from 34 to 2546m depth for biological and environmental variables during August 2007. The oxygen minimum zone extended from 102 to 1001m. Nematodes (described and undescribed) were identified to species and classified according to biological and functional traits. A total of 110 nematode species belonging to 24 families were found along the transect. Three depth zones were identified: the shelf (depth range: 34–102m; highest nematode mean density: 176.6±37ind10cm−2), the slope (525–1524m; 124.3±16ind10cm−2), and the basin (2001–2546m; 62.9±2ind10cm−2). Across the entire study area, the dominant species were Terschellingia longicaudata, Desmodora sp. 1, Sphaerolaimus gracilis, and Theristus ensifer; their maximum density was at shelf stations. Nematode communities in different zones differed in species composition. Chromadorita sp. 2 (2.78%) and Sphaerolaimus gracilis (2.21%) were dominant on the shelf, whereas Terschellingia longicaudata (4.73%) and Desmodora sp. 1 (4.42%) were dominant on the slope, but in the basin, Halalaimus sp. 1(1.11%) and Acantholaimus elegans (1.11%) were dominant. The information in a particular functional group was not a simple reflection of the information in species abundance. Ecological information captured by adult length, adult shape, and life-history strategy was less site-specific and thus differed notably from information contained in other taxonomic groups. The functional composition of nematodes was strongly linked to the organic-carbon and dissolved-oxygen concentration. Seven species were found exclusively in the oxygen minimum zone: Pselionema sp. 1, Choanolaimus sp. 2, Halichoanolaimus sp. 1, Cobbia dentata, Daptonema sp. 1, Trissonchulus sp. 1, and Minolaimus sp. 1. Correlation with a number of environmental variables indicated that food quantity (measured as the organic-carbon content and chlorophyll content) and oxygen level were the major factors that influenced nematode community structure and function.

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Several transitional settings in the western Indian continental margin, including the shelf, slope, and basin, provide multiple oxygen and other environmental gradients. These settings allowed us to investigate how oxygen and environmental factors affect and modulate the structure and function of nematode communities at the species level. An study from the Indian western continental margin with reference to nematode tolerance in the oxygen minimum zone is therefore important.
Several transitional settings in the western Indian continental margin, including the shelf,...
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