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

[摘要] We studied patterns of nematode distribution alongthe western Indian continental margin to determine the influence of habitatheterogeneity and low oxygen levels on the community's taxonomic andfunctional structure. A single transect, perpendicular to the coast at14° N latitude was sampled from 34 to 2546 m depth for biologicaland environmental variables during August 2007. The oxygen minimum zoneextended from 102 to 1001 m. Nematodes (described and undescribed) wereidentified to species and classified according to biological and functionaltraits. A total of 110 nematode species belonging to 24 families were foundalong the transect. Three depth zones were identified: the shelf (depthrange: 34–102 m; highest nematode mean density:176.6 ± 37 ind 10 cm⁻²), the slope (525–1524 m;124.3 ± 16 ind 10 cm⁻²), and the basin (2001–2546 m;62.9 ± 2 ind 10 cm⁻²). Across the entire study area, thedominant species were Terschellingia longicaudata,Desmodora sp. 1, Sphaerolaimus gracilis, andTheristus 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 Terschellingialongicaudata (4.73 %) and Desmodora sp. 1 (4.42 %) weredominant 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 reflectionof the information in species abundance. Ecological information captured byadult length, adult shape, and life-history strategy was less site-specificand thus differed notably from information contained in other taxonomicgroups. The functional composition of nematodes was strongly linked to theorganic-carbon and dissolved-oxygen concentration. Seven species were foundexclusively in the oxygen minimum zone: Pselionema sp. 1,Choanolaimus sp. 2, Halichoanolaimus sp. 1, Cobbiadentata, Daptonema sp. 1, Trissonchulus sp. 1, andMinolaimus sp. 1. Correlation with a number of environmentalvariables indicated that food quantity (measured as the organic-carboncontent and chlorophyll content) and oxygen level were the major factors thatinfluenced nematode community structure and function.

[学科分类] 地球化学与岩石