Deep-sea nematode assemblages of the Clarion-Clipperton Nodule Province (Tropical North-Eastern Pacific)

Abstract

The deep-sea nematode assemblages of the French mining claim area in the Clarion-Clipperton Nodule Province (the Northeastern Pacific Basin, 14°N, 130°W, depth 4,947–5,046 m) were studied at species, genus and family levels. Material was obtained using multicorers and box corers. In total, 2,174 individuals from 14 stations and 21 samples were examined. The nematode assemblages from the nodule-bearing (NB) part of the sampling area differed significantly from those at the nodule-free (NN) section. The average nematode density was 103 inds/10 cm2. The average nematode densities in the NB and NN parts were 69 inds/10 cm2 and 137 inds/10 cm2 respectively. Altogether, at least 325 putative species, 97 valid genera and 33 valid families were found. The real number of nematode species for the sampling area was estimated at about 510. The richest genera were Acantholaimus (33 putative species) and Thalassomonhystera (23 putative species). The proportions of juveniles, males and females among nematode individuals were about 44%, 23% and 33% respectively. About 2/3 of all nematodes were deposit-feeders and around 1/3 were epistrate-feeders. The nematode assemblage of the studied area may be considered to be a Theristus discolensis–Thalassomonhystera sp.3 assemblage with variation of the dominant species. The dominant species at the NN site were Theristus discolensis (12.2%) and Thalassomonhystera sp. 3 (5.3%). In contrast, at the NB site, Thalassomonhystera sp. 3 was most abundant (14.1%), followed by T. discolensis (6.2%). At genus level, Thalassomonhystera (17.9%), Theristus (13.0%) and Acantholaimus (12.8%) dominated at the NN site, whereas the abundance of Theristus was half of that (6.4%) at the NB site. The most dominant families at the NN and NB sites were Xyalidae (28.1% and 16.6%, respectively), Monhysteridae (17.9% and 25.3%) and Chromadoridae (16.2% and 22.5%).