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 cm 2 . The average nematode densities in the NB and NN parts were 69 inds/10 cm 2 and 137 inds/10 cm 2 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 discolensisThalassomonhystera 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%).

Is the meiofauna a good indicator for climate change and anthropogenic impacts?

“…In addition to the physical disturbance due to mineral deposit extraction, the reduction in habitat heterogeneity (Zeppilli et al 2014) may permanently alter the structure of benthic communities (Leduc et al 2015 and references therein). Benthic meiofauna from polymetallic nodule areas are known from the Pacific Ocean (Hessler and Jumars 1974;Snider et al 1984;Renaud-Mornant and Gourbault 1990;Bussau et al 1995;Ahnert and Schriever 2001;Radziejewska 2002;Lambshead et al 2003;Veillette et al 2007a, b;Miljutin and Miljutina 2009a, b;Miljutina et al 2010Miljutina et al , 2011Miljutina and Miljutin 2012) and Indian Ocean (Parulekar et al 1982;Ansari 2000;Ingole et al 2000Ingole et al , 2005Singh et al 2014). The techniques used for the extraction of nodules from the seafloor involve mechanical screening, bucket or scraper methods or hydraulic approaches to lift the nodules from the seafloor (Thiel 2003).…”

The state of knowledge on deep-sea nematode taxonomy: how many valid species are known down there?

“…Nevertheless, the value of this work is still enormous because of its completeness and carefulness. Many of Bussau's species were rediscovered 5,200 km from their original location (Miljutina et al 2010). The other example in this context is the set of Vitiello's papers that contain descriptions of 85 species from the upper slope of the Mediterranean (Vitiello 1969a(Vitiello , b, 1970a(Vitiello , b, c, d, 1971(Vitiello , 1975(Vitiello , 1976Vitiello and Haspeslagh 1972).…”

“…The species richness of these communities has exceeded all scientific expectations, especially the high diversity of marine nematodes. For example, from 200 to 325 nematode morphotypes were identified in samples of about 2,000 individuals from different abyssal regions (Bussau 1993;Lambshead et al 2003;Miljutina et al 2010), and 246 nematode genera were found in a total sample of 18,000 individuals from a deep-sea nodule field of the ClarionClipperton Fracture Zone (Pacific) (Radziejewska et al 2001; Dr. V.V. Galtsova, pers.…”

Diversity of Abyssal Marine Life

“…The community structure of abyssal megafauna and macrofauna in manganese nodule fi elds was found to differ not only due to the availability and quality of food but also because of the heterogeneity in physical and chemical properties of the habitat (nodules and superfi cial sediment). Studies undertaken at the local scale (1 -5 km in distance) with the manned submersible Nautile showed for the fi rst time that nodule fi elds constitute a distinct habitat for infaunal communities, and that macrofauna and meiofauna components differ in abundance depending on the presence of nodules (Miljutina et al 2009 ).…”