Community structure and feeding preference of nematodes associated with methane seepage at the Darwin mud volcano (Gulf of Cádiz)

Abstract

We sampled the Darwin mud volcano (MV) for meiofaunal community and trophic structure in relation to pore-water geochemistry along a 10 m transect from a seep site on the rim of the crater towards the MV slope. Pore-water profiles indicated considerable variation in upward methane (CH 4 ) flow among sediment cores taken along the transect, with highest flux in the seep sediment core, gradually decreasing along the transect, to no CH 4 flux in the core taken at a 5 m distance. Low sulphate concentrations and high levels of total alkalinity and sulphide (H 2 S) suggested that anaerobic oxidation of methane (AOM) occurred close to the sediment surface in the seep sediment core. High H 2 S levels had a genus-and species-specific impact on meiofaunal densities. Nematode genus composition varied gradually between sediment cores, with the genus Sabatieria dominating almost all sediment cores. However, genus diversity increased with increasing distance from the seep site. These limited data suggest that the community structure of seep meiofauna is highly dependent on local (a)biotic habitat characteristics, and a typical seep meiofaunal community cannot be delineated. Stable isotope values suggested the nematode diet up to 10 m from the seep site included thiotrophic carbon. The thicker hemipelagic sediment layer (photosynthetic carbon), the increased trophic diversity, and the heavier nematode δ 13 C farther from the seep site suggest a decrease in thiotrophy and an increase in photosynthetic carbon in the nematode diet. KEY WORDS: Cold seep · Diversity · Stable isotope · Nematode · Diet Resale or republication not permitted without written consent of the publisherMar Ecol Prog Ser 438: [71][72][73][74][75][76][77][78][79][80][81][82][83] 2011 There is no consistent meiofaunal response to seep conditions. Meiofaunal densities at different deepsea seeps are higher (Olu et al. 1997, Van Gaever et al. 2006 or similar (Shirayama & Ohta 1990) compared to non-seep sediments. In seep environments, nematodes usually are the predominant metazoans, although sometimes copepods dominate (Van Gaever et al. 2006). Generally, deep-sea nematodes are characterized by high local diversity (Lambshead & Boucher 2003). Cold seeps, however, exhibit substantially reduced species diversity, harbouring only a few dominant species (Levin 2005, Vanreusel et al. 2010. The low diversity in these habitats has been attributed to the harsh abiotic conditions, created by the high H 2 S and low oxygen levels (Levin 2005).Besides high biogeochemical and physical heterogeneity, seeps differ from most deep-sea environments in the local production of organic matter through chemosynthesis. Consequently, possible food sources for seep fauna, including meiobenthos are: (1) organic matter derived from symbiotic chemoautotrophic bacteria and (2) free-living chemoautotrophic bacteria, in addition to (3) the photosynthetic organic matter delivered to all deep-sea habitats. Studies on the diet of seep meiofauna are few. Both Van Gaever et al. (2006...

Trophodynamics of estuarine intertidal harpacticoid copepods based on stable isotope composition and fatty acid profiles

“…These few published results on harpacticoid copepods are in accordance with similar records on particular nematode species from the deep sea (e.g. Van Gaever et al 2006, Pape et al 2011) and coastal habitats (e.g. Bouillon et al 2008, Vafeiadou et al 2014, confirming that chemoautotrophic carbon may be an important energy source for several meiofaunal taxa.…”

Resource utilization and trophic position of nematodes and harpacticoid copepods in and adjacent to <i>Zostera noltii</i> beds

“…Terschellingia is a microvore with a very small buccal cavity, enabling ingestion of only bacteria-sized particles, and tends to be very abundant in hypoxic/anoxic sediments (Steyaert et al, 2007), where chemosynthetic processes can be important. The nematode genera Terschellingia and Sabatieria have been suggested to feed on sulfideoxidizing bacteria in deep-sea sediments too (Pape et al, 2011;Guilini et al, 2012). Sabatieria sp.…”

Meiobenthos and nematode assemblages from different deep-sea habitats of the Strait of Sicily (Central Mediterranean Sea)

“…The pockmark meiobenthic density was also reported as being much lower than in adjacent sediments in the western Mediterranean Sea (Zeppilli et al, 2012). In fact, the meiofauna from reduced sediments colonized by chemosymbiotic macrofauna often shows significantly higher standing stocks when compared with the adjacent non-seep sediment (Shirayama and Ohta, 1990;Olu et al, 1997;Pape et al, 2011;Lampadariou et al, 2013); sometimes its density does not significantly exceed the density of meiofauna from surrounding sediments (Olu et al, 1997;Pape et al, 2011). Unfortunately, it was not possible to compare the total meiobenthic density in PS with the density from the adjacent sediment.…”

“…The genus Astomonema was predominating in the North Sea pockmark followed by Leptolaimus (Dando et al, 1991). The genus Sabatieria strongly dominated in the reduced sediments of several deep-sea cold seeps in the Mediterranean (De Groote and Vanreusel, 2011;Pape et al, 2011;Lampadariou et al, 2013). Halomonhystera were noted as a strong dominant in several studies on cold seeps from polar regions; other dominants from these regions included Terschellingia, Sabatieria, Tricoma and Laimella (Van Gaever et al, 2006;Portnova et al, 2010b;Hauquier et al, 2011; for review see Vanreusel et al, 2010a).…”

“…Shirayama and Ohta, 1990;Raes and Vanreusel, 2005;Vanreusel et al, 2009;Bongiorni et al, 2010;Pape et al, 2011;Lampadariou et al, 2013). Previous studies on nematode assemblages from cold seeps revealed high variability in their density, taxonomic composition, and assemblage structures, as a function of the geographic region, depth, macrobenthic communities, remoteness from the centre of seepages (Shirayama and Ohta, 1990;Olu et al, 1997;Van Gaever et al, 2006Portnova et al, 2010a, b;Vanreusel et al, 2010a, b;Zeppilli et al, 2011).…”