Meiofauna and nematodes in cold seep surface sediments collected during Maria S. Merian cruise MSM13 to the Eastern Mediterranean area

In this study the importance of spatial scales on nematode species distribution and patterns of biodiversity and turnover in cold seeps was investigated. Therefore it was identified how nematode assemblages differ in densities and composition at different spatial scales within and between three geographically separated cold seeps, the Central pockmark area, the Amon and the Amsterdam, all located in the Eastern Mediterranean area. The replicated sampling of several reduced habitats at each seep allowed to elucidate the most important scale of turnover. The spatial scales included here range within habitat (centimeters, micro-scale), within a cold seep (10s to 100's of meters, meso-scale) and between different seeps (10 to 100s of kilometers, macro-scale).
The results show that a typical cold seep fauna was found in all reduced samples. Compared to the reference samples, nematode densities were generally higher, with a low genus diversity, and a high dominance of only a few species, some of them being present in all three seep areas. When determining the scale of turnover using relative genera proportions, it appeared that the highest turnover rate was present between seeps (macro-scale). However, calculating the turnover based on presence/absence transformed nematode genera data showed the highest turnover rate between replicate samples (micro-scale) and habitats of the same seep (meso-scale). This shows that nematode assemblages are patchily distributed, even in a single habitat, and implicates that the sampling effort during sampling campaigns should be focused on replicate sampling and multiple habitats of the same seep. This way a more complete image of the present nematode community will be obtained.