Nematode diversity patterns at different spatial scales in bathyal sediments of the Mediterranean Sea

S Bianchelli,A Pusceddu,C Gambi,R Danovaro,M Mea

doi:10.5194/bg-10-5465-2013

Abstract

Abstract. Understanding biodiversity patterns and how they are driven at different spatial scales is a crucial issue in ecological studies. This is particularly evident for the deep sea, the largest biome of the biosphere, where information on the scales of spatial variation is very scant. Here, we investigated deep-sea nematodes species richness, turnover and functional diversity, and life strategies at different spatial scales (from local to macro-regional) to identify the factors that shape regional (γ) and macro-regional (ε) deep-sea diversity. This study was conducted in several deep-sea habitats (canyons, open slopes, deep-water corals, and bathyal plains) over > 2000 km across the whole Mediterranean Basin, at a bathymetric range comprised between ca. 600 and 1300 m. Our results indicate that the patterns of local (α) diversity across the deep Mediterranean follow the gradients of the trophic conditions, which decrease from the western to the eastern basins. For all of the sites and habitats, the α diversity is generally low. Conversely, the turnover diversity changes significantly among habitats (β diversity) and between regions (δ diversity), showing values of dissimilarity (based on species presence/absence matrixes) between 59 and 90% for β diversity and between 81 and 89% for δ diversity. This suggests that patterns and values of γ and ε diversities in the deep Mediterranean Sea are related to turnover diversity among habitats and between regions (β and δ diversities), rather than to the local biodiversity (α diversity). These results indicate also that the differences in β and δ diversities are even more important than those in α diversity for the comprehension of the drivers of biodiversity in the deep Mediterranean Sea. We conclude that the presence of different habitats and gradients in environmental conditions, by promoting a high turnover diversity across the Mediterranean Sea, may play a crucial role in the levels of γ diversity of deep-sea nematodes.

Highlights

Hydrology and A comprehensive undersEtanadrintghoSf tyhespteattmerns of biodiversthiteyserepqautitreersnsthaendidoenf ttihfiecabtiioondiSvoefcrstihieteyndccroivmeepsrsontehnattsgtehnaetraretespond to these drivers
The 1-index of trophic diversity (ITD) shows no differences between different habitats in all the investigated regions (ANOVA ns; Table 3) whereas the maturity index (MI) shows significant differences among habitats in the eastern Mediterranean Sea (ANOVA, P < 0.05; Table 3), with the highest value reported from one of the bathyal plains
The present study allowed for the first time to analyse the patterns of α, γ and ε diversities, turnover β and δ diversities and functional diversity patterns of deep-sea nematodes across the Mediterranean Sea, comparing different kinds of habitats, at different spatial scales

Summary

Introduction

Hydrology and A comprehensive undersEtanadrintghoSf tyhespteattmerns of biodiversthiteyserepqautitreersnsthaendidoenf ttihfiecabtiioondiSvoefcrstihieteyndccroivmeepsrsontehnattsgtehnaetraretespond to these drivers. The drivers of local (α) and habitat turnover (β) diversities are likely to be different, as α diversity is generally associated with high abundance and high resource availability, whereas β diversity can be more sensitive to the heterogeneity of the habitat and/or of the resource distribution (Lambshead et al., 2002; Soininen et al, 2008; LSevoinliedt aEl.,a2r0t1h0). Deep-sea ecosystems represent the most extensive biome on Earth, as they cover ca. Despite the typically low abundance of the fauna of deep-sea ecosystems, their evenness and expected species richness are amongst the highest on Earth (Danovaro et al, 2010).

Methods

Results

Conclusion