Unravelling the environmental drivers of deep-sea nematode biodiversity and its relation with carbon mineralisation along a longitudinal primary productivity gradient

[摘要] Alongside a primary productivity gradient between the Galicia Bank region inthe Northeast Atlantic and the more oligotrophic eastern Mediterranean Basin,we investigated the bathymetric (1200–3000 m) and longitudinal variation inseveral measures for nematode taxon (Shannon–Wiener genus diversity,expected genus richness and generic evenness) and functional diversity(trophic diversity, diversity of life history strategies, biomass diversityand phylogenetic diversity). Our goals were to establish the form of therelation between diversity and productivity (measured as seafloor particulateorganic carbon or POC flux), and to verify the positive and negative effectof sediment particle size diversity (SED) and the seasonality in POC flux(SVI), respectively, on diversity, as observed for other oceanographicregions and taxa. In addition, we hypothesised that higher taxon diversity isassociated with higher functional diversity, which in turn stimulatesnematode carbon mineralisation rates (determined from biomass-dependentrespiration estimates). Taxon diversity related positively to seafloor POCflux. Phylogenetic diversity (measured as average taxonomic distinctness) wasaffected negatively by the magnitude and variability in POC flux, andpositively by SED. The latter also showed an inverse relation with trophicdiversity. Accounting for differences in total biomass between samples, weobserved a positive linear relation between taxon diversity and carbonmineralisation in nematode communities. We could, however, not identify thepotential mechanism through which taxon diversity may promote this ecosystemfunction since none of the functional diversity indices related to bothdiversity and nematode respiration. The present results suggest potentialeffects of climate change on deep-sea ecosystem functioning, but further alsoemphasise the need for a better understanding of nematode functions and theirresponse to evolutionary processes.

[学科分类] 地球化学与岩石