Deep-sea meiofaunal communities in the south-eastern Levantine basin– spatial and temporal dimensions

The present study adds temporal and spatial dimensions to the characterization of the sedimentary meiofaunal communities of the Israeli Mediterranean deep sea. Abundance calculation was based on counting sorted individuals, and species composition and diversity were evaluated by metabarcoding, using Amplicon Sequence Variant Clusters (ASVCs) as species-proxy. A method for estimating average within-species barcode variability was initially suggested and was used for clustering ASVs to ASVCs. The ASVC x sample matrix of barcode reads, was normalized to the actual counted individuals and rare ASVCs, assumed to emerge from residual DNA, were nullified. The abundance depth-related distributions supported previous indications of lateral transportation of labile organic matter from the off-Haifa shelf into the steep, canyon-rich mid-slope. Peaks of ASVC diversity indices appeared deeper in the slope at Haifa than in Tel Aviv which may be also explained by the lateral transportation, assumedly changing the depth-related distribution of a variety of ASVCs. Species composition comparisons across the two transects led to the identification of three main habitats: deep shelf, continental slope, and bathyal basin, accompanied by more delicate depth-related differences in the shelf and slope. No broad ASVC composition differences were observed between the off-Haifa and off-Tel Aviv transects in spite of the shift of ASVC diversity indices peaks to deeper parts of the slope in the off-Haifa transect. A second sampling event which included an additional sampled transect, supported the previously suggested lateral transportation via canyons and accurately distinguished spatial and temporal meiofaunal communities in the south-eastern Mediterranean.