Summary

Deep-sea sediments cover about 65% of the word surface and play an important part in biomass production and biogeochemical cycle on a global scale. These processes are largely mediated by benthic prokaryotes, which use organic detritus for biomass production and respiration.

IP2 will investigate the diversity, spatial distribution, and abundance of deep-sea prokaryotes and macrofaunal species in selected areas of the Mediterranean Sea and the Atlantic Ocean. This will allow describing biogeographic patterns of some dominant species across the Mediterranean Sea and the adjacent Atlantic Ocean, and analysing these in relation with geomorphological barriers (Gibraltar Strait and Sicilian Sill) and gradients of biotic (e.g. nutrient availability) and abiotic (e.g. thermohaline characteristics, sediment dynamics) variables. The input of the CNR-ISMAR to the CRP include two main objectives:

- To investigate the spatial patterns of diversity and activity of deep-sea prokaryotes (Bacteria and Archaea) in terms of biomass, C production, metabolism and degradation rates in the deep-sea Mediterranean Sea and the adjacent Atlantic Ocean. A special attention will be also posed in evaluating the role of viruses (viral shunt) in controlling/shaping relationship between benthic biodiversity and ecosystem functioning.

- To study the macrofaunal biodiversity in relation with physical/environmental gradients across the deep-Mediterranean Sea.

Work plan

Field work:

CNR-ISMAR leaded a Mediterranean cruise by R/V Urania in spring-summer 2008 in the central and eastern basin. Another cruise is planned in spring-summer of 2009 in western Mediterranean basin. Some deep-sea selected areas will be sampled in order to focus on different nutrient availability and sediment/slope conditions. The two cruises will cover a wide geographical area (>1000 km). At each site, in order to avoid pseudo-replication, 3 to 5 independent deployments (box corers and/or multicorer) will be carried out. This hierarchical sampling strategy will provide the opportunity to assess the pattern of spatial variability in prokaryote and macrofaunal abundance, biomass and diversity. The analysis of longitudinal gradients in hydrological and phsyico-chemical conditions will provide background information for testing the hypothesis of gradient/biodiversity relationships.  The same sampling strategy will also help to assess spatial variability in the main ecosystem functioning processes that will include measurements of prokaryote C production and extracellular enzymatic activity.

Analyses:

1. Prokaryotic biodiversity, community structure and biomass: will be investigated using epifluorescence microscopy, CARD-FISH (Catalysed Report Deposition-Fluorescence in situ Hybridization) and molecular fingerprinting technique (ARISA for Bacteria and T-RFLP for Archaea)

2. Deep-benthic prokaryotic metabolism: will be investigated in terms of extracellular enzymatic activities and heterotrophic C production in the sediments.

3. Benthic viral abundance, production and decay: will be investigated through epifluorescence microscopy and dilution techniques.

4. Macrofaunal biodiversity, community structure and biomass: will be investigated using a classical taxonomic approach and standard techniques.

Retrospective data available:

Historical information for microbial variables will be obtained from the TransMed cruise (1999) of the MATER project (10 deep-sea sites at 3000-4000 m depth crossing the entire Mediterranean basin) and others collected during the ADIOS project (2001; 2 deep-sea sites at 3000 m depth in covering both Mediterranean basins) and another TransMed cruise in the frame of MEDGOOS in 2006. Time series are available at 1000 and 1600 m depth in the Eastern Mediterranean sea. Moreover, others sample collected in the Portuguese Margin will be obtained during the HERMES project (2005/06;  deep sea sites at 1500-3000 m). For the benthic fauna will be available sample of the Sea of Crete (1999). Environmental factors will be compared with data collected during the cruise activities planned in 2007 (VECTOR project; 10 deep-sea sites at 3000-4000 m depth crossing the entire Mediterranean basin) and 2008 (HERMES project, 10 deep-sea sites at 3000-4000 m depth crossing the entire Mediterranean basin).