Drivers of deep Mediterranean megabenthos communities along longitudinal and bathymetric gradients

12 pages, 5 figures, 1 table, supplementary material in https://doi.org/10.3354/meps09333

The Mediterranean deep sea, being isothermal and longitudinally trophic-graded, is an optimal natural benchmark to test for macro-ecological patterns of species distribution. The relevance of environment-biota interactions on deep-sea megafauna in the Mediterranean Sea, a matter still neglected, is addressed here along longitudinal and bathymetric axes. Benthic and nektobenthic megafauna were collected in the 3 basins of the Mediterranean: the western (Catalan Sea and southern Balearic), central (western Ionian) and eastern (south of Crete) basins, with an otter-trawl Maireta system and an Agassiz dredge between 1200 and 4000 m depth. Simultaneously, environmental data were collected on surface production, near-bottom physical parameters, sediment grain size and carbon content. Megafaunal biomass was higher in the Catalan Sea, decreasing eastward and with depth. Species diversity and evenness were relatively constant in the western and central Mediterranean at all depths, whereas these indices decreased with depth in the eastern Mediterranean. β-diversity analyses indicated a high species turnover between areas. The 3 basins presented significantly different environmental conditions. Sediment particulate organic carbon, surface fluorescence and sediment grain size were the 3 environmental variables that best explained the distribution of megabenthos along the longitudinal Mediterranean axis. These results show that the food supply, from either the surface or from the adjacent deepsea floor, is critical in regulating the biodiversity of deep-sea Mediterranean megafauna and that this diversity is pooled region-wide. The heterogeneity of resources may be essential in maintaining these high levels of local and regional diversity

This work was funded through the BIOFUN project (CTM2007-28739-E) by the European Science Foundation, the PROMETEO Spanish national project (CTM2007-66316- C02/MAR) by the CICYT and the European Community’s Seventh Framework Programme under the HERMIONE project (Grant Agreement 226354). Geological analyses were supported by projects GRACCIE-CONSOLIDER (CSD2007-00067), REDECO (CTM2008-04973-E/MAR) and a Generalitat de Catalunya ‘Grups de Recerca Consolidats’ grant (2009 SGR 1305). S.T. was funded by a JAE-PRE-2008 grant, and E.R.L. was funded by a JAE-DOC-2008 grant, both from the Spanish Research Council (CSIC), Spain

Peer Reviewed