[1] Univ Piemonte Orientale Amedeo Avogadro, Dipartimento Sci Ambiente & Vita, I-15100 Alessandria, Italy
[2] Plymouth Marine Lab, Plymouth, Devon, England
[3] Alfred Wegener Inst Polar & Marine Res, D-2850 Bremerhaven, Germany
[4] Univ Genoa, Dipartimento Biol, Genoa, Italy