Inner diameter core = 5.4 cm => surface area = 22.89 cm**2. Samples analyzed by Donato Giovannelli (mailto:donato.giovannelli@an.ismar.cnr.it) and Manini Elena (mailto:e.manini@ismar.cnr.it). Total protein concentration was determined on sediment sub-samples according to Hartree (1972, doi:10.1016/0003-2697(72)90094-2). Protein concentrations (PRT) were expressed as bovine serum albumin (BSA) equivalents. Total carbohydrates were analysed according to Gerchakov and Hatcher (1972, doi:10.4319/lo.1972.17.6.0938) and expressed as glucose equivalents. Total lipids were extracted from the sediment by direct elution with chloroform and methanol (1:1 v/v) according to Bligh and Dyer (1959, doi:10.1139/o59-099) and then determined according to Marsh and Weinstein (1966, http://www.jlr.org/content/7/4/574). Analyses were performed spectrophotometrically. Carbohydrates (CHO), proteins and lipid (LIP) concentrations were converted into carbon equivalents using the conversion factors 0.40 and 0.49 and 0.75 mg C mg-1, respectively, and normalised to sediment dry weight Fabiano et al. (1995, doi:10.1016/0278-4343(94)00088-5), Danovaro et al. (1999, doi:10.1016/S1385-1101(99)00024-6). The ratio between PRT and CHO (PRT/CHO) was considered as indicative of the aging of the organic matter, Pusceddu et al. (1999, doi:10.1023/A:1003690313842). Biopolymeric organic C (BPC) was calculated as the sum of the C equivalents of proteins, lipids and carbohydrates.