Southern Adriatic Sea, Otranto Strait and Northern Ionian Sea

Particulate total and organic nitrogen concentrations in the water column

Unconsolidated sediment corers

Sediment cores were collected by means of a Multicorer, and sliced into 0.5, 1, 2 cm thick sections. Total and organic C and total N were determined by dry combustion on a CHNS elemental analyzer (Fisons NA 2000). Subsamples for organic carbon were decarbonated using 1M HCl and dried (Hedges and Stern, 1984). Biogenic silica was extracted with 0.5 M NaOH solution at 85 C (Muller and Schneider, 1993), dissolved silica was determined spectrophotometrically (Strickland and Parsons; 1972). Sediment grainsize Sediment samples are first treated with Hydrogen peroxide in order to eliminate organic coatings. Grain size fraction > 63 mm (sand) is separated by wet If this fraction exceeds 5 %, further sand size class sorting is obtained by gravity settling through a sedimentation tube. The < 63 mm fraction is analysed by a Sedigraph 5000D (Micromeritics). Finest fraction is 0.025 mm diameter. Grain size composition is classified according to Shepard (1954)and referreed as sand, silt and clay percentages.

CNR, National Research Council, Institute of Marine Science (Bologna)
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