Southern Adriatic Sea, Otranto Strait and Northern Ionian Sea

Primary production in the water column

Satellite tracking system

Photosyntetically active radiation (PAR, 400-700 nm) was measured in nEisteins as quantum energy units ( nE m-2 s-1) between dawn and dusk (hourly incident and total daily irradiation) using a LI-COR air quantum sensor (model Li-190 SA ) connected to a LI-1000 data logger (MAI 1,2,5,6,8). Before water sampling, vertical profiles of underwater irradiance were measured with a spherical quantum sensor (model LI-192 SA) (MAI 1,2) with PNF 300 (MAI 5,6), to identify the depth of the photic layer. Total primary production (14C tecnique), was measured according to the method described by Steeman and Nielsen (1952). On the basis of PAR and fluorescence profiles in the water column, water samples were collected by CTD-rosette at six depths, from the surface to the 0.1% light transmission depth. Samples of the autotrophic community were introduced into three (two light and one dark) 125 ml policarbonate bottles, inoculated with radioactive bicarbonate solution (3 nCi activity). The specific activity of radiolabelled bicarbonate was measured by counting the total activity in an aliquot of stock solution stabilized with NaOH, to prevent CO2 losses. Samples were in-situ incubated for 4 h around midday, then filtered through Millipore HA filters (0.45 nm pore size, 47 mm diameter) and the filters were rinsed with filtered seawater from the sampling site. After 12 hrs to remove inorganic 14C, filters were acidified with 500 nl 1M HCl in glass scintillation vials, dissolved in 10 mls of scintillation cocktail (Packard Filter Count) and stored in darkness. 14C analyses will be done using a liquid scintillation counter (Quantulus, LKB-Wallac).

ENEA Centro Ricerche, Frascati
Via Enrico Ferni 45
Frascati - Rome

00044
Italy