Il Mar Piccolo di Taranto: osservazioni preliminari dei nutrienti all'interfaccia acqua-sedimento

In this paper we report some preliminary results from an experiment to evaluate oxygen and nutrient benthic fluxes performed in April 1999 in the Primo Seno of the Mar Piccolo of Taranto. The basin is liable to periodic anoxic crisis induced by high nutrient inputs. The sediment was characterised by grain-size, mineralogical and biogeochemical analyses (organic and inorganic C, total N, organic and inorganic P) carried out in a sediment core collected in the basin. In the same site dissolved benthic fluxes (PO4, NH4, NO2, NO3, Si(OH)4, TCO2, O2, Fe, Mn, Ca, Mg) were carried out by benthic chamber. The sediment is mainly silty-clay (73%) with organic carbonate fragments and high organic matter (organic C= 4%) still very reactive (C/N=9.9). Benthic fluxes were positive for NH4, NO2, TCO2, PO4, Si(OH)4 and Mn and negative for O2 and NO3. Furthermore benthic chamber data showed a difference between daytime and night fluxes for O2, NO3, NO2, e TCO2. Besides benthic fluxes indicated reactive organic matter degradation processes, due to dissolved oxygen and nitrate consumption, and dissolution of diatom skeletons, due to positive fluxes of Si(OH)4. The Mn positive flux indicates reducing environment little down to the sediment-water interface.