BENTHIC FLUXES OF DISSOLVED INORGANIC CARBON, NUTRIENTS AND OXYGEN INTHE GULF-OF-TRIESTE (NORTHERN ADRIATIC)

Benthic fluxes of dissolved inorganic N, Si and P nutrients, alkalinit y, dissolved inorganic C (DIC), and O-2 from sediments in the Gulf of Trieste (northern Adriatic, Italy) were measured monthly in the period September 1995 - August 1996 using in situ incubated light benthic ch ambers. The highest efluxes of DIC, NH4+, PO43-, Si(OH)(4), and NO3- i nfluxes encountered in late summer - early autumn were the consequence of degradation of benthic microalgae, and in autumn mostly of sedimen ted phytoplankton. High NO3- eflux was observed in spring. Only NH4+ a nd Si(OH)(4) fluxes were significantly correlated with temperature. Th is correlation suggests that the rate of downward input and the qualit y and quantity of sedimentary organic matter (autochthonous and alloch thonous) were superimposed on the temperature fluctuations. High DIG, NH,+ and Si(OH), effluxes observed in July 1996 were due to the late s pring - early summer degradation of sedimentary organic matter produce d by benthic microalgae, while the autumn phytoplankton bloom was quic kly reflected in enhanced benthic fluxes due to higher temperature. Si gnificant correlations between NH4+, PO43- and Si(OH)(4) fluxes sugges ted their parallel regeneration and utilization at the sediment-water interface. The nutrient fluxes were linked to O-2 consumption, suggest ing that aerobic oxidation processes were important at the sediment-wa ter interface in the Gulf. The N, P and Si nutrients released from sed iment pore waters are probably utilized in benthic microalgal and bott om-water primary production. This indicates that pelagic and benthic c ommunities in the central part of the Gulf of Trieste function relativ ely independently of each other.