The scuba-diving sampling method was used in the northern Adriatic during the last two years (1992-1993). Benthic fluxes of dissolved N, Si, P nutrients, and alkalinity, dissolved inorganic C (DIC) and O 2 where misured monthly over 16 months periods from sediments in the Gulf of Trieste, using direct sampling and laboratory incubated flux chambers at in situ temperature. The experiments were performed in the dark since previous studies showed the important utilization of released nutrients by benthic microalgal mat. The estimated yearly average fluxes were: O 2 =-19.3±8.2, DIC=13.7±9.6, NO 3 =-0.04±0. 16, NH 4 =0.3±0.4, P04 =-0.001±0.01, Si =0,9 ± 1.1 mmol m-2 d-1 , showing strong temporal fluctation. The highes effluxes of all nutrients and DIC were observed in the summer period but small DIC efflux ang NH4 , Si and P04 influxes in the late winter. Only NH4 (ca 50%) and Si (ca 70% ) fluxes were significantly direct temperature dependent. This suggests that the rate of downward input and quality of sedimented organic matter (autochtonous and allochtonous) were superimposed on the temperature fluctation. High DIC, NH4 and Si effluxes observed in Ma y 1993 during low temperature was due to degradation of sedimented organic matter produced by early spring microphytobenthonic bloom about 6 weeks before while the autumn phytoplanktonic bloom was simultaneously reflected in enhanced benthic fluxes due to higher temperature. The nutrient fluxes observed were not significant l y linked to O 2 consumption suggesting that also anaerobic oxidation processes were important at the sediment-water interface in the Gulf.
METODOLOGIE SUBACQUEE PER LO STUDIO DELLA VARIAZIONE ANNUALE DEI FLUSSI BENTICI E DEI NUTRIENTI (N, SI, PI) IN ACQUE COSTIERE (GOLFO DI TRIESTE, NORD ADRIATICO)
DEMURO, SANDRO;
1997-01-01
Abstract
The scuba-diving sampling method was used in the northern Adriatic during the last two years (1992-1993). Benthic fluxes of dissolved N, Si, P nutrients, and alkalinity, dissolved inorganic C (DIC) and O 2 where misured monthly over 16 months periods from sediments in the Gulf of Trieste, using direct sampling and laboratory incubated flux chambers at in situ temperature. The experiments were performed in the dark since previous studies showed the important utilization of released nutrients by benthic microalgal mat. The estimated yearly average fluxes were: O 2 =-19.3±8.2, DIC=13.7±9.6, NO 3 =-0.04±0. 16, NH 4 =0.3±0.4, P04 =-0.001±0.01, Si =0,9 ± 1.1 mmol m-2 d-1 , showing strong temporal fluctation. The highes effluxes of all nutrients and DIC were observed in the summer period but small DIC efflux ang NH4 , Si and P04 influxes in the late winter. Only NH4 (ca 50%) and Si (ca 70% ) fluxes were significantly direct temperature dependent. This suggests that the rate of downward input and quality of sedimented organic matter (autochtonous and allochtonous) were superimposed on the temperature fluctation. High DIC, NH4 and Si effluxes observed in Ma y 1993 during low temperature was due to degradation of sedimented organic matter produced by early spring microphytobenthonic bloom about 6 weeks before while the autumn phytoplanktonic bloom was simultaneously reflected in enhanced benthic fluxes due to higher temperature. The nutrient fluxes observed were not significant l y linked to O 2 consumption suggesting that also anaerobic oxidation processes were important at the sediment-water interface in the Gulf.
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