Benthic community metabolism and microbial dynamics in the Gulf of Trieste (Northern Adriatic Sea)

Abstract

Benthic O sub(2)-fluxes of sublittoral sediments were measured in situ using continuous recording by polarographic O sub(2)-sensors. Three stations (7, 15, and 22 m deep) were investigated at ca 2 mo intervals in the Northern Adriatic Sea over a 19 mo period. High chl a contents of the sediments were found in spring (March, April) and fall (September, October) while sediment bacterial numbers fluctuated in an inconsistent pattern. Porewater dissolved organic carbon (DOC) exhibited strong seasonal variation with highest concentrations in September (20 mg Cl super(-1)); subsequently porewater DOC declined to ca 5 mg Cl super(-1) (March-April). In general, porewater DOC increased slightly with depth down to the 10-15 cm horizon. Benthic respiration was found to be temperature dependent; below 10 degree C about 6 mg C m super(-2) h super(-1) were respired while at 20 degree C the rate was 17 mg C m super(-2) h super(-1). Microphytobenthos gross primary production (GPP) was detected even at the deepest station and remained fairly constant from March to September (ca 100 mg C m super(-2) d super(-1)).