Coastal dynamics and dissolved organic carbon in the western Sardinian shelf (Western Mediterranean)

Two surveys (March and September 2001), were carried out in the Sardinian Sea in order to investigate dissolved organic carbon (DOC) dynamics in a coastal area affected by intense mesoscale activity. DOC ranged from 38 mM to 94 mM without a clear seasonality, but with marked differences between the two surveys in the processes driving its surface distribution. Mesoscale activity mainly controlled its distribution, with opposite behavior in the two periods; in fact, in correspondence of an upwelling, a DOC decrease was observed in March, while a DOC increase was observed in September. Stratification affected DOC distribution in September, but with lower strength than expected. The occurrence of deep chlorophyll maximum ~40 m below the thermocline, suggests that most of DOC was produced below the mixed layer and so it cannot be accumulated above the thermocline. In the intermediate and deep layers of this area the link among DOC and circulation, age and origin of the different water masses was confirmed.