Extracellular enzyme activity and dynamics of bacterial community in mucilaginous aggregates of the northern Adriatic Sea

Organic matter limitation was observed only on stringers-total C incorporated raised to 0.96 mg C L− 1 after PNG addition. Macroflocs release of refractory compounds leads to DOC accumulation (73 μM DOC) contributing to inflate the pool of refractory DOC in the surrounding waters. Several evidences, including different monosaccharide composition of stringers and macroflocs (glucose 15% and 56% on stringers and macroflocs, respectively), bring to the conclusion that stringers are in an older stage in comparison with macroflocs. Community composition described by fluorescence in situ hybridization did not show significant differences between free-living and attached bacteria but it was modified by the different enrichment conditions: Cytophaga-Flavobacteria increased after inorganic nutrients enrichments while organics advantaged γ-Proteobacteria.