engleski

Microbial communities associated with marine snow/aggregates

The massive accumulation of mucilaginous aggregates occasionally occurs in the northern Adriatic. Frontal zone related to mucilage events develops in the late spring/summer period due to a combination of eastward transport of the freshened waters formed in the River Po delta region and intrusions of high salinity oligotrophic waters from the southern Adriatic. Complex internal hydrodynamics inside the encounter of these two different ecosystems with numerous gradients of salinity, production and nutrients causes the structural and physiological changes within autotrophic and heterotrophic microbial community. The aggregates differ in the composition and growing stage of their contained phytoplankton, bacterial contribution and the condition of bacterial growth, in relation to aggregate age and size. Focused on freshly formed aggregates and encounters of different water bodies where mucilages were regularly found, the earliest phase of aggregate formation was reconstructed and the most important factors that lead to mucilage formation defined. The similarity between bacterial communities of fresh aggregates and oligotrophic high-salinity water, suggested their common origin and involvement in the formation of aggregates. In contrast, the origin of the water adjacent to aggregates was different from that of the other components but was similar to the halocline layer and was likely derived from northern Adriatic waters. The presence and activity of heterotrophic bacteria belonging to Alteromonadaceae, which are regularly observed on fresh aggregates, suggested that the early phase of aggregate formation corresponds to an abrupt change of environmental conditions due to the mixing of central and northern Adriatic waters.

mucilage events; marine snow; bacteria; Northern Adriatic

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