engleski

Influence of nutrients and salinity on heterotrophic and coliform bacteria in the shallow, karstic Zrmanja Estuary (eastern Adriatic Sea)

Spatial and seasonal distribution of heterotrophic bacteria (HB), proteolitic bacteria (PB) and total coliform bacteria (TC) was determined in relation to physical-chemical parameters in the karstic, highly stratified Zrmanja Estuary, eastern Adriatic Sea, in the period February to December 2000. A slight wastewater discharge resulted in increased abundance of HB, PB and TC bacteria. Abundances decreased from surface to the bottom. The autopurification was detected in the seaward 6.2 km section of the estuary, and expressed as the decrease of TIN (26%), HB (83%), PB (753%) and TC (2168%), as well as increase of water transparency (8%). Higher autopurification of water appeared during higher summer temperatures. During lower riverine water inflow, abundances of bacteria were reduced. Salinity was important environmental factor which controlled bacterial numbers. The estuary was mostly enriched with inorganic nitrogen from the Zrmanja River. Seawater was indicated as a considerable source of orthophosphates. Low concentrations of orthophosphates and high Redfield ratios indicated phosphorus as a strong limiting factor for the heterotrophic bacterial growth. Low bacterial abundances and nutrient concentrations indicated oligitrophic conditions in the upper reach of the Zrmanja Estuary.

CFU; estuary; heterotrophic; proteolytic; total coliform bacteria; Adriatic Sea

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