Diel and seasonal variations in bacterioplankton production in a hypertrophic shallow lagoon

摘要

Diel and seasonal variations in bacterial secondary production (BP) were investigated in the hypertrophic Albufera de Valencia (Spain) by measuring H-3-leucine and H-3-thymidine incorporation rates (LIR and TIR). LIR and TIR were positively correlated. Seasonal variations in the LIR:TIR ratio seemed to be related to dissolved organic carbon (DOC) availability, with higher concentrations favoring protein synthesis. The light:dark ratio of the incorporation rates of both radiotracers was close to 1. However, this ratio tended to be >1 when DOC was lower, namely in winter. A clear diel pattern in bacterial activity was found, with an increasing trend during the night hours. The opposite diel pattern was observed for DOC. BP remained similar across seasons but showed a decrease in late winter during a period of high water discharge through the lagoon and concurrent minimum chlorophyll a concentrations. A comparison between hypertrophic systems aiming to explore the upper BP limit indicated that our BP estimates were considerably high but did not surpass previous values in hypertrophic lakes