Microbial dynamics on decaying leaves in a temporary Moroccan river. II - Bacteria

Seasonal variations of bacterial abundance on dead leaves decaying both in air and water, as well as microbial Electron Transport System (ETS) activit y, were investigated in a Northeastern Moroccan temporary river, Oued Cherr aa. Bacteria were counted using epifluorescence microscopy after sonication , and DAPI and acridine orange staining. ETS activity was measured with a s pectrophotometer by the reduction of INT to INT-formazan. The results point out the overwhelming influence of water on bacterial distribution: bacteri a were most abundant and larger during the flowing phase of the river and i n a permanent pool. ETS activity on leaves was higher in water than in air, and during submersion it was higher in the permanent than in the temporary sites. Some temporal correlations were found with temperature and dissolve d organic matter. Bacterial density peaked in May, and ETS activity in June . These trends explain a great part of the breakdown rates described from t he same leaf packs in a former paper.