Variations saisonnières de l'activité de la phosphatase alcaline des communautés planctoniques bactériennes et algales dans le lac réservoir Allal El Fassi, Maroc

Abstract

Seasonal and vertical variations of alkaline phosphatase activity (APA) of the bacterial and algal planktonic communities have been studied in the mesotrophic Allal El Fassi reservoir located on the Sebou river. Samples were collected at differents depths from March to December 1998. Total APA (0.107 - 1.780 mmol PNP 1-1 h-1) was exclusively associated with the size fraction 0.22-100 μm. Free APA associated with the dissolved fraction (< 0.22 μm) was not detected. In the superficial layers, more than 60 % of APA was correlated with the 0.22-0.65 μm size fraction. In deeper layers, more than 58 % of total APA was associated with 0.65-100 μm size fraction and was significantly correlated with algal parameters (algal counts, chlorophyll a). The lack of correlation between phosphorus (P-PO43- and P-PT) and total APA suggests the independance of phosphorus to APA.