PHOSPHORUS SOURCES FOR AQUATIC MACROPHYTES IN RUNNING WATERS - WATER OR SEDIMENT

In the Alsace Rhine floodplain, a good relation between the macrophyte communities and the nutrient concentrations in water was established, arguing the importance of the water column in the nutrition of aquati c plants. In this paper, we precise the relative importance of the wat er column and the sediment in the phosphorus nutrition of three aquati c macrophytes in running water system : Elodea nuttallii, Elodea canad ensis, Callitriche obtusangula. We study the relation between the tota l phosphorus in plant, the phosphorus content in sediment and the phos phate concentrations in water, We show that the annual mean value of p hosphorus content in plant is strongly correlated to the annual mean c oncentration of phosphate in water for all the three species. In contr ast, there is no definite relation between P-plant tissue and the conc entration of total P in the sediment.