Relationships between water chemistry and macrophyte chemistry in lotic and lentic environments

A two-year study was carried out a) to describe the particular ecological situation in the Parana River and its floodplain, b) to evaluate the role of Eichhornia crassipes (MART.) SOLMS. (floating macrophyte) and Paspalum repens BERG. (rooted macrophyte) as nutrient reservoirs; c) to assess whether the lotic factor has an influence on the chemical characteristics of plants, and d) to study the influence of vegetation on the physicochemical quality of water. The importance of the E. crassipes rhizosphere as a nutrient retainer was demonstrated. E. crassipes absorbs soluble reactive phosphorus and ammonia for its development during the spring-summer period, but this floating plant has no influence on nutrient concentrations in water during the winter. P. repens had an influence on nutrient concentrations in the water, but a particular pattern could not be established. In both environments, the aquatic plants studied had no significant influence on major ion concentrations in the water during the period considered (ANOVA, two-way, p<0.05). Moving water has a positive influence upon the growth of P. repens. Sediment can be considered as the major nitrogen compartment, water being the second in importance. Sediment must also be considered as the main reservoir for phosphorus followed by macrophytes.