Estimation of primary productivity from diel nitrate uptake measurements of the water hyacinth Eichhornia crassipes in an aquaculture system

The primary productivity of the water hyacinth Eichhornia crassipes was estimated from diel measurements of N03 -N uptake in an aquaculture system using a continuous, automated nutrient analyzer apparatus. Productivity values obtained by this method agreed favorably with those made by directly harvesting the biomass. Since productivity measurements based on harvesting methods would be impractical on a large scale, the use of diel nutrient uptake measurements would be a significant improvement for proper management of aquatic macrophytes in an aquaculture system. There were few diel changes in N03 -N uptake by Eichhornia, a fact which is potentially beneficial to this species not only to its ecological success in its natural ecosystem, but also to its ability to remove nutrients as a component in tertiary sewage treatment.