BIOMASS PRODUCTION AND NPK RETENTION IN MACROPHYTES FROM WETLANDS OF THE TINGITAN PENINSULA

A field study was undertaken on Phragmites australis (Cav.) Trin. Ex S teudel, Typha angustifolia L., Sparganium erectum L., Juncus acutus L. , J. maritimus Lam., Scirpus litoralis Schrader, S. maritimus L., Lemn a gibba L. and L, minor L. communities, in order to evaluate and compa re their biomass production and NPK retention rates in unpolluted and polluted wetlands of northwest Morocco. This was undertaken to select species with the potential for macrophyte-based wastewater treatment s ystems. The highest total biomass values were observed for ir: angusti folia, P. australis and S. erectum, which accumulated 56.5, 52.7 and 2 0.1 t dry weight ha(-1) year(-1), respectively. They also retained in their tissues nitrogen and phosphorus at the rates of 922, 561 and 375 kg N ha(-1); and 114, 72.1 and 84.8 kg P ha(-1), respectively. The ab ove-ground annual net productivity estimated under Mediterranean clima te exceeds that reported for Phragmites australis occurring under an o ceanic climate. But it is similar if compared to the continental clima te for Sparganium erectum and Typha angustifolia. As for NPK accumulat ion, Phragmites australis and Typha angustifolia did not differ in the ir natural sites, or according to P. australis applied in constructed wetlands for wastewater treatment. (C) 1998 Elsevier Science B.V. All rights reserved.