Experimental control tests of Pistia stratiotes L., an invasive aquatic plant of lentic habitats (Fez, Morocco)

Abstract

Invasive alien aquatic plants are endangering local ecosystems in Morocco and require early and cost-effective interventions. Water lettuce (Pistia stratiotes L., Araceae) has progressively invaded the Wadi Al Jawahir (Fez, Morocco) over the last decade even with all the control measures implemented. This work aimed to test in mesocosms during 7 weeks, under controlled temperature, relative humidity, lighting, and photoperiod, the effect of three control methods of P. stratiotes: 0.14% liming, drainage and surface aeration at 370 L·h − 1. Plant biometric and functional parameters and the physicochemical and bacteriological quality of the growing waters were used to evaluate the effect of these control methods on the development of Pistia. The three methods tested limit both sexual reproduction of this plant species by preventing its flowering, and its vegetative propagation through decreasing biomass accumulation. Under favourable conditions (polluted eutrophic waters), P. stratiotes plants reached the flowering stage, and showed a very highly significant growth compared to the seedling stage, with an average height of 19.9 ± 8.97 cm, vs. 7.06±1.21 cm and 6.32±2.41 cm under surface aeration and drainage circumstances in the same order. P. stratiotes also showed biomass reduction with rates of 100%, 71.49%, and 44.5% respectively in application of liming, drainage and surface aeration. These experimental reduction rates suggest possibilities for future pilot-scale application of the proposed control methods as alternatives and/or in combination with existing ones.