Myriophyllum alterniflorum DC., biomonitor of metal pollution and water quality. Sorption/accumulation capacities and photosynthetic pigments composition changes after copper and cadmium exposure

Watermilfoil genus Myriophyllum could be used in ecological surveys as in-situ biomonitors of metal pollution and water quality due to its ability to accumulate chemicals. The copper and cadmium sorption characteristics of Myriophyllum alterniflorum have been investigated. The Langmuir and Freundlich isotherms were used to model the metal sorption isotherms and the monolayer sorption capacities, as obtained by the Langmuir isotherm, were determined to be 13.9 mg/g and 11.1 mg/g for Cu2+ and Cd2+ respectively. Results have been compared with previous works on watermilfoils and are in accordance with those obtained on Myriophyllum spicatum. The sorption of the two metals was time-dependent and the kinetics fitted the pseudo-second-order equation well. The data were discussed in terms of ionic radii and HSAB concept. The phytotoxic effects assessed by classical (i.e. changes in biomass, node length) and photosynthetic pigments content endpoints have been investigated using chemometric techniques leading to an effect of cadmium onto photosynthetic pigments.