Temperature effects on copper uptake and CO2 assimilation by the aquatic moss Rhynchostegium riparioides

Abstract

Since water temperature is a major factor influencing the development and the geographic distribution of aquatic mosses, experiments were performed to study the influence of temperature on both the physiology and the metal uptake-release ability of the species Rhynchostegium riparioides. Experiments were carried out in the laboratory in a flow-through system contaminated for 12 days by a copper solution with a mean concentration of 80 μg/L and then followed by a post-exposure period of 10 days. Denaturation of chlorophyll pigments was observed at 29°C for both the control and the contaminated organisms. The increase of water temperature from 7 to 29°C led to a decrease in moss vitality measured by CO2 assimilation but did not affect Cu uptake-release kinetics. Therefore the accumulation of Cu is not directly related to photosynthesis. Since Cu uptake by the mosses over the 22 days of exposure was not significantly influenced by water temperature, the results support the use of Rhynchostegium riparioides as an indicator of copper pollution in cases of thermal pollution or during different seasons.