Effects of the urban environmental conditions on the physiology of two biological indicators

Abstract

Response to air pollution was assessed for lichen Evernia prunastri (L.) Ach. and the moss Ptilium crista-castrensis (Hedw.) DeNot. Samples were collected from a relatively clean remote area (Birštonas) and transplanted to a control site and three areas reflecting the different urbanization levels: urban, suburban and residential areas. Transplants were exposed for 1- and 2-month periods. Concentrations of gaseous pollutants (NO, NO2, SO2) were monitored by air monitoring stations. Differences in response of fluorescence, chlorophylls contents, MDA and injuries of cell membranes were observed among the two species and between the sites. Transplants of P.crista-castrensis from urban sites showed a decrease in chlorophyll a fluorescence. The integrity of cell membranes was also more damaged in the transplanted moss samples than in lichen. Significantly higher oxidative stress was induced in the transplants at urban and residential sites in the beginning of transplantation period (after 1 month) but such trend was not characteristic after 2 months. Since SO2 concentrations were relatively low but they were negatively correlated with chlorophyll content in moss samples. There was a linear relationship between SO2 concentration and MDA content of lichen and moss samples exposed in urban environmental conditions. Chlorophyll a and b content in mosses was positively related with nitrogen oxides while lichen showed the opposite trend. Results fit with the known ecological requirements of the studied species: E.prunastri being characteristic to relatively dry and warm sites, P.crista-castrensis being typical to moister and cooler sites. The results on transplants vitality showed that lichen is more suitable for bioindication studies with changes physiological parameters while moss was more sensitive to pollutants and site condition.