Biomonitoring of nine elements by the lichen Xanthoria parietina in Adriatic Italy: a retrospective study over a 7-year time span.

The results of long-term biomonitoring of nine elements (Cd, Cr, Ni, Pb, V, Cu, Zn, Fe and Al) with the epiphytic lichen Xanthoria parietina over a seven year time span are reported. A total of 51 sampling stations were monitored in two surveys, obtaining information about heavy metal concentrations in a large area characterized by a high impact of industrial and urban sources of air pollution. The results showed that the approach adopted is indeed a reliable tool to assess environmental alteration, pinpointing not only the trends of the nine elements analysed but also their reciprocal correlations. As a consequence it was possible to characterize changes in air pollution composition and the common origin and behavior of several groups of elements.

Lichen biomonitoring of ammonia emission and nitrogen deposition around a pig stockfarm.

Effects of high ammonia emissions and nitrogen deposition were investigated on lichens around a pig stockfarm (ca. 7,000 animals) in central Italy. Four sites were selected along a transect at 200, 400, 1000 and 2500 m from the stockfarm, the diversity of epiphytic lichens was measured and transplanted thalli of Xanthoria parietina and Flavoparmelia caperata exposed, together with passive NH3 (diffusion tubes) samplers. Ammonia dramatically decreased from the centre of the stockfarm to the sampled sites, where it was correlated with bark pH. Total lichen diversity was not associated with either NH3 concentrations or bark pH, but the diversity of strictly nitrophytic species was highly correlated with both parameters. Physconia grisea was the best indicator species for NH3 pollution. Total N accumulated in X. parietina and F. caperata was correlated with NH3 concentrations.

Reliability of different sampling densities for estimating and mapping lichen diversity in biomonitoring studies.

Sampling requirements related to lichen biomonitoring include optimal sampling density for obtaining precise and unbiased estimates of population parameters and maps of known reliability. Two available datasets on a sub-national scale in Italy were used to determine a cost-effective sampling density to be adopted in medium-to-large-scale biomonitoring studies. As expected, the relative error in the mean Lichen Biodiversity (Italian acronym: BL) values and the error associated with the interpolation of BL values for (unmeasured) grid cells increased as the sampling density decreased. However, the increase in size of the error was not linear and even a considerable reduction (up to 50%) in the original sampling effort led to a far smaller increase in errors in the mean estimates (<6%) and in mapping (<18%) as compared with the original sampling densities. A reduction in the sampling effort can result in considerable savings of resources, which can then be used for a more detailed investigation of potentially problematic areas. It is, however, necessary to decide the acceptable level of precision at the design stage of the investigation, so as to select the proper sampling density.

Oxidative stress and usnic acid content in Parmelia caperata and Parmelia soredians (Lichenes).

High light levels together with Paraquat treatment or exposure to pollutants (e.g. SO2) can cause oxidative stress in epiphytic lichens. In some cases, a significant increase in ascorbic acid and other antioxidant metabolites, sometimes occurring in lichens only, was observed. In this study, usnic acid was measured by HPLC in Parmelia caperata and Parmelia soredians thalli treated with Paraquat, a herbicide which transfers electrons from various transport systems to oxygen, producing O2*- superoxide radicals. In light, Paraquat acts by generating active oxygen species within the chloroplast, thus simulating the oxidative component of environmental stress. The significant increase in the usnic acid content measured in P. soredians thalli (+ 36.3%) is in line with the hypothesis that it has an antioxidant action, but it is in contrast to the limited increase measured in P. caperata thalli (+ 13.7%). These apparently contradictory results confirm those found in the literature, which attribute different functions to usnic acid depending on the lichen species considered and on whether they have other detoxifying substances in their thalli. These studies are of potential application-oriented interest in relation to research into new active principles to be used in the pharmaceutical, food and cosmetic fields and/or in environmental biomonitoring.

Bioaccumulation of vanadium in the epiphytic lichen Parmelia caperata from Liguria (north-west Italy).

The concentration of vanadium was measured in 35 samples of the epiphytic lichen Parmelia caperata collected along the coast of the Ligurian Sea (Italy), in order to detect the possible bioaccumulation of vanadium due to a huge crude oil burning occurred in that area in 1991. The cartographic elaboration of data shows a pattern of distribution of vanadium concentrations according to different degrees of deviation from background condition, showing that 8 years later memory of the accident is still detectable in foliose lichen thalli.