Use of lichens as bioindicators of contamination by agrochemicals and metals

Abstract

The presence or absence of lichens serves as an indicator of the condition of an ecosystem and the degree to which it is contaminated by various agents, such as agrochemicals and metals. Evaluating the use of lichens as bioindicators of agrochemical contamination could provide a more comprehensive perspective on current contamination levels. Monitoring was, therefore, carried out over a four-month period in two study areas: a well-conserved control area and another treated area surrounded by agricultural crops. Data on the presence and abundance of lichens in each study area were recorded at 10 sampling points, a procedure that was repeated 16 times (every 15 days), and concentrations of heavy metals and “organophosphate” agrochemicals in the lichens collected were measured by means of gas chromatography. Generalized linear mixed models were used to assess abundance and richness, while general linear mixed models were used to attain Shannon diversity and Simpson dominance indices. Moreover, a multivariate analysis was performed in order to compare the lichen communities in both areas. The results indicated differences between the control and treated areas in terms of abundance and Simpson's dominance index, while no differences were found for the richness and diversity models. The PERMANOVA analysis also showed differences between the lichen communities in the two areas. The results also demonstrated that “Canoparmelia caroliniana” bioaccumulated metals in both areas. Finally, the concentrations of agrochemicals were higher in the treated area, and included toxic substances such as Methyl Parathion and Parathion, which are prohibited in Ecuador. In conclusion, the research underscores the importance of lichens as precise indicators of environmental health and contamination by agrochemicals and metals.