Optimizing Moss and Lichen Transplants as Biomonitors of Airborne Anthropogenic Microfibers

SIMPLE SUMMARY: Environmental pollution due to the presence of anthropogenic microfibers, including microplastics, is a problem affecting quality of life in modern society. Anthropogenic microfibers are ubiquitous, produced by a multitude of processes, and harmful to organisms and ecosystems. In this article, we present the results of an experiment aimed at optimizing the use of transplanted mosses and lichens as biomonitors (i.e., organisms capable of accumulating or reacting to the presence of pollutants) of anthropogenic microfibers. We found that the moss H. cupressiforme is preferable to the lichen P. furfuracea, especially when exposed without a covering net. ABSTRACT: Anthropogenic microfibers (mfs) are synthetic particles composed of cellulose (cotton, rayon, acetate, etc.) or petrochemical-based polymers (i.e., microplastics—MPs) that are less than 5 mm in length. The accumulation of mfs, including MPs, in the moss Hypnum cupressiforme and the lichen Pseudevernia furfuracea was compared in a transplant experiment lasting 6 weeks. We also tested the effects of the bag used for transplants on the accumulation of mfs. Anthropogenic particles trapped by both biomonitors were mostly filamentous (99% mfs), and their number was overall higher in the moss (mean ± s.d. 102 ± 24) than in the lichen (mean ± s.d. 87 ± 17), at parity of sample weight. On average, mfs found in lichen were significantly longer than those found in moss bags, suggesting that lichens are less efficient at retaining smaller mfs. Exposure without the net yielded a higher mfs number accumulation in both species, indicating that “naked” transplants provide greater sensitivity. The calculation of daily fluxes evidenced a loss of mfs in the lichen, suggesting the presence of more stable bonds between moss and mfs. Raman microspectroscopy carried out on about 100 debris confirms the anthropogenic nature of mfs, of which 20% were MPs. Overall results indicate that moss is preferable to lichen in the biomonitoring of airborne mfs especially when exposed naked.