(E)MERGING DIRECTIONS ON AIR POLLUTION AND CLIMATE CHANGE RESEARCH IN MEDITERRANEAN BASIN ECOSYSTEMS The effects of experimentally supplied lead nitrate on three common Mediterranean moss species Jennifer Cogolludo 1 & Belén Estébanez 1 & Nagore G. Medina 1 Received: 15 December 2016 /Accepted: 8 May 2017 /Published online: 19 May 2017 # Springer-Verlag Berlin Heidelberg 2017 Abstract We assess here, through an experimental simulation using lead nitrate, the response to lead deposition of three common Mediterranean bryophyte species in the family Pottiaceae. Five concentrations of lead nitrate (from 0 to 10 -3 M) were sprayed for 4 months on plants belonging to Tortula muralis (reported as toxitolerant), Syntrichia ruralis (medium-tolerant), and Tortula subulata (less tolerant). The three species showed a remarkably high tolerance to lead ni- trate, with a low incidence of damage even at concentrations as high as 10 -4 M. The maximum concentration (10 -3 M), although resulting eventually in serious damages in the game- tophyte of the three species (high mortality rates in S. ruralis and T. subulata, or a significant percentage of damaged tissue in T. muralis), did not prevent the production of sporophytes in the two species with fertile samples (T. muralis and T. subulata). Growth parameters show limited value as bioindicators of lead deposition, as they only show clear ef- fects at very high concentrations. Besides, we identified the existence of a lead exclusion strategy mediated by mucilage using histochemical analyses and scanning electron microsco- py combined with energy-dispersive X-ray spectroscopy. This mechanism can hamper the usefulness of these mosses in quantitative estimation of lead deposition. Keywords Simulated lead deposition . Moss bioindication . Exclusion mechanisms . Mucilage Introduction Bryophytes have been frequently used as indicators of environ- mental pollution, and more specifically, they have been consid- ered excellent tools to monitor atmospheric metal pollution (Onianwa 2001; Giordano et al. 2004; Zechmeister et al. 2007; Harmens et al. 2010, 2015a). Alterations in the physiog- nomy, physiology or reproductive state of the species and/or the properties of bryophyte communities have been successful- ly used as indirect indicators of the concentrations of heavy metals in the environment (see for example, the review of Onianwa 2001 and references therein). However, we lack rel- evant information on the biology of many species, their level of sensitivity, and the expected responses under different pollution concentrations, especially in the Mediterranean region. Besides, the sensitivity categories (Dierβen 2001; Hill et al. 2007) are usually established taking into account solely the presence or abundance of the species in urban catalogs. This does not allow separating the effect of the different pollutants and other typically urban characteristics that are known to be detrimental for the growth and development of bryophytes (such as drought conditions or habitat alterations). Bryophytes have also been employed in quantitative esti- mations of atmospheric deposition of heavy metals. They are said to be good biomonitors because they absorb water, nutri- ents, and pollutants over all their surface, so a predictable relationship of metal content in the tissues with atmospheric deposition is more likely in bryophytes than, for example, in vascular plants. In fact, some selected species have been al- ready used for systematic monitoring of pollution by heavy metals (Gerdol et al. 2002; Ötvös et al. 2003; Zechmeister Responsible editor: Philippe Garrigues Electronic supplementary material The online version of this article (doi:10.1007/s11356-017-9220-1) contains supplementary material, which is available to authorized users. * Nagore G. Medina nagore.garcia@uam.es 1 Dpto. Biología, Fac. Ciencias, Universidad Autónoma de Madrid, Madrid, Spain Environ Sci Pollut Res (2017) 24:26194–26205 DOI 10.1007/s11356-017-9220-1