Morphophysiological screening of potential organisms for biomonitoring nitrogen deposition

Abstract

• Local species of different functional groups can be screened in regions of interest. • This proof-of-concept focused on the highly polluted megalopolis of Mexico City. • The moss Braunia secunda is a potential biomonitor of N deposition. • The moss Thuidium delicatulum experienced damage under all N treatments. • Neither Tillandsia had visual nor physiological response to simulated N deposition. The intensification of different anthropic activities has led to a doubling of the emitted reactive nitrogen species since the second half of the XX century, resulting in the increase of nitrogen deposition. This poses a major threat to global biodiversity. However, in developing countries the monitoring of atmospheric deposition has shown to be difficult. For these reasons, the aim of this study was to assess, by means of a greenhouse dose-response experiment, the biomonitoring potential of two mosses, Braunia secunda and Thuidium delicatulum , and two epiphytic bromeliads, Tillandsia recurvata and Tillandsia usneoides , which are widely distributed in Latin America. A significant increase of the phosphomonoesterase activity was observed for the mosses, particularly under a High-nitrogen treatment, a parameter that decreased for the bromeliads. In turn, the nitrate reductase activity decreased over the course of the experiment for the mosses, but it remained almost unchanged for both tillandsias. While the nitrogen content for the mosses increased, it fluctuated for the bromeliads. Braunia secunda became greener under the Low-nitrogen than under the other treatments, while the coloration for T. delicatulum turned to brown under all treatments. The tillandsias remained visually unchanged under all treatments. The mosses had a clear response to the simulated nitrogen deposition, with B. secunda being more tolerant than T. delicatulum . Neither tillandsia presented a clear response to the treatments. Thus, the moss B. secunda is a very suitable species for biomonitoring nitrogen deposition, while the other species evaluated were deemed unsuitable.