Nitrogen fixation associated with two cohabiting moss species expresses different patterns under Cu and Zn contamination

Abstract

Nitrogen (N ₂) fixation by moss-associated cyanobacteria is an important N source in pristine ecosystems. Previous studies have shown that moss-associated N ₂ fixation is sensitive to anthropogenic N pollution. However, we still lack understanding of the effects of other factors derived from anthropogenic sources, such as heavy metal pollution on N ₂ fixation. To test this, we collected two dominant mosses ( Pleurozium schreberi and Spaghnum palustre) from a temperate bog in Denmark and assessed their N ₂ fixation responses to simulated heavy metal pollution by adding 5 levels (plus a control) of copper (Cu, 0–0.05 mg g dw ⁻¹) and zinc (Zn, 0–0.1 mg g dw ⁻¹). Metal concentrations in both mosses increased linearly with Cu and Zn addition, but N ₂ fixation activity associated with S. palustre was to a greater extent negatively affected by both Cu and Zn additions than that associated with P. schreberi. Copper additions even promoted N ₂ fixation in P. schreberi. Hence, the heavy metal sensitivity of N ₂-fixing cyanobacteria is dependent on the host moss-species, and the vulnerability of ecosystems towards heavy metal pollution could vary depending on the dominant moss species.

Supplementary Information

The online version contains supplementary material available at 10.1007/s11356-023-28404-0.