Abstract: To explore the effect of acid deposition and nano-ZnO on functional microorganisms in leaf litter decomposition, we assessed effects of the interaction of those two factors on the growth and function of two dominant aquatic fungi, Geotrichum candidum and Mucor circinelloides. Results showed that the coupling effect of those two factors significantly promoted the growth of G. candidum, but inhibited its enzyme activities compared to the effect of each single factor. For M. circinelloides, the coupling effect showed inhibitory role on fungal growth and enzyme activities. Therefore, G. candidum was more tolerant to the coupling effect of acid deposition and nano-ZnO, whereas M. circinelloides was more sensitive with decreases in water absorption capacity, material synthesis, and extracellular enzyme activities. The inhibitory effect would influence the role of M. circinelloides in leaf litter decomposition. The results improve our understanding of the coupling effect of acid deposition and nano-ZnO on the decomposition function of aquatic fungi.

Key words: acid deposition, nano-ZnO, coupling effect, aquatic fungi, extracellular degrading enzyme