Natural UVR Does Not Affect Decomposition by Aquatic Hyphomycetes

Abstract

We performed field and laboratory experiments to evaluate the effect of solar radiation (UVR and PAR) on leaf litter decomposition, fungal biomass and sporulation rates, in the Andean Patagonia, where high UVR levels are common. Leaves of Alnus glutinosa exposed to three treatments, normal radiation (PAR + UVR), protected from UVR and protected from total radiation (SHADE) by plastic films lost 31-37% of their mass. Leaves of Nothofagus pumilio lost 61-64% of their mass under the same conditions. For both leaf species, differences in mass losses among treatments were not statistically significant. Sporulation rates were significantly lower in the SHADE treatment. Fungal biomass accounted for 6.2 to 7.1% of leaf mass, without significant differences among treatments.In the laboratory, leaf discs of A. glutinosa colonized by single species of aquatic hyphomycetes (Articulospora tetracladia, Flagellospora curta or Lunulospora curvula) and exposed to or protected from UVR did not differ in mass loss and sporulation rates. Pure cultures of two fungal species grew at the same rates when exposed to light (PAR and PAR + UVR) or to the SHADE. In summary, we found no evidences that current high levels of UV radiation affect litter decomposition mediated by aquatic hyphomycetes. IntroductionLeaf litter decomposition is a fundamental ecosystem process which is influenced by a complex interaction of environmental factors (i.e., current velocity, water chemistry) and intrinsic litter chemical and physical properties (e.g., lignin, nitrogen, polyphenolic content, and leaf toughness) (e.g., MALTBY, 1996 ;GULIS et al., 2006) . One of the environmental factors which has received less attention is sunlight incidence. Research on terrestrial litter decomposition has demonstrated that fungi are negatively affected by UVR (NEWSHAM et al., 1997 ;SEARLES et al., 2001 ) resulting in reduced leaf litter mass loss (PANCOTTO et al., 2003) . Enhanced UV-B radiation affect biological processes, mainly by damaging DNA (ROUS-SEAUX et al., 1999 ), further affecting growth, reproduction (BANCROFT et al., 2007 ) and also ecosystem processes like those involved in material and energy cycling (PAUL and GWYNN-JONES, 2003

Photoactive titanium dioxide nanoparticles modify heterotrophic microbial functioning

“…3c). The stimulation of microbial leaf decomposition even in the absence of nTiO 2 is contrary to an earlier study (Díaz Villanueva et al 2005) but may be explained by UV-induced photodegradation of lignin to more easily assimilable or leachable organic carbon (King et al 2012) as suggested in terrestrial systems (Rozema et al 1997). As changes in the stoichiometry of the leaf litter are rather marginal (Table 1), we are not able to provide data supporting this mechanism.…”

Microbial race to colonise leaf litter in a littoral‐lake environment and its relation to nutrient dynamics

“…Some colonisation experiments conducted in light and dark conditions showed that, while primary producers obviously grew better in light, fungi grew better in dark conditions (Albariño et al, 2008; Halvorson et al, 2018). In contrast, the negative effect of light on fungal growth was rejected in a study using fungal cultures, without primary producers, with PAR, UV + PAR, and dark conditions, where neither leaf mass loss, sporulation rates, nor fungal growth were affected by light treatment (Diaz‐Villanueva et al, 2010). These results pointed to the idea of negative interactions between autotrophs and fungi.…”