Microbial colonization on decomposing litter in a low nutrient lentic environment under different flooded conditions

DIAZ VILLANUEVA, V; CUASSOLO, FLORENCIA

Zagreb

Simposio; 15th Symposium on Aquatic Microbial Ecology; 2017

Institute Ruđer Bo?ković

Plant litter decomposition depends on a wide range of physical, chemical, and biological variables. Colonization by microorganisms represents a fundamental step in this process. Our hypothesis was that the timing of litter entering the water affects decomposition rate, because of differences in the associated biota. To test this hypothesis we compare colonization of autotrophs, bacteria and fungi on leaves of two different plant species during the first months of decomposition under two flooded regimes: completely aquatic vs initially terrestrial. The experiment was carried out in microcosms in the littoral zone of an oligotrophic lake. We measured remaining mass, chlorophyll concentration, bacterial abundance and fungal biomass after 7, 21, 42, 77 and 105 days of experiment and nutrient content. Mass loss was higher in the treatment that was exposed to initial terrestrial conditions. This could be explained by the rapid formation of biofilm on leaves in the water which add biomass to litter. Chlorophyll increase was higher on leaves placed in water from initial time, while chlorophyll increase on leaves exposed to terrestrial conditions, once they were flooded, was slower. Nutrient changes during the process depended on the species and differed between N and P. While P was mostly lost during decomposition, there was a net gain of N. Our results showed that in lentic littoral habitat, litter represents an important supply of substrate to biofilm formation, where autotrophs greatly contribute to total litter biomass, and make decomposition a process that strongly differs from that of lotic environments