Community-level physiological profiles in biofilms from streams differently affected by a volcanic eruption

Volcanic eruptions are catastrophic events that allow testing different impacts on the ecosystems. Inputs of volcanic sediments into stream water may lead to drastic changes in the biota; however, the effects on biofilm functional traits remain poorly understood. This field study aimed to evaluate differences in structural and functional traits in the biofilm of streams differentially affected by the eruption of the Puyehue-Cordón Caulle Volcanic Complex (PCCVC, Chile, 2011). We examined differences in the structure (chlorophyll concentration, bacterial abundance, and biofilm organic matter and phosphorus content) and metabolic capacities (by use of Biolog EcoPlate™) in rock and sand biofilms from six streams with different distances from the volcanic source. Biofilms from streams near the volcano had higher phosphorus content and bacterial abundance. The Biolog EcoPlate™ indicated that there were differences in the use of some particular organic molecules among streams. On one hand, the use of substrate by biofilms from rocks and sand differed only in the non-affected streams. On the other hand, the biofilms of streams nearest the volcano were characterized by the use of galacturonic acid and this higher consumption can be related to the dominance of cyanobacteria. Our results suggest that volcanic sediment inputs, still occurring three years after the eruption, change biofilm communities, leading to physiological differences among streams.