Disentangling the interaction between dissolved organic matter quality and bacterial degradation across Andean North-Patagonian freshwater networks

BASTIDAS NAVARRO M.; E. BALSEIRO; N. MARTYNIUK; B. MODENUTTI

Valparaíso, Chile

Congreso; ISME-LA; 2019

ISME

Microbial degradation is one of the most important pathway by which dissolved organic matter (DOM) influence aquatic metabolism. As important as the amount of C-consumed by bacteria is the residual C-pool (molecules that become resistant to degradation and accumulate in the environments). Here we addressed how DOM composition and nutrients concentration (C, N, and P) affect C-consumption in Andean North-Patagonian networks, and the accumulation of C as residual. We combined field sampling of different aquatic ecosystems (deep, shallow, high altitude lakes, rivers, and wetlands) with DOM-lability experiments. We also analyzed different DOM sources (soil, benthic algae, macrophytes, senescent leaves leachates of different tree species) in order to track the probable origin of the DOM bulk. We observed a large variation in nutrient concentration across the different systems, being wetlands those with the widest range, and with the highest values. DOM characterization was performed by fluorescence excitation-emission matrices and analyzed with PARAFAC model. We identified 4 fluorescent components in DOM, three of which (C1, C3, and C4) had fluorescence emissions that resembled terrigenous-humic substances, and were particularly present in Nothofagus spp leachates. C2 showed fluorescence emissions similar to tryptophan (protein-like compound). Lability experiments showed that the proportion of residual C increased with the increase of dissolved N and the terrigenous C1, and decrease with increasing dissolved P concentration. High C1 was also related with low C-specific consumption. Our results showed that the highest inputs of DOM of terrigenous origin, associated also with higher N concentrations, favor DOM accumulation in the environments.