Heterogeneity in the dissolved organic matter features as expression of precipitation gradient in seasonal wetlands in austral forest of Patagonia

Abstract

Seasonal wetlands are complex ecosystems highly dependent on climatic variation dueto their small size and shallowness. Wetlands are carbon (C) reservoirs and the major fraction of the C is in the dissolved phase as part of the dissolved organic matter (DOM). Due to limited information about the characteristics of the DOM regarding source, molecular size/weight and diagenetic state, we aimed to performed an optical DOM characterization of 12 temporary wetlands located in the Argentinean Patagonia. As a result, we found that wetlands located in the austral forest have variable amount of dissolved organic carbon (DOC), ranging from 26.04to 0.9 mg L−1 in a strong longitudinal gradient from west to east, respectively. The proxy for terrestrial input (a350:DOC) showed high values suggesting an allochthonous origin of the DOM. The DOM molecular size ( S275–275) showed that most of the wetlands were characterized by high molecular size/weight DOM. A multivariate analysis (RDA) ordinated the wetlands according to their longitudinal position, in which samples collected at west were characterized by high aromaticity and humification, and low recently produced DOM (low BIX). Meanwhile, at eastern side wetlands are characterized by low DOC, low humic DOM components but increasing values of recently produce DOM (high BIX). This study contributes to understand the interaction between terrestrial and aquatic systems in a pristine region which is increasingly impacted by global climate change.