Limnetica 35

Scientists have spent decades measuring inputs, storage and breakdown of organic matter in freshwaters and have documented the effects of soil uses, pollution, climate warming or flow regulation on these pivotal ecosystem functions. Large-scale collaborative experiments and meta-analyses have revealed some clear patterns as well as substantial variability in detritus dynamics, and a number of standardized methods have been designed for routine monitoring of organic matter inputs, retention and breakdown in different conditions. Despite the knowledge gathered, scientists have been relatively ineffective at convincing managers of the importance of organic matter dynamics in freshwaters. Here we review the existing information of the role of organic matter as a) an element structuring freshwater habitats, b) a source or sink of nutrients, c) a food resource for heterotrophs, d) a source of pollution, e) a modulator of the fate of pollutants, f) a source of greenhouse gases, g) a potential source of environmental problems, and h) a diagnostic tool for ecosystem functioning. Current knowledge in some of these points is enough to be transferred to management actions, although has seldom been so. Some other points, such as the interactions between organic matter and emerging pollutants, offer interesting research questions.