Dissolved organic matter (DOM) composition exerts a direct control on its degradation and subsequent persistence in aquatic ecosystems. Yet, under certain conditions, DOM degradation patterns cannot be solely explained by its chemical composition, highlighting the relevance of environmental conditions for DOM degradation. Here, we will discuss the results of our experimental assessment on the relative influence of composition vs. environment on DOM degradation based on laboratory bioassays. We inoculated contrasting DOM sources with a standardized bacterial inoculum under distinct conditions mimicking different environmental settings. Our results show that the chemical composition of DOM was more important than the environment in determining its decay patterns and we will discuss the application of the bacterial inoculum as a standard method in this and other studies. The results of a similar experimental contrast in freshwater sediments will also be presented, where the balance between sediment organic matter depositional environments (i.e. composition) and drought exposure (i.e. environment) are at interplay to drive the organic matter compounds present in the sediment. Those experiments, as well as an additional assessment of the literature across freshwaters, soils and the ocean, will lead us to discuss how the relative importance of chemical composition and ecosystem properties diverges across ecosystems or so does our conceptualization on organic matter degradation controls.

Primary Presenter: Núria Catalán, IDAEA-CSIC (ncatalangarcia@gmail.com)

Authors:

Ada Pastor, Universitat de Girona, Girona, Spain  (adapastor@gmail.com)

Carles Borrego, Catalan Institute for Water Research (ICRA), Girona, Spain  (cborrego@icra.cat)

Joan Pere Casas-Ruíz, GRECO, Institute of Aquatic Ecology, University of Girona  (joanpere.casas@udg.edu)

Jeffrey Hawkes, Department of Chemistry, BMC, Uppsala University, Uppsala, Sweden  (jeff.a.hawkes@gmail.com)

Carmen Gutiérrez, Catalan Institute for Water Research (ICRA), Girona, Spain  (cgutierrez@icra.cat)

Daniel vonSchiller, Department of Evolutionary Biology, Ecology and Environmental Sciences, University of Barcelona, Barcelona, Spain  (d.vonschiller@ub.edu)

rafael Marcé, Catalan Institute for Water Research (ICRA), Girona, Spain  (rmarce@icra.cat)