Ecological Modelling 222 (2011) 91–104 Contents lists available at ScienceDirect Ecological Modelling journal homepage: www.elsevier.com/locate/ecolmodel Development of a mechanistic model (ERIMO-I) for analyzing the temporal dynamics of the benthic community of an intermittent Mediterranean stream Nele Schuwirth a,∗ , Vicenc ¸ Acu˜ na a,b , Peter Reichert a a Eawag: Swiss Federal Institute of Aquatic Science and Technology, Ueberlandstrasse 133, CH-8600 Dübendorf, Switzerland b ICRA: Catalan Institute for Water Research, Parc Científic i Tecnològic de la Universitat de Girona, E-17071 Girona, Spain article info Article history: Received 19 March 2010 Received in revised form 10 September 2010 Accepted 14 September 2010 Available online 8 October 2010 Keywords: Stream ecology Community dynamics Bayesian inference Sensitivity analysis Benthos Invertebrates Periphyton abstract To evaluate the role of the benthic community within headwater stream ecosystems, it is crucial to understand the mechanisms of the processes dominating their turnover rates and temporal dynamics. To analyze the benthic community dynamics of an intermittent Mediterranean stream (Fuirosos, Spain), we developed a mechanistic model that describes the most important ecosystem components (five func- tional feeding groups of invertebrates, periphyton, and benthic organic matter) under consideration of important transformation processes. The model is an extension of that developed for application to the prealpine River Sihl (Switzerland). A combination of prior knowledge from the literature and information from field observations within a Bayesian framework is used to constrain plausible ranges of the esti- mated model parameters and to evaluate the uncertainty of the model outcome. The Bayesian inference resulted in a realistic description of most of the main features of the system, offered insights into the degree of information the data contains about model parameters, and also made it possible to quantify the dependence structure of the parameter estimates. Local and global sensitivity analyses revealed that rate parameters for growth and death of invertebrate functional feeding groups are most influential on the model results and additional information on these parameters would be most helpful to reduce output uncertainty. The study clearly points out the importance of organic matter dynamics, as allochthonous organic matter is the main energy source in this Mediterranean headwater stream. Hydrological distur- bances of the system such as droughts and floods lead to complex colonization patterns which would require additional data to support a more detailed description by an extended model. Furthermore, the study shows that it is possible to deal with a complex ecological model with eight state variables and more than 60 parameters in a Bayesian framework. © 2010 Elsevier B.V. All rights reserved. 1. Introduction Headwater streams typically represent from 60% to 80% of the total stream length within a catchment (Schumm, 1956; Shreve, 1969), and drain 70–80% of the total catchment area (Sidle et al., 2000; Meyer and Wallace, 2001). Headwater streams have a well-recognized role as biodiversity hotspots and as transform- ers of dissolved and particulate materials from terrestrial habitats (Alexander et al., 2000; Bernot and Dodds, 2005). Their small size makes them particularly responsive to natural and anthropogenic disturbances such as debris flows, changes in vegetative cover, changes in sediment inputs, and changes in organic matter inputs (Benda et al., 2005). The predominance of headwater streams in the river network and their high sensitivity to disturbances makes them of increasing interest to scientists and resource managers (Whiting and Bradley, 1993; Gomi et al., 2002). ∗ Corresponding author. Tel.: +41 44 8235528. E-mail address: nele.schuwirth@eawag.ch (N. Schuwirth). The benthic community of headwater streams is an important part of their food web, which contributes directly to transformation of nutrients and organic matter in the river. Within the benthic community, invertebrates play an important role in nutrient and organic matter turnover because of their consumption of benthic biofilms, organic particles in the sediment, and suspended particles (Cuffney et al., 1990; Wallace and Webster, 1996). For the evalua- tion of the significance of the benthic community within the stream ecosystem, it is crucial to understand the mechanisms of the pro- cesses dominating their substance turnover rates and dynamics. To evaluate and improve our understanding of these processes, we develop a mechanistic model that describes the temporal dynamics of the biomass of the most important functional benthic organism groups under consideration of important transformation processes. This is a different approach to other studies which try to describe the number of macroinvertebrate families or biotic indices (e.g. Canobbio et al., 2009; Poquet et al., 2009). Mechanistic models describe the underlying functional mechanisms of the processes of interest. However, such models tend to use empirical relation- ships to parameterize these processes. With the help of such a 0304-3800/$ – see front matter © 2010 Elsevier B.V. All rights reserved. doi:10.1016/j.ecolmodel.2010.09.013