Ecological Indicators 19 (2012) 89–97 Contents lists available at ScienceDirect Ecological Indicators jo ur nal homep age: www.elsevier.com/locate/ecolind Performance of biotic indices in naturally stressed estuarine environments on the Southwestern Atlantic coast (Uruguay): A multiple scale approach Pablo Muniz a,∗ , Marisa Hutton a , Noelia Kandratavicius a , Andrea Lanfranconi a , Ernesto Brugnoli a , Natalia Venturini a , Luis Giménez b a Oceanografía y Ecología Marina, Facultad de Ciencias, UdelaR, Montevideo 11400, Uruguay b School of Ocean Sciences, University of Wales, Bangor, Menai Bridge, Anglesey LL59 5AB, UK a r t i c l e i n f o Keywords: Estuaries Coastal lagoons Hierarchical nested sampling design Spatio-temporal variation Benthic fauna a b s t r a c t Biotic indices based on benthic communities have become an important tool in the assessment and monitoring of marine pollution. These communities vary at several spatial and temporal scales giving rise to scale-dependent patterns of distribution, being of particular importance because results from the application of ecological indices, and the subsequent classification of communities, could reflect these variations at several scales. We test some of the most widely applied indices for the evaluation of coastal benthic communities, using a hierarchical spatio-temporal sampling design, within two sets of estuarine habitats in the Atlantic coastal zone of Uruguay. Results showed that ecological indices can vary at different spatial scales, with important variation at small scales. So, independently from the used index, an appropriate sampling design should be taken into account considering different scales (both spatial and temporal). At some of the scales studied, indices appear to reflect natural variations in disturbance through currents rather than variation in anthropogenic effects. At the large scale, variation is low consistent with a preliminary classification of sites according to the putative levels of human activity. The low level of similarity between all indices could be denoting some degree of inconsistency in the assignment of the categories to an ecological status. © 2011 Elsevier Ltd. All rights reserved. 1. Introduction The use of biotic indices has become an important tool in the assessment and monitoring of the biological effects of marine pol- lution. Various studies have demonstrated that benthic organisms are useful indicators of environmental status, as they respond pre- dictably to several types of natural and anthropogenic disturbances (Grall and Glémarec, 1997; Borja et al., 2000; Gómez-Gesteira and Dauvin, 2000; Simboura and Zenetos, 2002; Rosenberg et al., 2004). Although a number of indices are available for marine/estuarine coastal environments, there is a lack of consensus about which is the most appropriate. A major concern about their applicability is that they ought to respond differently to natural and man-induced changes in communities. Another important issue is that selecting different indices may result in different classifications of ecological status, as shown by several recent papers in this topic (Borja et al., 2007 and references therein). ∗ Corresponding author at: Oceanografía y Ecología Marina, Facultad de Ciencias, Iguá 4225, Montevideo 11400, Uruguay. Tel.: +598 25258618x7150; fax: +598 25258617. E-mail addresses: pmmaciel@fcien.edu.uy, pablo.munizmaciel@gmail.com (P. Muniz). The hydrodynamics at coastal areas can be considered as a source of natural disturbance for soft sediment communities (Levin and DiBacco, 1995; Roth and Wilson, 1998; Hewitt et al., 2003). Sed- iment characteristics are the result of near-bed flow conditions, which influence grain size, sedimentary organic matter content, pore-water chemistry, microbial content and larval supply (Gray and Elliot, 2009). These variables can directly or indirectly influence the benthic species distribution (Gray and Elliot, 2009) therefore influencing, in a general way, community structure and function- ing. Hydrodynamic forces and other factors operate on benthic communities at several spatial and temporal scales giving rise to scale-dependent patterns of distribution (Thrush et al., 1997, 2003; Giménez and Yannicelli, 2000; Ysebaert and Herman, 2002; Giménez et al., 2005, 2006). These are of particular importance because results from the application of ecological indices, and the subsequent classification of communities, could reflect variations in hydrodynamics at several spatial scales. Patterns of variability may be more evident at some scales than others; therefore, evalua- tion of ecological status of natural communities must consider the scale-dependent nature of their structure. Few studies have been done to explore the performance of biotic indices considering the natural spatial and temporal variability of macrobenthic communi- ties (Reiss and Kröncke, 2005; Labrune et al., 2006; Quintino et al., 1470-160X/$ – see front matter © 2011 Elsevier Ltd. All rights reserved. doi:10.1016/j.ecolind.2011.07.022