OPINION PAPER Saprobity: a unified view of benthic succession models for coastal lagoons Davide Tagliapietra • Marco Sigovini • Paolo Magni Received: 17 December 2010 / Revised: 20 December 2011 / Accepted: 15 January 2012 / Published online: 2 February 2012 Ó Springer Science+Business Media B.V. 2012 Abstract We briefly review and expand upon classic conceptual models describing the succession of ben- thic communities along a gradient of organic matter (OM) enrichment developed for freshwater (the Sap- robity System), coastal marine (the Pearson–Rosen- berg [P–R] model) and lagoon (the Gue ´lorget– Perthuisot [G–P] model) ecosystems. Differences and similarities between various approaches and models are highlighted and the P–R and G–P models are unified under a single conceptual framework of habitat saprobity in coastal lagoons. We refer to saprobity as the state of an aquatic ecosystem resulting from the input and decomposition of OM and the removal of its catabolites. In addition to other factors, such as salinity, saprobity is viewed as a selection factor for species diversity. The higher the saprobity is, the more impaired the system is, with progressively poorer benthic communities characterized by species that are increasingly tolerant of reducing conditions and toxicity. In coastal lagoons, these processes are strongly driven by hydrodynamics, which govern the land–sea gradient. Based on our review and analysis, we find that saprobity can be a useful descriptor of ecosystem state as determined by OM metabolism, suitable for characterizing the natural conditions of coastal lagoons and assessing their quality. Keywords Saprobity Á Organic matter enrichment Á Macro-invertebrates Á Benthic indicators Á Biotic indices Á Coastal lagoons Introduction Lagoons and estuaries are characterized by composite environmental gradients, involving salinity, seawater renewal, nearshore-offshore distance, nutrients, tur- bidity and sedimentological features (Tagliapietra et al., 2009). The contribution of the different phys- ico-chemical variables depends on the system’s main hydrodynamic energy source (Boyd et al., 1992; Dalrymple et al., 1992; Heap et al., 2001). In estuaries, where riverine inputs are important, the environmental gradient is mainly structured by the flow of fresh water, which generates a salinity gradient. Conversely, in coastal lagoons with more limited fluvial input, the gradient is mainly influenced by seawater renewal. Handling editor: Pierluigi Viaroli D. Tagliapietra Á M. Sigovini Á P. Magni CNR – Consiglio Nazionale delle Ricerche, ISMAR Istituto di Scienze Marine, Arsenale – Tesa 104, Castello 2737/F, 30122 Venezia, Italy P. Magni (&) CNR – Consiglio Nazionale delle Ricerche, IAMC Istituto per l’Ambiente Marino Costiero, Localita ` Sa Mardini, Torregrande, 09170 Oristano, Italy e-mail: paolo.magni@cnr.it 123 Hydrobiologia (2012) 686:15–28 DOI 10.1007/s10750-012-1001-8