Saprobity: a unified view of benthic succession models for coastal lagoons

We briefly review and expand upon classic conceptual models describing the succession of benthic communities along a gradient of organic matter (OM) enrichment developed for freshwater (the Saprobity System), coastal marine (the Pearson-Rosenberg [P-R] model) and lagoon (the Gu,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.