La comunità macrozoobentonica come strumento per la valutazione dello stato di qualità ecologico in ambienti di transizione: il caso della laguna di Santa Gilla

Transitional habitats are vulnerable ecosystems, affected by strong and unpredictable environmental parameters and exposed to several threats, both natural and anthropic, that can deeply interfere with the biological components critical to their functionality (Lardicci et al., 1993; Fraschetti, 1996; Giangrande & Mistri et al., 2000; Lardicci et al., 2001,). The conservation and management of these habitats require an integrated study of three aspects: chemical, physical and biological (Gibson et al., 2000). Recent directives, specifically Water Framework Directive 60/2000/EC and Marine Strategy Framework Directive 56/2008/EC, suggest that biological elements are essential tools to evaluate the quality of coastal and transitional ecosystems. In particular, the macrozoobenthic component is often employed in transitional environmental programs (Blanchet et al., 2008). The location analyzed in this study is one of the most important wetlands in Sardinia. Despite this, there is no complete and recent information about the benthic community. The main aim of this study is to characterize the Santa Gilla lagoon, studying some abiotic aspects (granulometry, mineralogy, heavy metals and organic matter in sediments, and salinity, pH, dissolved oxygen and temperature of the water column) and providing information about the macrozoobenthic community in relation to spatial-temporal variations, creating the research foundation for the development of an appropriate resource management and conservation strategy. A total of 16910 organisms were found, belonging to 114 different taxa. The distribution of these organisms in relation to the abiotic parameters was studied. Multivariate analysis highlighted two main groups, originating from distinct areas of the lagoon and influenced by different factors. However, it is difficult to determine which variable most strongly influences the distribution of the community. Indeed, benthic organisms are expected to respond to a more complex set of environmental factors related to the water column, sediment, interstitial water, and interface layer (e.g. Maurer et al., 1985; Whiteman et al., 1996). Different biotic indices were applied and their effectiveness was evaluated. The results were varied, but all measurement indices concluded that best ecological quality measured was in close proximity to the sea. Through this project, important information necessary for future integrated ecosystem management was gathered. Undoubtedly, the analysis of the macrozoobenthic community is a prerequisite for the evaluation and management of ecosystems in a sustainable and appropriate manner (Ludovisi et al., 2013). Thus, this study constitutes the starting point for future quality status assessments, as well as the basis for subsequent analysis and monitoring.