Distribution modeling of seagrasses in brackish waters of Grado-Marano lagoon (Northern Adriatic Sea) Francesco Boscutti a, * , Ivano Marcorin b , Maurizia Sigura b , Enrico Bressan c , Francesco Tamberlich c , Angelo Vianello a , Valentino Casolo a a Department of Agricultural and Environmental Sciences, Unit of Plant Biology, University of Udine, Via delle Scienze 91, 33100 Udine, Italy b Department of Agricultural and Environmental Sciences, Unit of Rural Buildings and Agro-Forestry Territory, University of Udine, Via delle Scienze 208, 33100 Udine, Italy c Regional Environmental Protection Agency (ARPA) of Friuli Venezia Giulia, Via Cairoli 14, 33057 Palmanova (UD), Italy article info Article history: Received 22 January 2015 Received in revised form 23 May 2015 Accepted 26 July 2015 Available online 29 July 2015 Keywords: Seagrasses Lagoon GLMs Zostera marina Zostera noltii Cymodocea nodosa abstract Seagrasses play an important role in coastal lagoons both as primary producers and ecosystem engineers, thus sustaining biodiversity and ecosystem services. In recent decades, their populations have shown a rapid decrease, mainly due to their vulnerability to environmental degradation. Their ecology was widely investigated in the marine domain whereas the knowledge of their distribution patterns in lagoon waters is still not exhaustive. This study aimed at improving the knowledge of seagrass ecology in such ecosystem. Three seagrass species (i.e. Zostera marina, Zostera noltii and Cymodocea nodosa) occurring in Grado-Marano lagoon (Northern Adriatic Sea -Italy) were studied by examining: (i) the distribution of each taxon, (ii) the main water, and (iii) geomorphological variables, gathered in 466 sample points during field surveys and from literature, respectively. Logistic-Generalized Linear Models (GLMs) were used to develop species distribution models (SDM) of seagrass meadows and single species. The seagrass presence was mainly explained by two clear ecological gradients: (i) sea-inner shoreline and (ii) channel- tidal flats. In particular, seagrasses thrive in areas mostly subjected to marine influence, in both terms of proximity to lagoon inlets and main channels, avoiding areas near major rivers mouths. Species distri- bution models highlighted the crucial role of water salinity and distance from fresh water sources (positively and negatively related, respectively). Zostera marina and Zostera noltii showed similar com- parable effects for most of the ecological predictors, with the exception of water depth (ecological vicariance). Cymodocea nodosa showed a wider ecological variability, with lower goodness of model selection. © 2015 Elsevier Ltd. All rights reserved. 1. Introduction Seagrasses are rhizomatous marine angiosperms widespread in both marine and brackish shallow waters from temperate to trop- ical regions (Short et al., 2007). In these regions, they often act as ecological engineers (Wright and Jones, 2006), forming extensive meadows that are among the most productive ecosystems on Earth (McRoy and McMillan, 1997; Duarte and Chiscano, 1999). Seagrass meadows provide key ecosystem services, including organic carbon production and export, nutrient cycling, sediment stabilization, biodiversity, and trophic transfers to adjacent habitats (Duarte et al., 2005; Duffy, 2006; Orth et al., 2006; Cullen-Unsworth and Unsworth, 2013; Marco-M endez et al., 2015). Although widely distributed, seagrasses have experienced a large-scale decrease in the last decades in most of worldwide populations (Borum et al., 2004; Waycott et al., 2009). These reductions were mainly due to multiple environmental stressors, often attributable to human ac- tivities (e.g. water eutrophication, coastal salinity changes, water turbidity in relationship to sediment management, alien species) (Orth et al., 2006). Seagrass meadows are a pivotal habitat also for transitional water bodies (Aliaume et al., 2007). On the other hand, among transitional water bodies, lagoons are ephemeral and fragile eco- systems, which constitute an important harbor for life (e.g. algae, invertebrates and fish nurseries, migratory birds) (De Wit, 2011; Garrido et al., 2011). Lagoons are shallow aquatic environments * Corresponding author. E-mail address: francesco.boscutti@uniud.it (F. Boscutti). Contents lists available at ScienceDirect Estuarine, Coastal and Shelf Science journal homepage: www.elsevier.com/locate/ecss http://dx.doi.org/10.1016/j.ecss.2015.07.035 0272-7714/© 2015 Elsevier Ltd. All rights reserved. Estuarine, Coastal and Shelf Science 164 (2015) 183e193