A review of fish diversity in Mediterranean seagrass habitats, with a focus on functional traits

Abstract

Besides providing key ecosystem services, including improved water quality, coastal protection, and carbon sequestration, seagrasses are highly productive habitat-forming species essential in supporting fish diversity at the global level. In the Mediterranean Sea, seagrasses represent the main component of the sublittoral marine environment hosting a huge number of fish species that use this habitat for reproduction, foraging and/or refuge from predation. However, a complete synthesis of fish species observed in different seagrass habitats is still lacking at the whole Mediterranean basin scale, so hindering a thorough understanding of the main mechanisms involved in determining fish diversity patterns. We performed a systematic review by implementing a semi-automated, threshold-based filtering pipeline that allowed building up a dataset concerning all fish species reported in native Mediterranean seagrasses, including specific functional traits known to be involved with the potential use of seagrasses by fish. These data allowed to carry on a narrative synthesis on fish diversity in seagrass habitats, providing support to several assumptions repeatedly stated in literature but so far sustained mainly by local and fragmented data. Our findings suggested the onset of a general pattern in the occurrence of species, mostly based on life history and driven by body size and feeding habits. We evidenced unexpected knowledge gaps on the role of habitat heterogeneity and fish life stages in determining the presence and the potential use of seagrasses by species. In depth studies are therefore needed to better understand the mechanisms behind the structuring of fish communities, fundamental for the maintenance of marine biodiversity.