Spatial patterns of seagrasses and salinity regimes interact to structure marine faunal assemblages in a subtropical bay

Anthropogenic disturbances in coastal and marine environments have resulted in the transformation of vegetated benthic habitat spatial patterns, which is thought to influence the distribution, community composition, and behavior of marine fauna. In Biscayne Bay, Florida, USA, freshwater discharges into nearshore areas have resulted in the fragmentation of the spatial patterning of submerged aquatic vegetation (SAV). To understand the ecological consequences of the freshwater-induced SAV seascape fragmentation, fish and crustaceans were sampled using seine nets across seascapes with continuous and highly fragmented SAV spatial configurations and across salinity regimes. Fragmented SAV seascapes supported significantly higher species diversity of fish and crustaceans, especially in areas influenced by freshwater discharges. Also, fragmented seascapes supported a higher abundance of the pink shrimp Farfantepenaeus duorarum and the goby Gobiosoma robustum, and higher biomass of generalist predatory fishes than seascapes with continuous SAV. In contrast, pinfish Lagodon rhomboides was more abundant in seascapes with continuous SAV. Faunal assemblage composition differed between zones of contrasting salinity regimes, and the contribution of species occurrence and abundance to the differentiation of assemblage composition between seascape types was associated with the salinity regimes of the seascapes. Thus, water salinity and spatial properties of SAV seascapes are factors that interact to influence faunal community structure in Biscayne Bay. These findings highlight the importance of understanding how environmental context (e.g. salinity regimes) can modulate the influence of benthic spatial patterning on the abundance and biodiversity of nekton communities.