Seascape Configuration Influences the Community Structure of Marsh Nekton

Abstract

Around the globe, salt marsh ecosystems are rapidly changing, leading to alterations in both the amount, and configuration of marsh habitats. Sea level rise is a key driver of salt marsh change and is decreasing marsh habitat cover while increasing fragmentation. Such changes in seascape structure are expected to alter the ecological communities associated with marsh habitats. The influence of seascape structure on marsh nekton community structure is not well characterized, especially in coastal areas of the Gulf of Mexico, such as Louisiana (USA). Louisiana is losing marsh habitat at an unprecedented rate, and the resulting habitat loss and fragmentation provides a unique study system to investigate how marsh seascape structure impacts the nekton community. In this study, seascape structure was characterized at the 1- and 5-km scale at sampling points across several coastal basins to test marsh seascape structure effects on nekton community characteristics. Nekton communities were sampled using seine nets across coastal Louisiana in 2007. Total nekton community structure was found to be spatially driven. Both nekton species richness and nekton abundance were influenced by the shape of marsh patches and proportion of landscape marsh measured at either scale. While species richness differed only between some of the basins, each basin was found to have a statistically distinct community structure. Marsh shape influenced brown and white shrimp size. However, the response direction was found to be species specific, with brown shrimp size increasing in marshes with more complex shape while white shrimp size decreased. This study demonstrates that both environmental drivers and seascape structure play important roles in structuring marsh nekton communities, and that these responses can be species-specific. In order to project complex interactions between coastal land loss and their communities, a holistic framework of community structure, environmental drivers, and seascape characteristics is recommended.