Habitat Characteristics and Plant Community Dynamics Impact the Diversity, Composition, and Co-occurrence of Sediment Fungal Communities

Habitat edge effects can have profound impacts on biodiversity throughout terrestrial and aquatic biomes. Yet, few studies have examined how habitat edge effects impact the spatial patterning of sediment properties and microbial communities, especially in coastal ecosystems. Coastal salt marshes throughout the world are being transformed by sea level rise; high-marsh, flood-intolerant species, such as Spartina patens, are being fragmented and replaced by low-marsh, flood-tolerant species, such as Spartina alterniflora. The consequences of these habitat transformations on fungal communities remain unclear. Thus, we sought to identify how habitat edge effects, alongside changing plant community dynamics, impact the spatial patterning of fungal communities associated with ubiquitous Spartina species. We analyzed 26 Spartina patens patches: 13 pure monocultures and 13 mixed patches with Spartina alterniflora infiltration. We measured patch characteristics, plant characteristics, sediment physicochemical properties, and sediment fungal communities. We found that habitat edge effects structured sediment and plant properties in both pure and mixed patches. However, habitat edge effects only structured fungal community composition in mixed patches, counter to expectations. These results indicate that changing plant community dynamics driven by sea level rise can exacerbate habitat edge effects in coastal ecosystems. Least discriminant analysis and co-occurrence networks further revealed unique taxa and network structures between pure and mixed patches and between interiors and edges. In sum, we found that habitat transformation of coastal salt marshes driven by global change impacts the spatial dynamics of sediment and fungal properties.