Marine fauna sort at fine resolution in an ecotone of shifting wetland foundation species

Abstract

Climate-driven global change is shifting the distribution and abundance of foundation species that form the base of ecosystems. The corresponding responses of inhabitant species to shifts in habitat-forming species are poorly understood, however we expect community responses to depend on how species perceive habitat patches and sort among them, particularly along range edges. We used the poleward shift of a mangrove-marsh ecotone to evaluate sorting of marine macrofauna (small fish and decapod crustaceans) among vegetation patches at a series of nested scales. Within the mangrove-marsh ecotone, we deployed retrievable panels of artificial vegetation structures mimicking a marsh grass and two mangrove species in patches dominated by each of these three foundation species. Over six months, we observed macrofaunal sorting by physical structure, isolated on panels, and by patch type, which included stand-level attributes such as production, shading, and chemical cues. We found multiscale partitioning of macrofaunal community composition by site (kilometer scale), vegetation type, and patch type with stand attributes (meters), and physical structure (centimeters). Differences in community composition between vegetation types at each scale indicated that mangroves and marsh grass differ as habitat for marine fauna and that wetland inhabitants can distinguish and sort among fine-grain habitat patches that co-occur within the ecotone. Such differences suggest that shifts in wetland vegetation are consequential for the protection and management of coastal populations. Studies that determine which habitat attributes shape inhabitant fauna associations can help reveal not just the spatial grain at which inhabitants associate with emerging frontier habitat but also how the redistribution of foundation species shapes the pace and resolution of broader community change.

Evidence for the genetic similarity rule at an expanding mangrove range limit

“…We documented a correlation between mangrove host-tree genetics and fungal community differences, but does this relationship generate variation in stress tolerance among mangrove hosts? If so, this insight could broaden the current discussion of how a shift from salt marsh to mangrove dominance may shape these coastal communities (e.g., Kelleway et al, 2017;Johnston and Gruner, 2018;Smith et al, 2019;Armitage et al, 2020) by including mangrove intraspecific variation as a factor that could influence population resilience at these high-stress range limits.…”

The impacts of mangrove range expansion on wetland ecosystem services in the southeastern United States: Current understanding, knowledge gaps, and emerging research needs

“…and fish were more abundant in marshes bordered by mangroves (Smee et al, 2017). Similarly, macrofaunal communities differed in marsh versus mangrove-dominated vegetation along the Atlantic coast of Florida, due to the influence of fine-scale plant structural differences and stand-level habitat attributes (Johnston & Gruner, 2018). Along the Atlantic coast, studies have noted differences in detrital-based epifaunal communities (Smith et al, 2019) Beyond just the direct effects on animals, mangrove expansion can also affect microbial (Barreto et al, 2018) and rhizosphere communities (Chen et al, 2020), which can affect abiotic conditions, biotic interactions, and biogeochemical cycling.…”

“…were less abundant in marshes bordered by mangroves than in marshes without mangroves, whereas mud crabs (Xanthidae/Panopeidae) and fish were more abundant in marshes bordered by mangroves (Smee et al, 2017). Similarly, macrofaunal communities differed in marsh versus mangrove‐dominated vegetation along the Atlantic coast of Florida, due to the influence of fine‐scale plant structural differences and stand‐level habitat attributes (Johnston & Gruner, 2018). Along the Atlantic coast, studies have noted differences in detrital‐based epifaunal communities (Smith et al, 2019) and subtidal nekton communities (Kimball & Eash‐Loucks, 2021) associated with mangroves compared to marshes.…”