skip to main content

Title: Mimicry of emergent traits amplifies coastal restoration success
Abstract Restoration is becoming a vital tool to counteract coastal ecosystem degradation. Modifying transplant designs of habitat-forming organisms from dispersed to clumped can amplify coastal restoration yields as it generates self-facilitation from emergent traits, i.e. traits not expressed by individuals or small clones, but that emerge in clumped individuals or large clones. Here, we advance restoration science by mimicking key emergent traits that locally suppress physical stress using biodegradable establishment structures. Experiments across (sub)tropical and temperate seagrass and salt marsh systems demonstrate greatly enhanced yields when individuals are transplanted within structures mimicking emergent traits that suppress waves or sediment mobility. Specifically, belowground mimics of dense root mats most facilitate seagrasses via sediment stabilization, while mimics of aboveground plant structures most facilitate marsh grasses by reducing stem movement. Mimicking key emergent traits may allow upscaling of restoration in many ecosystems that depend on self-facilitation for persistence, by constraining biological material requirements and implementation costs.
Authors:
; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; more » ; ; « less
Award ID(s):
1832178
Publication Date:
NSF-PAR ID:
10312750
Journal Name:
Nature Communications
Volume:
11
Issue:
1
ISSN:
2041-1723
Sponsoring Org:
National Science Foundation
More Like this
  1. Coastal salt marshes are distributed widely across the globe and are considered essential habitat for many fish and crustacean species. Yet, the literature on fishery support by salt marshes has largely been based on a few geographically distinct model systems, and as a result, inadequately captures the hierarchical nature of salt marsh pattern, process, and variation across space and time. A better understanding of geographic variation and drivers of commonalities and differences across salt marsh systems is essential to informing future management practices. Here, we address the key drivers of geographic variation in salt marshes: hydroperiod, seascape configuration, geomorphology, climatic region, sediment supply and riverine input, salinity, vegetation composition, and human activities. Future efforts to manage, conserve, and restore these habitats will require consideration of how environmental drivers within marshes affect the overall structure and subsequent function for fisheries species. We propose a future research agenda that provides both the consistent collection and reporting of sources of variation in small-scale studies and collaborative networks running parallel studies across large scales and geographically distinct locations to provide analogous information for data poor locations. These comparisons are needed to identify and prioritize restoration or conservation efforts, identify sources of variation among regions,more »and best manage fisheries and food resources across the globe. Introduction Understanding the drivers of geographic variation in the condition and composition of habitats is crucial to our capacity to generalize management plans across space and time and to clarify and perhaps challenge assumptions of functional equivalence among sites. Broadly defined wetland types such as salt marshes are often assumed to provide similar functions throughout their global range, such as providing nursery habitat for fishery species. However, a growing body of evidence suggests substantial geographic variation in the functioning of salt marsh and other coastal ecosystems (Bradley et al. 2020; Whalen et al. 2020). Variation in ecological patterns and processes within habitat types can alter community structure and dynamics. Local-scale patterns and processes (e.g., patch [10s of meters], local [100s of meters]) can be influenced by processes that occur at larger spatial scales (e.g., regional [kms], global), thereby causing geographic differences in the function and ecosystem service delivery of a given habitat type. Salt marshes (which include vegetated platform, interconnected tidal creeks, fringing mudflats, ponds, and pools) are widely distributed (Fig. 1) and function as valuable nursery habitats by providing key resources for many estuarine species that transition to marine or aquatic habitats as adults (Beck et al. 2001; Minello et al. 2003; Sheaves et al. 2015). However, factors that underlie variability in the delivery of ecological functions are still inadequately understood. Previous studies have explored geographic variation in the function of salt marshes for fish and mobile crustaceans (“nekton”; e.g., Minello et al. 2012, Baker et al. 2013). However, field studies that compare multiple sites across a geographical gradient are typically limited in duration and scale. In addition, the explanatory variables (e.g., elevation, flooding duration, plant structure) collected by smaller scale studies are often inconsistent and therefore limit generalizations across sites.« less
  2. Foundation species traits that structure communities are rarely experimentally examined; thus, a predictive understanding of their functions lags behind patterns of observed species associations. Red mangrove Rhizophora mangle roots form complex living habitats that support diverse epibiont communities, making them a model system for testing links between variation in foundation species traits and associated biodiversity. Here, we compared epibiont community composition between living and non-living mangrove roots, as well as root mimics, to test how foundation species traits affect community structure. We also quantified the community structure of associated mobile invertebrates to examine their relationship with secondary foundation species (e.g. sponges, bivalves) that grow on the roots. After 14 mo of colonization and succession, substrate composition (i.e. mangrove, wood, PVC) had significant effects on community composition, richness, and abundance of sessile epibionts and mobile invertebrates. Non-living mangrove roots were 5 times more likely to deteriorate, and consequently had the lowest epibiont richness and abundance. We found strong positive relationships between mobile invertebrate richness and the abundance, measured as biomass, and richness of sponges and bivalves, suggesting that variation among roots in secondary foundation species play an important role in mediating mobile invertebrate community composition. This study highlights the functional rolemore »of habitat structure and how rapidly that function can be lost without biogenic maintenance. Our results indicate the importance of facilitation cascades in fostering diverse mobile invertebrate communities and highlight both advantages and limitations in using artificial structures in restoration programs.« less
  3. Accelerated sea-level rise poses a significant threat to coastal habitats, such as salt marshes, which provide critical ecosystem services. Persistence of salt marshes with rising sea levels relies, in part, on vertical accretion. Ecogeomorphic models emphasize the role of plant production in vertical accretion via sediment trapping and belowground organic matter contribution. Thus, changes in plant production can influence saltmarsh persistence with sea-level rise. However, models of marsh accretion do not consider animal-mediated changes in plant production. We tested how 2 marsh crabs, Minuca pugnax and Sesarma reticulatum , which have contrasting effects (facilitation vs. herbivory) on Spartina alterniflora production, may indirectly influence sediment deposition and belowground production, through observational surveys and field manipulation. Minuca facilitated Spartina biomass in some marshes, but not sediment deposition, and had no effect on belowground organic matter contribution, suggesting that in isolation, Minuca has little indirect impact on saltmarsh geomorphic processes. Sesarma reduced Spartina biomass; however, sediment deposition increased, contrary to ecogeomorphic models, likely due to sediment resuspension by Minuca . When Minuca and Sesarma co-occur, the effect on Spartina production and sediment deposition depended on the amount of grazing. When Sesarma grazing is low, Minuca facilitates Spartina growth and mitigates the effect ofmore »grazing. However, when Sesarma grazing is high and vegetation is removed, Minuca can resuspend sediment through bioturbation, suggesting the net effect of these species may depend on their relative abundance. This study demonstrates that the effects of plant-animal interactions on marsh resilience against sea-level rise are context dependent.« less
  4. Oyster populations within the coastal bays of Virginia have greatly declined, mainly due to overharvesting and disease, and past restoration efforts have largely focused on increasing their populations. Current restoration goals have now expanded to simultaneously procure the wider ecosystem services oysters can offer, including shoreline protection and ecosystem diversification. However, tradeoffs exist in designing artificial reefs because it is unlikely one design will optimize all services. This study compares the services provided by reef designs varying in elevation and width located adjacent to an intertidal marsh within a coastal bay of VA, USA. We quantified wave attenuation to determine potential coastal protection of the adjacent marsh, and changes to sediment composition and infaunal communities before and after reef construction for 3 years. After construction, we also quantified oyster size and population density to compare high and low elevation reef designs. High elevation reefs were more effective at attenuating waves and fostering oyster growth compared to low elevation reefs. Oysters atop high elevation reefs were on average approximately twice as dense and 20% larger than those on low elevation designs. Reef width had a minimal effect on oyster population density; densities on high and low reefs were similar for designsmore »with one or three rows. The presence of oyster reefs also increased infaunal diversity and sediment organic matter. Our results indicate that artificial reef design can differentially affect the services provided through restoration, and elevation is especially important to consider when designing for oyster population enhancement and coastal protection.« less
  5. Louisiana’s Comprehensive Master Plan for a Sustainable Coast is the state of Louisiana’s ambitious response to its continuing land loss crisis. Coastal restoration enjoys universal approval as a political issue in the state; however, controversy exists over a specific project type that seeks to divert sediment from the Mississippi River into surrounding marsh. While the State argues that sediment diversions are critical for land building, widespread concerns persist that changes to the estuary will generate economic hardship for coastal communities. This study investigates the structural challenges that diversion opponents have faced in their effort to mount effective resistance to the State’s sediment diversion projects. The study uses Lukes’ radical perspective of power to explore the ways in which the institutional configuration in Louisiana’s coastal zone produces an insular bureaucratic coalition that limits political opportunity for excluded groups to affect the coastal planning process. This article argues that this coalition, and the State and the energy industry in particular, has been able to leverage non-decision power and ideology to inhibit mobilization against the diversion component of the coastal master plan.