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Incorporation of Faunal Engineers into Models of Salt Marsh Accretion

Dr. Sinead Crotty, University of Florida

Vegetated coastal ecosystems provide critical ecosystem services to coastal communities, but their ability to withstand increasing rates of sea-level rise is unclear. While modeling efforts have expanded in their complexity and predictive power, no current efforts include faunal engineering effects on accretion processes. To address this gap, we used southeastern US salt marshes as a model system, utilizing a combination of experiments, landscape measurements, predation assays, and aerial imagery analyses to assess the relative importance of two fauna engineer functional groups: 1) the biodepositing bivalve, the Atlantic ribbed mussel (Geukensia demissa), and 2) the bioturbating marsh grazer, the purple marsh crab (Sesarma reticulatum). First, we show that the spatial patterning of both groups of faunal engineers is highly predictable across regional, landscape, and local scales based on underlying landform geomorphology. We then utilize further large-scale experiments and landscape measurements to quantify the relative contribution of these engineering organisms to accretion processes. We find that despite both functional groups occupying only ~1% of marsh platforms in the region, both exhibit keystone effects on ecosystem function; mussels contribute between 7 and 18% of landscape marsh deposition, levels that are predictably dictated by season, tide, and geomorphology. In contrast, marsh crab grazing fronts—which are increasing in response to sea level rise—strongly reduce secondary productivity of adjacent marsh platforms, reducing mussel survivorship where the two groups overlap. Therefore, as sea levels continue to rise and vegetated coastal ecosystems are increasingly submerged, the role of engineering fauna and the novel interactions that arise among these organisms are likely to play a dynamic and critical role in the system response to sea-level rise—a result that should be incorporated into ecogeomorphic models of accretion.


Coastal Resilience: Exploring the Impacts of Management Decisions, Hazards, and Climate Change on Developed Shorelines

Dr. Devon Eulie, University of North Carolina - Wilmington

Coastal resilience is a complex topic that requires a multifaceted approach. I seek to not only understand the impact of human activities and natural events (such as global climate change) on coastal environments and resources, but also work directly with coastal communities to ensure they have the data and tools necessary to build resilience in a sustainable way. My research program focuses broadly on coastal resilience, encompassing themes such as coastal hazards, ecosystem restoration, coastal management, and watershed planning. My research also encompasses multiple spatial and temporal scales. Specifically, my research has ranged from parcel level geomorphological studies to coast-wide spatial analysis, and single event, post-hurricane monitoring response to long-term 80-year shoreline change analysis. My research has a current geographic focus area of the North Carolina coastal zone; however, the challenges faced in North Carolina are in many ways universal to developed shorelines everywhere. I approach these studies with a combination of innovative technology, such as UAS and RTK-GPS, and geospatial modeling.



Surging seas and shifting sands:  Forecasting coastal hazards for a society at risk

Dr. Joseph Long, University of North Carolina - Wilmington 

Drivers of coastal change vary spatially and temporally and can be hydrodynamic (e.g., waves, tides, surge, sea level-rise), geomorphic (e.g., sediment type, nearshore geology), and anthropogenic (e.g., beach nourishments, structures impeding sediment delivery). My research focuses on using a range of numerical models, data types, and assimilation techniques to understand, quantify, and predict the vulnerability of U.S. coastlines to these various drivers. This talk summarizes a range of research and decision support applications ranging from the use of high-fidelity numerical models to evaluate the sustainability of potential barrier island restoration templates to efficient statistical approaches that can be applied nationwide in a consistent framework to predict future shoreline change. Each of these projects leverages a combination of elevation data, satellite imagery, and vegetation characteristics to assess current and future vulnerability of coastal environments and the infrastructure and ecosystem services they support.


Ongoing nutrient enrichment shifts microbial community patterns and processes in a coastal plain wetland

Dr. Ariane Peralta, East Carolina University

Over the last century, increasing fertilizer use and burning of fossil fuels have increased global nitrogen and phosphorus deposition rates. This atmospheric fertilization effect can be particularly disruptive to biogeochemical cycling in historically low nutrient ecosystems. Investigating plant-soil-microbial interactions and their influence on microbial metabolism is essential for predicting microbial contributions to carbon cycling as atmospheric deposition persists. In this study, we use a combination of molecular and culture-based approaches to examine long-term nutrient enrichment effects on plant-soil-microbial interactions in a nutrient-limited wetland. Since 2003, a factorial experiment located in the eastern North Carolina coastal plain has been maintained to study effects of nutrient addition (N-P-K fertilizer), disturbance (mowing), and their interaction on wetland plant and microbial community structure and function. Results reveal that bacterial taxonomic diversity (based on 16S rRNA amplicon sequencing) in both bulk soils and plant rhizospheres are higher in fertilized soils than ambient soils. We detected higher metabolic rates and substrate use diversity (based on phenotypic microarray assays, litter decomposition) in fertilized compared to ambient conditions. Our ongoing work suggests that nutrient enrichment influences plant-soil-microbial relationships in ways that could reduce carbon storage potential of coastal plain wetlands.


Modex and landsurface processes: Thoughts on matching models, scales, and process-based observations

 Dr. Joel Rowland, Los Alamos National Laboratory

 A fundamental challenge for Modex-directed science is the common mis-match between scale, complexity, and motivations of observational and modeling efforts. This mis-match is particularly true when trying to connect landscape dynamics with Earth System Models. Fundamentally, however, a Modex framework, with a strong emphasis on making observations and developing models that have transferability from one setting to many, provides an opportunity to both challenge the depth of our knowledge and force the need for hypotheses driven science. On projects focused, arctic river and floodplain dynamics, permafrost hillslopes, and coastal change modeling, we have attempted to develop observational programs, both field and remotely sensed, parameterizations for existing models, and prioritize new model developments. In all of these instances, there is an iterative and dynamic interaction between collecting observations to parameterize and test models, and the use of poorly constrained models to test broad hypotheses and guide observational efforts. In many cases, this process has led to a recognition that fundamental process understanding that may be most intellectually rewarding is often not needed for some modeling efforts. At the same time, however, the use of a multi-scale modeling approaches has highlighted opportunities for making detailed process-based observations to inform the transfer of understanding across large spatial and temporal scales.

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