Marshes, mussels, & microbes: Exploring new approaches to sediment addition
With spring just around the corner, Marine Biology graduate student Marjorie Mednikova is preparing to investigate some new beginnings at her field site in Great Bay, New Hampshire. Mednikova’s dissertation research focuses on restoration approaches that can enhance the resilience of salt marsh habitat to climate change. Rapid sea level rise is one of the primary threats to salt marsh habitat today, as increased flooding begins to exceed marshes’ capacity to gain elevation or accrete, resulting in habitat loss. One promising restoration technique that addresses this issue is sediment addition, also known as thin layer placement or TLP. In this approach, sediment is placed on top of deteriorating areas of marsh habitat in an effort to maintain elevation within an optimal range for native plant growth. Over the summer of 2023, Mednikova and many other members of Dr. Gregg Moore’s Coastal Restoration and Resiliency lab worked together to place sediment within experimental plots in Adams Point, Durham. Sediment was added at 14cm depth, consistent with prior research at this site conducted by Dr. Moore and UNH Associate Research Professor Dr. David Burdick as part of a 2023 study.
Mednikova’s sediment addition work in Great Bay also incorporates a new restoration approach: pairing sediment with the addition of the ribbed mussel, Geukensia demissa. Filter-feeding bivalves like ribbed mussels are often incorporated into coastal restoration projects, as they promote growth of aquatic plants through their roles in nutrient cycling and enhancing water clarity. Ribbed mussels also produce sturdy byssal threads to anchor themselves within marsh sediments and plant roots, which could be an especially useful function in sediment addition projects. With guidance from UNH Assistant Professor Dr. Brittany Jellison, who specializes in marine ecophysiology, Mednikova added ten ribbed mussels to a subset of sediment addition plots to assess marsh recovery with and without mussels present.
Mednikova will monitor marsh response to sediment and mussel addition for two years following restoration, using several parameters to assess marsh health. These parameters, which were first monitored before restoration, include vegetation cover, hydrology, pore water chemistry, and species composition of invertebrates within marsh sediments. In collaboration with Dr. Ashley Bulseco, a Postdoctoral Fellow, who joined the Moore lab in Fall 2023, Mednikova is also exploring the response of the soil microbial community to this restoration technique. Microbes such as bacteria and fungi play essential roles within marsh systems, and understanding their response to restoration is an important, yet under-studied research area.
For some additional details on this restoration project and more team photos, see this article published over the summer on UNH Today.