Upper Bay SAV recovery

My PhD dissertation focused on the dynamics of a large bed of submersed aquatic vegetation (SAV) in the upper Chesapeake Bay. What makes this particular SAV bed so special is 1) it’s huge (in fact it’s the largest SAV bed in the Bay) and 2) it suddenly recovered about 10 years ago. My goal was to identify factors that contributed to its recovery and resilience. I used a variety of approaches to answer these questions, including retrospective data analysis, observational and experimental fieldwork, and numerical simulation modeling. I found that reductions in nutrient loading, coupled with exceptional water clarity during several consecutive dry years allowed new plants to colonize the region. Once established, bed expansion was likely accelerated by positive feedback processes, whereby the plants modified their environment in ways that improved their own growth. The work also showed that feedbacks involving interactions between the plants, water movement, suspended sediments, and nutrients enabled the SAV bed to resist damage from high flow and sediment loading rates associated with a major flood event and remain stable despite decreased but nonetheless high nutrient loading rates. These findings are significant because they suggest that efforts to reduce nutrient loading to the system may be working to induce ecological recovery. However, this case serves as an example that restoration in response to nutrient reductions can be sudden and surprising due to nonlinearities associated with internal feedbacks.

This project was funded by Maryland Sea Grant, University of Maryland Center for Environmental Science Horn Point Laboratory, and the Concordia Foundation