Mass Exchange between Flexible Submerged Canopies and Adjacent Open Water

Massachusetts Institute Of Technology, Cambridge MA

Investigators

Abstract

Seagrass meadows have a significant ecologic and economic impact in coastal regions. The nutrient cycling they provide is valued at 3.8 trillion dollars per year. In addition seagrass beds provide habitat for many economically important marine species and influence the fate of sediment and carbon in the coastal-zone. The important biogeochemical processes within a seagrass meadow, as well as the impact of seagrass on the surrounding environment, are regulated by the exchanges of momentum and mass between the meadow and surrounding open water. Several previous studies have described the mass and momentum transport associated with rigid canopies. However, we have only a limited understanding of transport in flexible canopies. This project will build on existing theories for rigid canopies to develop mass transport models for flexible canopies under both unidirectional flow and wave conditions. Intellectual Merit: The project will develop new models for turbulent exchange in flexible submerged canopies under both unidirectional flow and wave conditions. This work will contribute to our basic understanding of bio-flow interaction. In addition, the work contributes to the broad topic of flow and transport near porous layers that touches disciplines in meteorology (terrestrial canopies), porous media (hyporheic exchange), and biological oceanography (kelp forest, seagrass, coral ecology) Broader Impacts and Potential Benefits to Society: By providing physical models for flux in and around flexible, submerged vegetation, this project will contribute to a better framework for studying and measuring the uptake, settling, and recruitment processes that occur within these canopies. In addition, the flux models will enable a more quantitative consideration of how meadow geometry (length, height, stem density) influences a meadow?s impact on the surrounding ecosystem, which in turn will lead to better predictions of ecosystem response to changes in nutrient load or changes in seagrass distribution. In addition, the project will provide training for one graduate and at least one undergraduate student per year. The project will also form the basis for a new undergraduate laboratory activity, to be incorporated into the Principal Investigator?s current Junior year course. Finally, the investigator will use this work as a platform for continued interaction with the MIT Seagrant Eelgrass Restoration Project.