Estuary Bottom Type and Near-bed Velocities in Barnegat Bay

An estuary’s bottom type influences the water flow speeds within the bottom boundary layer of water above the seabed. The water movement in this layer aids in transporting sediment, larvae, and dissolved substances such as oxygen. For example, larger near-bottom flow speeds will lead to more sediment erosion. Tilt Current Meters, or TCMs, allow us to make measurements regarding differences in bottom velocities. TCM instruments were deployed with water level sensors at three sampling sites of varying bottom types (bare, vegetated, and within aquaculture gear) within Barnegat Bay, New Jersey. Data collection occurred in two week periods during the months of March and October 2020. We expected to find the highest near-bed velocities at sampling sites with a bare bottom and the lowest velocities within oyster aquaculture gear due to disruption of the bottom boundary layer flow by the gear. TCM data demonstrated fastest current speeds at the bare bottom site and slowest speeds near the oyster aquaculture, as anticipated. Based on relationships between current speed and sediment erosion, the aquaculture gear site would experience more deposition of sediment and less erosion compared to the bare or vegetated sites. Increased deposition allows for the settlement of sediment and other particulate matter such as seagrass seeds, which would further impact estuary bottom type and near-bed velocities.