Meeting Abstract

P3.17  Wednesday, Jan. 6  Field boundary layer characteristics as modified by clams in habitats of varying survival rates DELAVAN, Sarah K.*; WEBSTER, Donald R.; Georgia Institute of Technology; Georgia Institute of Technology gth900g@mail.gatech.edu

Previous observations indicate that clam survival rates are higher in and around both oyster beds and sea grass beds than survival rates recorded for mud flats. Flow characteristics in these regions may influence predation rates by creating a refuge from predation. In this regard, clam presence and behavior has the potential to modify the boundary layer momentum distribution and alter the flow refuge from predation depending on the turbulence characteristics of the background flow. To determine the effect of the presence and pumping behavior of the bivalve clam, Mercenaria mercenaria, on the boundary layer momentum distribution, velocity profiles were collected for flood tides in the tidal rivers adjacent to Wassaw Sound, Georgia, USA. Velocity profiles were collected simultaneously with two adjacent Acoustic Doppler Velocimeters for boundary layer flows above sediments with and without the presence of buried clams. Treatment sites included clams buried in mud sediments, sand sediments, downstream of oyster beds, and downstream of sea grass beds. Vertical profiles of mean velocity, turbulent kinetic energy, and Reynolds shear stress are calculated from the collected time records. We hypothesized that the modification of the vertical profiles is unique to the treatment characteristics. Preliminary analysis suggests that flows downstream of sea grass and oyster beds are less affected by the presence of clams than flows over sand and mud flats. Clam presence reduced the velocity above mud substrates in all three coordinate directions compared to the adjacent measurements without clams present, particularly close to the substrate. Conversely, clams in sand sediments increase the average velocity.