Abstract
Turbulence and sound are important cues for oyster reef larval
recruitment. Numerous studies have found a relationship between
turbulence intensity and swimming behaviors of marine larvae, while
others have documented the importance of sounds in enhancing larval
recruitment to oyster reefs. However, the relationship between
turbulence and the reef soundscape is not well understood. In this study
we made side-by-side acoustic Doppler velocimeter turbulence
measurements and hydrophone soundscape recordings over 2 intertidal
oyster reefs (1 natural and 1 restored) and 1 adjacent bare mudflat as a
reference. Sound pressure levels (SPL) were similar across all three
sites, although SPL > 2000 Hz was highest at the restored
reef, likely due to its larger area that contained a greater number of
sound-producing organisms. Flow noise (FN), defined as the mean of
pressure fluctuations recorded by the hydrophone at f < 100
Hz, was significantly related to mean flow speed, turbulent kinetic
energy, and turbulence dissipation rate (ε), agreeing with theoretical
calculations for turbulence. Our results also show a similar
relationship between ε and FN to what has been previously reported for ε
vs. downward larval swimming velocity (wb), with both FN and wb
demonstrating rapid growth at ε > 0.1 cm2 s-3. These
results suggest that reef turbulence and sounds may attract oyster
larvae in complementary and synergistic ways.