Core and resonance logger (CARL) measurements of fine-grained sediments containing infauna Free

Benthic infauna perform important ecological functions such as water filtration, the recycling of organic matter, and forage for larger predators. However, how infauna affect bulk acoustical properties of the sediment is less studied and warrants further investigation. During a field experiment conducted in Petit Bois Pass, AL, multiple cores of fine-grained sediments containing infauna were collected by divers and analyzed using a core and resonance logger (CARL). CARL is a core-logger capable of performing both conventional pitch-catch measurements radially along the core as a function of depth and lower frequency resonance measurements. Resonance measurements were performed by exciting acoustic modes within the core and sensing them externally along the core's length. By utilizing both pitch-catch transducers as receivers, symmetric and asymmetric modes can be identified, and sound speed can be inferred as a function of frequency. The frequency ranges for the pitch-catch and resonance measurements were 100 kHz to 300 kHz and 8 kHz to 23 kHz, respectfully. Subsequently, the cores were sectioned and were either sieved for infauna or analyzed for porosity and grain size distribution. The measured sound speeds will be compared with biological and geological properties of each individual core.