Effects of airgun operations on targets in the deep scattering layer

Seismic surveys, commonly used for oil and gas exploration, rely on airgun operations that produce intense, low-frequency acoustic impulse signals. These signals have the potential to disrupt ocean ecosystems by altering targets’ spatial distribution and triggering behavioral changes. To better understand these potential impacts, we conducted a joint airgun/REMUS operation focusing on biological targets in the deep scattering layer (DSL). A single airgun (210 c.u.) was fired at controlled intervals while the REMUS autonomous underwater vehicle—equipped with a broadband echosounder (38 and 70 kHz), hydrophones, and precise navigational tools—collected data at two specific depths (300 and 550 m) and relatively short slant range (<500 m) from the airgun source. Acoustic target strength (TS) data were recorded to observe potential responses, including changes in individual target behavior at different depths as well as overall layering or patchiness of the DSL. This presentation shares preliminary observations on potential target movement dynamics, startle responses, and vertical or horizontal aggregation shifts due to airgun sounds. [Work supported by the Office of Naval Research.]