EK80 Water Column Sonar Data Collected During DP09

The strategy for DP09 was to sample six time-series stations north and inside of a mesoscale cyclonic eddy centered at 28˚N, 88 ˚N, both day and night, with three of these stations sampled in duplicate. A seventh station was sampled/sensed near Viosca Knoll to continue examination of pelagic-benthic coupling in areas of active ecosystem restoration and resource management interest (marine mammal and highly migratory fish species aggregations). Patterns in acoustically derived biological scatter through the water column was collected with multi-frequency scientific echosounders (Simrad EK80) operating at 18kHz, 38kHz, 70kHz and 120kHz following protocols developed during the NOAA NRDA DAP data collection operations. Specifically, during each cruise, transducers were installed on a rigid pole mounted to the side of the ship, and calibrated at sea for operating conditions following protocols developed during the ONSAP/DAP cruises. The dynamics of the mesopelagic scattering community were examined through the depth dependent scattering responses at both frequencies (18 and 38kHz) as well as through the difference between the mean volume backscattering strength (MVBS; in dB) at 18 kHz and 38 kHz (dMVBS(18-38)). In addition, scatterers in the upper water column (~150m) were examined by analyzing all four available frequencies.