Detecting Mesopelagic Organisms Using Biogeochemical-Argo Floats

During the North Atlantic Aerosols and Marine Ecosystems Study in the western North Atlantic, float‐based profiles of fluorescent dissolved organic matter and backscattering exhibited distinct spike layers at ∼ 300 m. The locations of the spikes were at depths similar or shallower to where a ship‐based scientific echo sounder identified layers of acoustic backscatter, an Underwater Vision Profiler detected elevated concentration of zooplankton, and mesopelagic fish were sampled by a mesopelagic net tow. The collocation of spike layers in bio‐optical properties with mesopelagic organisms suggests that some can be detected with float‐based bio‐optical sensors. This opens the door to the investigation of such aggregations/layers in observations collected by the global biogeochemical‐Argo array allowing the detection of mesopelagic organisms in remote locations of the open ocean under‐sampled by traditional methods.
Key Points We present concurrent observations of mesopelagic organisms with echo sounders, a camera, a net tow, and profiling floatsLayers of mesopelagic organisms coincide with distinct spike layers in fluorescence and backscattering profilesNovel application of biogeochemical‐Argo float enables the detection of mesopelagic organisms and their migration