Dave Fratantoni (WHOI Physical Oceanography) bangs on a pipe near the recorder-equipped gliders to introduce an impulsive sound that helps synchronize the recorders' internal clocks as engineer Paul Fucile (WHOI PO) looks on.

The Woods Hole Oceanographic Institution (WHOI) Autonomous Systems Laboratory (ASL), headed by Dave Fratantoni, operates a fleet of nearly 20 gliders equipped for varying endurance, depth capability, and science payload. These vehicles are designed to explore ocean circulation and the relationships between physics and biology on a variety of scales. A glider operations and data collection system developed by this lab provides integrated control and data management for the efficient operation of large autonomous glider fleets, including real-time data access during field experiments.

The long-term goal of one ASL pioneering glider application, undertaken with WHOI’s Mark Baumgartner, is to investigate the distribution and habitat of marine mammals over time scales of weeks to months by collecting both acoustic recordings and high-resolution oceanographic measurements. Recording vocalization rates and prey distribution simultaneously is difficult with other technologies, so the glider’s capability for doing this allows the researchers to examine the association between the two. In the development phase, the team applied the technology to the ecology of baleen whales, of particular interest because they are endangered. In addition, these whales feed low on the food web, so elucidating their ecology provides insights into the role of mammals in marine ecosystems.

Working in the southwestern Gulf of Maine during May 2005, they outfitted four gliders with acoustic recorders as well as sensors to measure temperature, salinity, chlorophyll fluorescence, currents, and optical backscatter. They focused on associations between sei whale vocalization rates, oceanographic conditions, and vertical distribution of the whales’ copepod prey. Reduced night-time calling by the whales suggests that they are feeding during the copepods’ migration to the surface (they avoid visual predators by staying deep during daylight), while increased daytime calling is likely to indicate a more social time among the whales.