To explore and define the roles of organisms in the marine environment, biological oceanographers may use a variety of research tools and techniques. These may include shipboard sampling, computer modeling, high-resolution video analysis, bio-optics, and/or acoustics. For example, archival marine acoustic recording units (ARUs) , such as the Ecological Acoustic Recorder (EAR), are used to monitor the ambient sound field of coral reefs and other tropical systems. Biological oceanographers may also use acoustics to study plankton. Plankton are relatively small organisms whose movements are dominated by currents, though many can swim. Sonar systems, similar to fish finding sonars , can be used to study plankton and fish abundance and distribution.
Marine fishes and mammals produce underwater sounds and scientists can listen for these sounds, using tools such as hydrophones, hydrophone arrays, and other passive acoustics sensors, and detect different marine animal species. acoustic gliders are a type of ocean glider that includes a hydrophone, can work continuously in all weather conditions for long time periods, possess a suite of high-resolution oceanographic sensors, and operate silently (because they do not have an engine or propeller). Researchers use acoustic gliders to study whale distribution, behavior, and habitat. Acoustic gliders have been used to study Sei whales , North Atlantic Right whales, and Beaked whales. They have also been used to track acoustically tagged fish. Estimating abundance (population size), animal density (number of animals per unit area), and the overall distribution of marine animals is critical to understanding marine ecology as well as making important and effective management and conservation decisions.