Using passive acoustics for monitoring seagrass beds

This paper discusses the ambient noise acquired during the period of one week, from May 8 to 15, 2013 over a Posidonia oceanica bed in the Bay of la Revellata, Calvi, Corsica. The acoustic receivers were moored at 3 locations with water depth ranging from 2 to 20 m. Simultaneously with acoustic measurements, the dissolved O2 was measured by an array of optodes. Preliminary results have shown that the acoustic noise power measured at various locations in the meadow is highly correlated with dissolved O2 (measured by other methods). Nevertheless, a close inspection of noise waveforms shows impulsive signals with shape similar to those produced by snapping shrimp and other shell fish. This work discusses the challenges faced on using these noise waveforms as ecosystem indicators and particularly to monitor the photosynthetic activity.