Acoustic Remote-Sensing of Reef Benthos in Broward County, Florida (USA)

Benthic assemblages of variable density cover three progressively deeper ridges that parallel the Broward County, Florida, coast. An acoustic bottom classification survey using QTCView5 with a 50 kHz transducer showed different acoustic classes on the shallow reef-ridge and the two deeper reef-lines, which both showed the same acoustic signature. Ground-truthing showed that the differences in acoustic signature corresponded to different benthic assemblages: nearshore hardgrounds had low live cover and were dominated by algae covering substrate, the two deeper reef-ridges had the same acoustic signature and similar benthic assemblages (dominated by sponges and gorgonians). The QTCView5 was also able to differentiate between stable sands covered by a thin red algae turf and more mobile sand without turf cover. Acoustic remote-sensing methods can be used to differentiate benthic assemblages, as long as enough differences exist in the growth-form characteristics of the dominant species to provide for a different acoustic roughness.