Acoustic-based classification of marine geophysical data for benthic habitat mapping in the littoral zone of Qaitbay Citadel of Alexandria

Acoustic-based classification of marine habitats using multi-platform geophysical technologies has proven to be a very efficient tool for marine conservation plans and coastal resources management. This work is the first descriptive study that focused on acoustic mapping and classification of benthic habitats in the littoral zones of Qaitbay Citadel in front of Pharos Island in Alexandria. The sonar image processing distinguished three different seafloor patterns according to the degree of backscattered signals. Submerged barrier reefs were detected among different forms of seagrass beds in front of Qaitbay Citadel. These seagrass habitats were found either on sedimentation or on matte base. Rocky habitats were located along the artificial breakwaters of the Eastern Harbor, reflecting the impact of the emerging breakwaters on the benthic communities. Habitat measurements were performed including the thickness of seagrass and matte layers across the sub-bottom reflection profiles, which helped in the establishment of a habitat thickness map. These datasets integration showed three different seafloor backscatter patterns indicating the presence of six different habitat classes on the seafloor of the study area. This habitat classification provides useful information that supports the design of future conservation plans for benthic habitats and marine life in the studied area.