Aerial remote sensing and spatial analysis of marine benthic habitats in St George’s Bay (Malta)

Abstract

The spatial distribution of marine benthic assemblages and habitats present in St George’s Bay (St Julians, Malta) was mapped using aerial photography and GIS techniques as part of an environmental monitoring programme to assess the potential impacts of beach replenishment works carried out in the bay. Maps showing the distribution of benthic habitats in the study area were produced in May 2004 (prior to initiation of the beach replenishment works), and in April 2005 (one year following the beach replenishment works). On both occasions, data from the maps was ground-truthed by SCUBA divers, who also collected data on the occurrence of characteristic plant and animal species from each habitat type. The results from the remote techniques and diving surveys indicated the presence of four main benthic assemblage types in the study area: (i) an assemblage of bare sand; (ii) an assemblage of photophilic algae on hard substrata; (iii) Posidonia oceanica meadows; and (iii) Cymodocea nodosa meadows. Comparison of the map produced in 2004 (pre-replenishment) with the one produced in 2005 (post-replenishment) indicated that, following the beach replenishment works, the main changes in the distribution of benthic assemblages and habitats in the study area consisted of: (i) a decrease in coverage of assemblages of bare sand; and (ii) a corresponding increase in coverage of supralittoral sand habitat. Overall, the results from the first year of environmental monitoring showed that the beach replenishment works did not have any adverse impacts on the marine benthic assemblages and habitats of the area. The results are discussed in the light of use of aerial photography and GIS techniques for the first time locally to monitor potential adverse impacts from coastal development works on marine benthic habitats.