Benthic characterisation of temperate marine habitats using bathymetric LiDAR and video observations

Ecological habitat characterisation, quantifying benthic substrata and sessile biota assemblages, was achieved in this study with the application of bathymetric Light Detection and Ranging (LiDAR) and underwater video observation data. The bathymetric LiDAR system is an aerial mapping system that uses laser detection of seafloor topography to obtain high resolution mapping data over large geographical regions, in shallow aquatic environments. Mapping data was supplemented with video observations of benthic substrata and biota characteristics to ‘ground truth’ the LiDAR survey. Evaluation of bathymetric LiDAR tests the potential of this system for subtidal habitat mapping, representing a novel approach for shallow water habitat characterisation in temperate marine environments. An automated predictive classification method was used to produce one substrata and two benthic biota habitat maps of the Warrnambool to Port Fairy study area from 0-32 m depth. Error assessment of habitat maps determined good overall accuracies (>70%) with varying results for classification of individual habitat classes; e.g. mixed brown algae and sediment substrata, 75% and 89%, respectively. Different algal dominated habitat classes were also successfully distinguished including canopy forming kelp and understorey tufting algae. Non-parametric multivariate analyses (ANOSIM) revealed significant differences in taxa composition between depth strata and habitat complexity categories, while BIOENV analysis indicates the LiDAR derived geophysical variables correlated with the distribution of benthic assemblages observed; e.g. complexity, depth and rugosity. Habitat characterisation using bathymetric LiDAR provides unique baseline information on reef connectivity and the distribution of benthic assemblages, contributing a new perspective for research and management of shallow coastal ecosystems.