Abstract
Abstract Maps of surficial sediment distribution and benthic habitats or biotopes provide invaluable information for ocean management and are at the core of many seabed mapping initiatives, including Norway's national offshore mapping programme MAREANO (www.mareano.no). Access to high-quality multibeam echosounder data (bathymetry and backscatter) has been central to many of MAREANO's mapping activities, but in order to maximize the cost-effectiveness of future mapping and ensure timely delivery of scientific information, seabed mappers worldwide may increasingly need to look to existing bathymetry data as a basis for thematic maps. This study examines the potential of compiled single-beam bathymetry data for sediment and biotope mapping. We simulate a mapping scenario where full coverage multibeam data are not available, but where existing bathymetry datasets are supplemented by limited multibeam data to provide the basis for thematic map interpretation and modelling. Encouraging results of sediment interpretation from the compiled bathymetry dataset suggest that production of sediment grain size distribution maps is feasible at a 1:250 000 scale or coarser, depending on the quality of available data. Biotope modelling made use of full-coverage predictor variables based on (i) multibeam data, and (ii) compiled single-beam data supplemented by limited multibeam data. Using the same response variable (biotope point observations obtained from video data), the performance of the respective models could be assessed. Biotope distribution maps based on the two datasets are visually similar, and performance statistics also indicate there is little difference between the models, providing a comparable level of information for regional management purposes. However, whilst our results suggest that using compiled bathymetry data with limited multibeam is viable as a basis for regional sediment and biotope mapping, it is not a substitute. Backscatter data and the better feature resolution provided by multibeam data remain of great value for these and other purposes.
Highlights
Multibeam echosounder data reveal the seabed in unprecedented detail and provide an excellent basis for geological interpretations and the identification of seabed terrain of ecological relevance
It appears that multibeam technology is largely fulfilling the potential suggested by earlier studies that pioneered the technology for habitat mapping, surficial geology, and to provide information for ocean management (Todd et al, 1999; Kostylev et al, 2001; Gardner et al, 2003; Pickrill and Todd, 2003)
The two independently made interpretations of sediment distribution in the study area are shown in Figure 4, with Figure 4a representing the MAREANO-standard published sediment maps (e.g. Bellec et al, 2009) and Figure 4b the result of interpreting sediment grain size based on the composite Olex–MB dataset
Summary
Multibeam echosounder data (bathymetry and backscatter) reveal the seabed in unprecedented detail and provide an excellent basis for geological interpretations and the identification of seabed terrain of ecological relevance. An earlier review (Brown and Blondel, 2009) shows the advances in processing and interpretation of backscatter data that have accompanied this rise in the use of multibeam echosounders, increasing the utility of multibeam data for habitat mapping and related studies. It appears that multibeam technology is largely fulfilling the potential suggested by earlier studies that pioneered the technology for habitat mapping, surficial geology, and to provide information for ocean management (Todd et al, 1999; Kostylev et al, 2001; Gardner et al, 2003; Pickrill and Todd, 2003).
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