Abstract
Extensive seabed sediment mapping is highly relevant to describe marine ecosystems and to quantify the distribution and extent of benthic habitats. Compared to traditional mapping methods, primarily based on bed sampling, multibeam echo sounding (MBES) is a time-efficient tool to acquire high-resolution bathymetric and backscatter data over large areas. We use a Bayesian method for unsupervised acoustic sediment classification (ASC) of MBES backscatter data of the Cleaver Bank, Netherlands Continental Shelf. On these sparsely distributed backscatter datasets, we tested and evaluated different Kriging algorithms, showing that Ordinary Kriging results in a reliable map. We introduce a new approach to classify interpolated MBES backscatter based on the Bayesian method for producing full-coverage sediment maps. Comparison to a traditional sediment map and in situ measurements shows that this approach resolves lateral heterogeneities (kilometers). When evaluating the high-resolution sediment map obtained from the Bayesian method, based on the actual backscatter, mapping laterally heterogeneous sediments significantly improved (meters). In order to create the optimal sediment map, we aimed to integrate ASC into existing maps, which, however, requires quantified spatial uncertainties of both considered maps. Finally, the low discrimination power of MBES backscatter for coarse sediments is highlighted as a shortcoming of current ASC mapping.
Highlights
Increasing human activities in the marine environment, such as fisheries or dredging, affect seabed habitats worldwide (Kaiser et al, 2003; Halpern et al, 2008; Foden et al, 2010; Erftemeijer et al, 2012; Korpinen et al, 2013)
The backscatter data retrieved from the beam angle of 48° (± 1°, 47°–49°) at starboard-side are used for the interpolation
In order to find a suitable interpolation method for the generation of full-coverage sediment maps of the multibeam echo sounding (MBES) data, we compare the results of Ordinary Kriging (OK), Simple Kriging (SK), Universal Kriging (UK) as well as Ordinary Cokriging (OCK), Simple Cokriging (SCK) and Universal Cokriging (UCK)
Summary
Increasing human activities in the marine environment, such as fisheries or dredging, affect seabed habitats worldwide (Kaiser et al, 2003; Halpern et al, 2008; Foden et al, 2010; Erftemeijer et al, 2012; Korpinen et al, 2013). The impacts depend on the magnitude and frequency of the human activities, and vary with the marine ecosystem in which they occur (Halpern et al, 2015). To assess the anthropogenic impact on the seabed ecosystem and to develop suitable management strategies, it is necessary to identify the spatial variability of benthic habitats. Marine in situ measurement techniques (e.g. grabs, cores and underwater video footage) reveal detailed information of the sediment properties and generate, in general, an accurate representation of the local seabed. The density and coverage of bed sampling are not always sufficient to represent the sediment heterogeneity on the required spatial scales
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