Acoustic seabed classification applied to Baltic benthic habitat studies: a new approach

摘要

The application of acoustic methods for the classification of bottom habitats is based mostly on the analysis of measured parameters without relating them to the bathymetric structure. Geological complexity and biological patterns are closely related to bathymetry. This paper presents a new approach to the acoustic classification of bottom habitats in that it combines the distribution of a selected acoustic parameter with its bathymetric structure. The hypothetical effective angle of a bottom echo θ'/2, corresponding to its normalised length, was the acoustic parameter applied. This parameter broadly characterises the complex acoustic reflecting and scattering properties of the seabed. Its highest values correspond to a layered bottom consisting of soft sediment. The southern Baltic area was classified by a direct comparison of two factors measured acoustically: the statistical distribution of θ'/2, and the correlated depth structure within selected standard regular geographical areas (15' latitude and 30' longitude) which the total area was divided into. The area size was matched with the density of the measurements collected. The same factors were also estimated for the whole southern Baltic. The study was based on soundings collected on board r/v "Baltica" during regular acoustic surveys in 1995-2003. The classification applied provides a new possibility of complex seabed identification and comparison of seabed structure dynamics, useful in benthic research and in the ecologically based administration of marine areas.