Benthic Habitat Mapping from Seabed Acoustic Surveys: Do Implicit Assumptions Hold?

Abstract

Geological mapping of seabed has a great potential for use in predicting spatial patterns of benthic communities and ecosystems. Recent technological advances in acoustic surveys empower scientists to acquire massive amounts of information on seabed structure, texture, complexity and subsurface. Benthic habitat maps, based on highresolution acoustic surveys, often accompanied by groundtruthing by cores, grab and optical samples have implicit assumptions on relationships between sampled acoustic signal, seabed morphology, texture and biological derivatives, such as community composition. There are two major groups of assumptions on the path from collecting survey data to creating a map of benthic habitats: First is that we can confidently interpret properties of surficial sediments, and the second – that the derived textural or morphological classes are relevant to seabed ecology. The degree of uncertainty behind these assumptions may render the resulting habitat maps useless. The current understanding of sediment-organism relationships, based mostly on studies of sediment grain size, requires urgent revision. Interaction of sediment and flow as an agent of natural disturbance, together with the effects of benthic organisms on this interaction are in the core of benthos-sediment coupling. Better understanding of ecological patterns and physical processes in the benthic boundary layer on a range of spatial scales will allow more efficient use of remote sensing tools and techniques for using geological information as a proxy in benthic ecosystem mapping.