Interdependencies between biological communities, their activities and the sediment environment in determining the acoustic properties of the shelf seafloor
Abstract
Ocean bottom sensing using acoustics is critically important to naval operations, such that anincorrect or inaccurate sediment characterisation can have a substantive impact on operationsand planning. A significant challenge in characterising the seafloor is that acoustic reflectionand scattering from the seabed are highly dependent on the source, composition, and stabilityof the sediment which, in turn, can vary considerably both spatially (cm to km) and temporally(diurnal, seasonal, and/or annual scales) due to the influence of biological and geophysicalprocesses. Prediction models of the seafloor exist and provide reasonably good realizationsof seafloor properties, but projections of acoustic reverberation, sediment characterization,and propagation often diverge from field observations because parameterizationsunderpinning operational models predominantly consider geophysical attributes of the system.From this perspective, seabed characteristics effectively equate with the physical substrateand ignore a more holistic view that combines substrate characteristics with the identity andmodus operandi of the resident fauna (Diaz et al. 2004). Sediments harbor a diverse andabundant biological community whose burrowing, irrigation and construction activities(collectively, sensu bioturbation) contribute to variability in sediment bulk properties, such asheterogeneity and interface roughness. Further, the species themselves can form discretesources of acoustic scatter (e.g. bivalve molluscs), as can the traces of activity (e.g. open orinfilled burrows) that differ to the surrounding consolidated sediment. A logical next step is toincorporate how biological communities modify the physics of seafloor sediment in models ofseafloor processes (Snelgrove et al. 2018). Although numerous examples of biological andgeophysical modification of the seafloor exist, their utility is often constrained to a particularcontext and/or species, and the wide range of possible biological and physical interactionsthat can lead to non-additive effects are not generally considered because of the assumednecessity to establish information from all possible species-environment permutations. Hence,little or no information is available for most invertebrate groups and basic data on how speciesmodify the acoustic properties of sediment are yet to be assembled or considered.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Sep 04, 2018
- Source ID
- N000141812812
Entities
People
- Martin Solan
Organizations
- Office of Naval Research
- United States Navy
- University of California Regents