Shallow Water Benthic Habitat Mapping

What are benthic habitats and benthic habitat mapping?

The term 'benthic' refers to anything associated with or occurring on the seabed. Benthic habitats are seabed environments with distinct physical, chemical and biological characteristics. The distribution of different types of habitats varies depending on factors such as seabed geology and morphology, wave exposure, water depth, water temperature and occurrence of biological communities. The shallow-water benthic habitats of Australia's coastal zone are rated among Australia's most valuable natural resources, based on a variety of biodiversity values and resource potential. Some well known benthic habitat types include seagrass beds, kelp forests, coral reefs and sand banks. There are a range of methods used to identify the distribution of benthic habitats that collectively fall under the banner of benthic habitat mapping.

How do we map benthic habitats?

Benthic habitat mapping usually requires the deployment of remote sampling techniques because of the problems of access and cost that are inherent in directly surveying large areas of the seabed. These indirect methods usually include obtaining seabed data from a variety of ship-mounted sonar techniques and video systems, as well as a range of satellite or airborne scanners. It is standard practice to incorporate some traditional 'direct' sampling (i.e. surveys by scuba divers; ship-based seabed sampling by grab or core samplers) into benthic mapping surveys in order ground-truth (or better understand) the data obtained by the indirect methods.

Benthic habitats are usually classified based on a range of data types that involves various methods of spatial analysis, which itself is a rapidly evolving area of research. More detailed information on acoustic, electro-optical and physical sampling techniques are available in the technical section.

Why map benthic habitats?

Data derived from shallow water benthic habitat mapping techniques can provide fascinating insights into important seabed characteristics, and have led to the discovery of submerged coral reefs, river palaeo-channels and mobile seabed sediment. The application of multi-beam (or 'swath') sonar systems in coastal and marine waters can now provide seafloor bathymetry and textural information at unprecedented decimetre-scales. GIS methods have evolved alongside the advancements in sonar technology, and GIS products derived from multi-beam data are now widely used in coastal management.

Some specific management drivers for benthic habitat mapping are listed below:

Fisheries resource assessment

The management of certain habitats is critical to ensure ongoing and sustainable fisheries resources, as key habitats provide spawning, nursery, refuge, and foraging grounds for economic species.

Biodiversity values

The assessment of physical features of the seabed can give important insights into the extent, character and diversity of benthic habitats, and their relationships to valued biota. Prediction of biological distribution from physical features is known as habitat 'surrogacy'. Conservation initiatives benefit from knowing the distribution of valued species or their surrogates. The location of Marine Parks can be more effectively planned with detailed knowledge of the distribution of high-conservation value habitats.

Navigation and military applications

An understanding of the depth and physical composition of the seabed is critical for ensuring safe shipping, identifying dangerous reefs and shoals, planning dredging procedures, and assessing the potential for mine burial.

Aesthetics and tourism

Many benthic habitats have important aesthetic values, and are critical for ecotourism operations (e.g. coral reef environments), and also for recreational boating, fishing and diving.