Geology - benthos relationships on a temperate rocky bank, eastern Bass Strait, Australia

Abstract

To better understand the possible relationships between the geology of the seabed and the associated biological communities, a multibeam sonar survey over New Zealand Star Bank in the eastern Bass Strait was conducted. A hierarchical method of benthic habitat mapping was applied to the secondary biotope and biological facies levels at the site (<10 km) scale. Four secondary biotopes and four biological facies have been defined on the basis of geomorphology revealed by the bathymetry model and the results of statistical analysis of the sediment and underwater video transect data over the bank. The major differences that control the distribution of biological communities in the New Zealand Star Bank area appear to be related to variations in substrate.(1) Hard-ground features related to high-relief granite outcrops are associated with diverse and abundant sessile and motile fauna. These faunal communities may be biologically modified to patchy barrens habitat by grazing urchins.(2) Unconsolidated sediment on a flat seabed is associated with sparse small sponges on the inner shelf. On the middle shelf and seaward of bank, the flat and muddy seabed supports a community dominated by infauna.(3) Unconsolidated sediment on a low-relief seabed is associated with an increase in the density and sizes of sponges concentrated on any low-relief feature raised above the surrounding flat seabed.

The state of chondrichthyan taxonomy and systematics

“…Improved survey methods, particularly the use of side-scan sonar to provide detailed benthic maps to assess habitat (e.g. Beaman et al 2005), have enabled more strategic survey approaches to be adopted. However, dedicated deepwater surveys from large oceanic trawlers are expensive and few vessels have the capability of surveying the deep continental slopes and ocean basins.…”

Developments in mapping of seabed habitats for Marine Protected Area planning and monitoring

“…However, many of these scales are considerably coarser than that required for the assessment of the distribution of biological habitats and communities which often exist at the scale of metres to kilometres [6]. They are also considerably coarser than the scale at which the majority of seabed mapping data is collected.…”

“…The maximum depth suitable for these methods is determined to a large extent by water clarity, and in many locations this depth can be less than 5-10 m. The data is also restricted to raster or vector layers of habitat classes, such as seagrass, mangrove and saltmarsh [3], with no information on bathymetry. Mapping of deeper subtidal habitats is generally conducted using acoustic tools, which in recent years has developed from using single-beam echosounders that require considerable mapping interpolation [5] to swath echosounders that can provide full coverage of bathymetry and backscatter at high resolution [6,7]. Mapping classes delineated using acoustic remote sensing and associated ground truthing are commonly based on geophysical features [7,8,9] or a combination of biological and physical features [10].…”

Broad-scale ecological distribution of dominant macrozoobenthic taxa ofthe northern Cilician shelf, eastern Mediterranean Sea: crustaceans*

“…The effects of those gradients occur in different ways, resourced by induced variables (chemicals, nutrients, and energy consumption), direct variables (grain size of sediment and temperature), and indirect variables (depth and latitude) (Meynard and Quinn, 2007). Substrates and habitat, such as hard and soft bottoms and vegetative marine beds, play an important role in biodiversity patterns (Williams and Bax, 2001;Beaman et al, 2005;Beaman and Harris, 2007). There is richer biodiversity in seagrass beds than in sandy and muddy soft bottoms, and this diversity drives the increase of biodiversity in adjacent regions.…”