Multispectral Multibeam Echo Sounder Backscatter as a Tool for Improved Seafloor Characterization

The establishment of multibeam echosounders (MBES), as a mainstream tool in ocean mapping, has facilitated integrative approaches towards nautical charting, benthic habitat mapping, and seafloor geotechnical surveys. The combined acoustic response of the seabed and the subsurface can vary with MBES operating frequency. At worst, this can make for difficulties in merging the results from different mapping systems or mapping campaigns. However, at best, having observations of the same seafloor at different acoustic wavelengths allows for increased discriminatory power in seabed classification and characterization efforts. Here, we present the results from trials of a multispectral multibeam system (R2Sonic 2026 MBES, manufactured by R2Sonic, LLC, Austin, TX, USA) in the Bedford Basin, Nova Scotia. In this system, the frequency can be modified on a ping-by-ping basis, which can provide multi-spectral acoustic measurements with a single pass of the survey platform. The surveys were conducted at three operating frequencies (100, 200, and 400 kHz), and the resulting backscatter mosaics revealed differences in parts of the survey area between the frequencies. Ground validation surveys using a combination of underwater video transects and benthic grab and core sampling confirmed that these differences were due to coarse, dredge spoil material underlying a surface cover of mud. These innovations offer tremendous potential for application in the area of seafloor geological and benthic habitat mapping.

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Benthic habitat mapping with acoustic seabed classification

MTS/IEEE Oceans 2001. An Ocean Odyssey. Conference Proceedings (IEEE Cat. No.01CH37295) ◽

10.1109/oceans.2001.968415 ◽

2002 ◽

Cited By ~ 1

Author(s):

J.L. Galloway

Keyword(s):

Habitat Mapping ◽

Benthic Habitat ◽

Seabed Classification

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Quantification of Spatial and Thematic Uncertainty in the Application of Underwater Video for Benthic Habitat Mapping

Marine Geodesy ◽

10.1080/01490419.2013.877105 ◽

2014 ◽

Vol 37 (3) ◽

pp. 315-336 ◽

Cited By ~ 16

Author(s):

A. Rattray ◽

D. Ierodiaconou ◽

J. Monk ◽

L. J. B. Laurenson ◽

P. Kennedy

Keyword(s):

Habitat Mapping ◽

Benthic Habitat ◽

Underwater Video

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Integrating Towed Underwater Video and Multibeam Acoustics for Marine Benthic Habitat Mapping and Fish Population Estimation

Geosciences ◽

10.3390/geosciences11040176 ◽

2021 ◽

Vol 11 (4) ◽

pp. 176

Author(s):

Alexander R. Ilich ◽

Jennifer L. Brizzolara ◽

Sarah E. Grasty ◽

John W. Gray ◽

Matthew Hommeyer ◽

...

Keyword(s):

Spatial Scales ◽

Video Data ◽

Fish Abundance ◽

Habitat Mapping ◽

Benthic Habitat ◽

Underwater Video ◽

High Definition ◽

Habitat Types ◽

Total Fish ◽

Rocky Habitats

The west Florida shelf (WFS; Gulf of Mexico, USA) is an important area for commercial and recreational fishing, yet much of it remains unmapped and unexplored, hindering effective monitoring of fish stocks. The goals of this study were to map the habitat at an intensively fished area on the WFS known as “The Elbow”, assess the differences in fish communities among different habitat types, and estimate the abundance of each fish taxa within the study area. High-resolution multibeam bathymetric and backscatter data were combined with high-definition (HD) video data collected from a near-bottom towed vehicle to characterize benthic habitat as well as identify and enumerate fishes. Two semi-automated statistical classifiers were implemented for obtaining substrate maps. The supervised classification (random forest) performed significantly better (p = 0.001; α = 0.05) than the unsupervised classification (k-means clustering). Additionally, we found it was important to include predictors at a range of spatial scales. Significant differences were found in the fish community composition among the different habitat types, with both substrate and vertical relief found to be important with rock substrate and higher relief areas generally associated with greater fish density. Our results are consistent with the idea that offshore hard-bottom habitats, particularly those of higher vertical relief, serve as “essential fish habitat”, as these rocky habitats account for just 4% of the study area but 65% of the estimated total fish abundance. However, sand contributes 35% to total fish abundance despite comparably low densities due to its large area, indicating the importance of including these habitats in estimates of abundance as well. This work demonstrates the utility of combining towed underwater video sampling and multibeam echosounder maps for habitat mapping and estimation of fish abundance.

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

Marine and Freshwater Research ◽

10.1071/mf04306 ◽

2005 ◽

Vol 56 (7) ◽

pp. 943 ◽

Cited By ~ 37

Author(s):

Robin J. Beaman ◽

James J. Daniell ◽

Peter T. Harris

Keyword(s):

New Zealand ◽

Statistical Analysis ◽

Habitat Mapping ◽

Benthic Habitat ◽

Underwater Video ◽

Biological Communities ◽

Granite Outcrops ◽

Unconsolidated Sediment ◽

Faunal Communities ◽

Video Transect

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.

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