Spatially quantitative seafloor habitat mapping: Example from the northern South Carolina inner continental shelf
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Resource Abstract:
Naturally occurring hard bottom areas provide the geological substrate that can support diverse assemblages of sessile benthic
organisms, which in turn, attract many reef-dwelling fish species. Alternatively, defining the location and extent of bottom
sand bodies is relevant for potential nourishment projects as well as to ensure that transient sediment does not affect reef
habitats, particularly in sediment-starved continental margins. Furthermore, defining sediment transport pathways documents
the effects these mobile bedforms have on proximal reef habitats. Thematic mapping of these substrates is therefore crucial
in safeguarding critical habitats and offshore resources of coastal nations. This study presents the results of a spatially
quantitative mapping approach based on classification of sidescan-sonar imagery. By using bottom video for image-to-ground
control, digital image textural features for pattern recognition, and an artificial neural network for rapid, quantitative,
multivariable decision-making, this approach resulted in recognition rates of hard bottom as high as 87%. The recognition
of sand bottom was less successful (31%). This approach was applied to a large (686 km2), high-quality, 2-m resolution sidescan-sonar
mosaic of the northern South Carolina inner continental shelf. Results of this analysis indicate that both surficial sand
and hard bottoms of variable extent are present over the study area. In total, 59% of the imaged area was covered by hard
bottom, while 41% was covered by sand. Qualitative spatial correlation between bottom type and bathymetry appears possible
from comparison of our interpretive map and available bathymetry. Hard bottom areas tend to be located on flat, low-lying
areas, and sandy bottoms tend to reside on areas of positive relief. Published bio-erosion rates were used to calculate the
potential sediment input from the mapped hard bottom areas rendering sediment volumes that may be as high as 0.8 million m3/yr
for this portion of the South Carolina coast. ?? 2003 Elsevier Ltd. All rights reserved.
Citation
Title Spatially quantitative seafloor habitat mapping: Example from the northern South Carolina inner continental shelf