A key task in restoring
the Chesapeake Bay's oyster population is finding appropriate locations to plant
oyster spat and place materials on which spat will grow. Oyster will
grow on almost any stationary hard surface (substrate) and in a variety of aquatic
environments. However, a commercially sustainable oyster population requires
optimal growing conditions, including appropriate growing surfaces, suitable water
quality and low sedimentation rates.
Discovery of bay bottom conditions using traditional
methods requires expensive and time-consuming sampling programs or visual inspection
using
divers or
cameras. However,
recent developments in remote-sensing technology have made mapping bay bottom characteristics
more efficient
and less costly. Onboard DNR's R/V
Kerhin, Maryland Geological Survey has the capability
to map the bay bottom and subsurface geology using acoustic remote sensing systems. These
systems include:
- side scan sonar for imaging bottom surface conditions;
- acoustic seabed classification
to determine sea floor sediment and habitats;
- seismic profiling for stratigraphic
analysis;
- underwater video camera arrays for visualization of bottom conditions.
The Coastal
and Estuarine Geology program participates in several oyster
restoration projects around the Chesapeake Bay, including the Poplar
Island Environmental Restoration Project and the Oyster
Bed Mapping Project. This
work will lead to a more thorough understanding of bay bottom
conditions and how they affect the
growth
and health of oyster populations in tidewater Maryland.
Information about MGS oyster restoration projects can be
found at the following links.
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- side
scan imaging (for more information see EdgeTech
Marine)
The side-scan sonar system ensonifies the sediment surface as well as a thin near-surface
layer and presents results that enable interpretation of the surficial characteristics
of the bottom. These characteristics would include presence of oyster shells, small
to large scale surface features such as sand waves, topographic breaks and items
that stand above the bottom, as well as differentiation of soft muddy bottom sediments
from areas composed of sandy sediments. The aerially continuous nature of the resultant
data enables maps of the bottom to be readily developed.
- seismic
profiling (for more information see Knudsen
Engineering, Ltd)
The sub-bottom profiling equipment ensonifies
the layers of sediments directly below the boat path thus enabling an internal
view of the sediment layers that
occur below the sediment water interface. These results may be used to determine
internal layers of sediments that may have resulted from changes in sedimentation
rates, alterations in currents and river flow characteristics, and resulting
burying of bottom features including oyster bars.
- acoustic
sea floor classification (for more information see QuesterTangent)
The acoustic sediment classification system also ensonifies the bottom directly
below the vessel path, and the results can be used to classify the surficial
sediments into areas with differing acoustic characteristics. The acoustic differences
can be linked to such things as variations in the sediment composition related
to grain size, the presence of differing populations of benthic infauna and epifauna,
and the presence and density of submersed aquatic vegetation and macroalgae.
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