Characterizing Seagrass Exposure to Light Attenuation and Turbidity Associated with Dredging Activity in the Gulf Intracoastal Waterway, Sarasota Bay, Florida
U.S. Army Engineer Research and Development Center Vicksburg United States
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This technical note describes the collection of light attenuation and turbidity data associated with a dredging event conducted by the U.S. Army Corps of Engineers USACE special purpose dredge the Murden. Light attenuation is a measurement of the loss of light that photosynthetic aquatic resources depend on for survival while turbidity is water clarity standard used in the regulatory system as a quick and easy technique to assess water quality degradation. There are several ways dredging activities can impact environmental resources direct physical disturbance, increased light attenuation through the water column, abrasion of the leaves, sediment settling on blades, and burial due to sedimentation. Potential dredging effects on seagrasses can be classified into two types direct and indirect. Direct impacts are defined as the physical removal of existing submerged aquatic vegetation within the dredging footprint. Indirect impacts to seagrasses may occur in areas near the dredged areas but not physically disturbed by the dredging equipment, due to temporary increases in water column light attenuation or sedimentation. Indirect impacts are more challenging to detect against a background of natural spatial and temporal variability. This technical note includes details of the field data collection and comparisons among the various types of data.
- Civil Engineering