![]() The deposition of sediment from dredging or other human activities can be harmful to eggs and larvae through burial or encasement of eggs in fine particles occupying interstitial spaces, and these earlier stages are unable to avoid this stressor because of their limited mobility. ![]() For all fish species in which effects to early life stages have been measured, it is clear that eggs and larvae are the most sensitive to suspended sediments and sediment deposition. Assessing exposure of listed species to elevated levels of turbidity or TSS concentration requires an understanding of the sources (e.g., dredge type), factors that influence the duration and intensity of exposure (e.g., sediment type and/or current), as well as the individual species tolerance to the anticipated level of exposure at a given life stage. After reviewing the available studies relative to the ESA-listed species in the Greater Atlantic Region - Atlantic salmon, Atlantic sturgeon, shortnose sturgeon, large whales, and sea turtles - we believe the effects of turbidity and suspended sediment are greatest for fish species. Understanding how local conditions influence turbidity and re-suspended sediment, and using site-specific information in the consultation is encouraged. If information is available on how conditions (e.g., bathymetry, currents) and material (e.g., sand versus silt) may influence turbidity and re-suspended sediment at a site, action agencies and applicants should consider it in addition to the general guidance provided below. ![]() Turbidity (an optical quality of light transmission through a fluid containing sediment particles most often measured as nephelometric turbidity units) and Total Suspended Sediment concentration (TSS, a gravimetric measure of particles in suspension generally measured as milligrams per liter) are not directly comparable without calibration of instrumentation to in situ sediments (Davies-Colley and Smith 2001, Clarke and Wilber 2008).Įffects of the actions described below will vary based on site-specific conditions (Wilber and Clarke 2001). ![]()
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