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Title: Ecological risk assessment of the effects of the incremental increase of commercial navigation traffic (improvement scenarios 2 and 3) on freshwater mussels in the main channel and main channel borders
Authors: United States. Army. Corps of Engineers. Rock Island District.
United States. Army. Corps of Engineers. St. Louis District.
United States. Army. Corps of Engineers. St. Paul District.
Cadmus Group.
EcoHealth Research, Inc.
Keywords: Ecological risk assessment
Impacts of commercial navigation on mussel growth and reproduction
Mussel bioenergetics model
Threeridge mussel
Amblema plicata
Issue Date: Sep-2003
Publisher: Environmental Laboratory (U.S.)
Engineer Research and Development Center (U.S.)
Description: Technical report
Abstract: The Navigation Study Mussel Ecological Risk Assessment presents an assessment of the potential ecological risks posed by commercial traffic on freshwater mussels that live in the main channel and main channel borders of the Upper Mississippi River-Illinois Waterway (UMR-IWW) System. Backwaters were not included in this risk assessment. The assessment examines the possibility that commercial vessel-induced increases in suspended sediments might impair the growth and reproduction of freshwater mussels. Risks to mussels posed by commercial traffic resulting from two improvement scenarios were evaluated. Scenario 2 consists of guidewall extensions at UMR Locks 20-25 to be in place by 2008, while Scenario 3 consists of guidewall extensions at UMR Locks 14-18 and lock extensions at UMR Locks 20-25 to be in place by 2012. The scenarios are presented as increases in the average daily number of vessels traversing each pool on the UMR-IWW System (i.e., tows/day). The threeridge mussel (Amblema plicata) was selected to represent the freshwater mussel community in the UMR-IWW System. It is one of the most common species and is widespread throughout the UMR-IWW System. Additionally, it is one of the most important commercially harvested species. A bioenergetics model for the threeridge mussel was developed and implemented for locations in the UMR-IWW System where mussel beds are known to occur. Freshwater mussel bed locations are included in a geographic information system (GIS) data base. For this risk assessment, selected locations included mussel beds in UMR Pools 13 and 26 and the IWW LaGrange Pool. Results of the model simulations indicated that increases in suspended sediment concentrations associated with traffic increases resulting from Scenarios 2 and 3 do not affect the growth and reproduction of threeridge mussels for five locations in Pool 13, three locations in Pool 26A, one location in Pool 26B, and fifteen locations in the LaGrange Pool. The Navigation Study Mussel Ecological Risk Assessment was organized according to the fundamental components of the ecological risk assessment process: problem formulation, analysis (characterization of exposure and characterization of ecological effects), and risk characterization. The risk assessment methodology described in this report has been developed to assess the potential ecological impacts associated with the anticipated growth of commercial traffic navigating the UMR-IWW System for the period 2000-2050. Assessments of potential impacts on early life stages of fish, adult fish, and fish spawning habitat, as well as impacts on the breakage, growth, and reproduction of submerged aquatic plants, have concurrently been developed. The next phase in assessing traffic impacts on mussels will be to incorporate the current methodology into a framework that characterizes risk in probabilistic terms. More detailed, probabilistic assessments will be performed for selected locations and traffic scenarios identified by the preliminary analyses. Parameters used in the calculations (e.g., suspended sediment concentrations produced by the NAVSED model, mussel growth and filtering rates) that are imprecisely known will be defined as statistical distributions. Monte Carlo simulation methods will be used to propagate these uncertainties through the model calculations to produce distributions of impacts on growth and reproduction in relation to specific traffic scenarios. These distributions of results can be used to estimate the probability of different magnitudes of impact in a manner consistent with probabilistic risk estimation.
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