9503170 McDonald The goal of this planning study is to obtain a preliminary set of field measurements that can be used to estimate the algal consumption rate of zebra mussels in a large lake. The proposed measurements will be performed above a bed of zebra mussels during a period from mid-June to late August at a site in the western basin of Lake Erie that is thermally homogenous and, therefore, not complicated by the effects of stratification. Measurements will include vertical profiles of horizmntal velocities at 25 cm intervals from the mussel bed up to a distance of approximately 3 m above the bottom. Concurrent sampling, at the same vertical resolution, will provide profiles of the phytoplankton concentrations above the bed. These distributions will then be used as input to a one-dimensional equation of phytoplankton concentration that mathematically represents the balance between settling, turbulent mixing, and consumption (by zebra mussels) of phytoplankton at the mussel bed. The velocity profiles will be used to estimate values of the vertical distribution of turbulent diffusivity, which together with the phytoplankton concentration profiles and estimates of settling rates obtained from the literature, provide enough information to estimate zebra mussel consumption directly.
