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The effect of settling velocity on the transport of mussel larvae in a cobble-bed river: Water column and near-bed turbulence

Schwalb, Astrid Nadine, Morris, Todd James, Ackerman, Josef Daniel
Limnology & Oceanography: Fluids & Environments 2012 v.2 no.0 pp. 28-40
Lampsilis fasciola, freshwater, hydrodynamics, larvae, models, mussels, prediction, rivers, stream flow, streams, turbulent flow, Ontario
Lay AbstractSimple transport models predict that the distance small organisms such as larvae “drift” downstream in rivers is determined by their settling velocity, the release height, and the stream velocity. However, natural turbulent conditions in a river may also affect the downstream transport and dispersion (spread) of larvae. The main goal of this study was to examine how stream velocity and larval settling velocity (Mucket [Actinonaias ligamentina] and the Wavy-rayed Lampmussel [Lampsilis fasciola] differ by 2.5 times) affect the transport of freshwater unionid mussel larvae in the Grand River, Ontario, Canada. Larvae were released and captured in a series of nets downstream. Larval spread in rivers appeared to be strongly affected by stream flow conditions. Larvae were spread more rapidly with increased stream velocity likely due to increased turbulence in the water. Overall there was a good agreement between measured downstream decrease in capture of larvae and predictions from a 3-dimensional advection–diffusion model that considered the spread due to hydrodynamics. However, in contrast to the predictions of simple transport models, differences in settling velocity had no detectable effect on the transport of larvae. Future studies are necessary to further explore the role of settling velocity and other factors under different stream flow conditions, which may also be important for dispersal of other organisms and particles.