The role of turbulence in broadcast spawning and larval settlement in freshwater dreissenid mussels
The role of turbulence has been shown theoretically to influence external fertilization and larval settlement/transport in benthic invertebrates. This is especially true for turbulence generated by bottom roughness in the near-bed region of lakes. This thesis examined the role of bottom roughness created by the presence of freshwater mussels ('Dreissena polymorpha ' and 'D. bugensis') by addressing three objectives: (1) how fertilization success is influenced by water velocity and near-bed turbulence generated by bottom roughness in a laboratory flow chamber and in the field (Evans Point, Lake Erie); (2) how larval transport and settlement is influenced by this near-bed turbulence in laboratory flow chamber and field (Lake Erie) experiments; and (3) how gamete and larval transport are influenced by the ratio of roughness spacing ([lambda]) to roughness height (' k') roughness height under the mussel patch configuration, which was positively associated with turbulent ejections. Results from the CFD modeling, which incorporated a released scalar as a proxy for gamete and larvae, accurately predicted the flow regimes classified using the ratio of [lambda]/' k' (e.g., < 8 for skimming flow and ~8 for wake interference flow), but this varied with the geometry of the modeled roughness elements. These results indicate that the spatial configuration of bottom roughness, including mussels, determines the flow regime (i.e., skimming vs, wake interference flow), which, in turn affects fertilization success and larval transport/settlement in benthic species.