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1. River Flow 2020 Proceedings of the 10th Conference on Fluvial Hydraulics (Delft, Netherlands, 7-10 July 2020)

   https://doi.org/https://doi.org/10.1201/b22619  

   Wu, H.; Constantinescu, G (August 2020, River Flow 2020)

   Wim Uijttewaal, Mário J. (Ed.)

   Freshwater mussels are bivalve mollusks that inhabit the substrates of rivers. Fully three-dimensional large eddy simulations are used to investigate flow, turbulence and the capacity of the flow to dislocate an isolated, partially-buried, isolated freshwater mussel placed in a ful-ly-developed incoming turbulent open channel flow. The mussel is aligned with the flow di-rection, which corresponds to normal conditions in rivers containing mussel beds. Its sub-mergence depth is about 60% of the mussel height. The paper focuses on quantifying the ef-fect of the active filtering flow through the incurring and excurring siphons. Simulation re-sults are discussed for two limiting cases with no active filtering and with a filtering flow dis-charge that is close to the maximum value recorded for the investigated freshwater mussel species. It is shown that the active filtering increases the turbulent kinetic energy in the wake and slightly decreases the mean streamwise drag acting on the mussel shell. The paper also discusses the main types of large-scale coherent structures generated by partially-burrowed mussels aligned with the flow, how they are affected by the filtered flow and the effects of these eddies on the bed shear stress, sediment entrainment/deposition phenomena and nutri-ent transport 

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2. Modelling shear stress distribution in ice-covered streams

   https://doi.org/10.1144/SP540-2022-161  

   Koyuncu, Berkay; Le, Trung Bao (April 2023, Geological Society, London, Special Publications)

   Abstract Distribution of bed shear stress is the critical factor in regulating the meandering of single-thread rivers. However, the impact of ice cover on bed shear stress is largely unknown. In this study, we develop a theoretical model of cross-stream momentum balance to examine the distribution of bed shear stresses in ice-covered meandering rivers. To validate the theoretical model, field surveys were carried out in a river reach of the Red River in Fargo, North Dakota. Data monitoring was completed using an Acoustic Doppler Current Profiler to obtain time-averaged velocity profiles. Our theoretical model indicates that an ice covering develops high-shear zones near both the inner and outer banks, which might exacerbate sediment transport and enhance bank erosion. Velocity measurements confirm the results of the proposed model and demonstrate a clear impact of meandering river banks on velocity profiles and secondary flow patterns under ice cover. Based on our results, we hypothesize that ice cover increases turbulent stresses near banks, which in turn lead to the enhancement of the bed shear stress. Our work provides new insights into the impact of ice cover on bed shear stress distribution, which could play an important role in driving sediment-transport processes and the long-term morphodynamic evolution of meandering rivers seasonally covered by ice. 

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3. Identifying potential drivers of distribution patterns of invasive Corbicula fluminea relative to native freshwater mussels (Unionidae) across spatial scales

   https://doi.org/10.1002/ece3.8737  

   Kelley, Taylor E.; Hopper, Garrett W.; Sánchez González, Irene; Bucholz, Jamie R.; Atkinson, Carla L. (March 2022, Ecology and Evolution)

   Abstract This study aimed to identify the importance of ecological factors to distribution patterns of the invasive Clam (Corbicula fluminea) relative to native mussels (family: Unionidae) across seven rivers within the Mobile and Tennessee basins, Southeast United States. We quantitatively surveyed dense, diverse native mussel aggregations across 20 river reaches and estimated mussel density, biomass, and species richness along with density of invasiveC.fluminea(hereafterCorbicula). We measured substrate particle size, velocity, and depth in quadrats where animals were collected. Additionally, we characterized reach scale environmental parameters including seston quantity and quality (% Carbon, % Nitrogen, % Phosphorous), water chemistry (ammonium [], soluble reactive phosphorous [SRP]), and watershed area and land cover. Using model selection, logistic regression, and multivariate analysis, we characterized habitat features and their association to invasiveCorbiculawithin mussel beds. We found thatCorbiculawere more likely to occur and more abundant in quadrats with greater mussel biomass, larger substrate size, faster water velocity, and shallower water depth. At the reach scale,Corbiculadensities increased where particle sizes were larger. Mussel richness, density, and biomass increased with watershed area. Water column increased at reaches with more urban land cover. No land cover variables influencedCorbiculapopulations or mussel communities. The strong overlapping distribution ofCorbiculaand mussels support the hypothesis thatCorbiculaare not necessarily limited by habitat factors and may be passengers of change in rivers where mussels have declined due to habitat degradation. WhetherCorbiculais facilitated by mussels or negatively interacts with mussels in these systems remains to be seen. Focused experiments that manipulate patch scale variables would improve our understanding of the role of species interactions (e.g., competition, predation, facilitation) or physical habitat factors in influencing spatial overlap betweenCorbiculaand native mussels. 

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4. Biological modification of seawater chemistry by an ecosystem engineer, the California mussel, Mytilus californianus

   https://doi.org/10.1002/lno.11258  

   Ninokawa, Aaron; Takeshita, Yuichiro; Jellison, Brittany_M; Jurgens, Laura_J; Gaylord, Brian (July 2019, Limnology and Oceanography)

   Abstract Marine habitat‐forming species often play critical roles on rocky shores by ameliorating stressful conditions for associated organisms. Such ecosystem engineers provide structure and shelter, for example, by creating refuges from thermal and desiccation stresses at low tide. Less explored is the potential for habitat formers to alter interstitial seawater chemistry during their submergence. Here, we quantify the capacity for dense assemblages of the California mussel,Mytilus californianus, to change seawater chemistry (dissolved O₂, pH, and total alkalinity) within the interiors of mussel beds at high tide via respiration and calcification. We established a living mussel bed within a laboratory flow tank and measured vertical pH and oxygen gradients within and above the mussel bed over a range of water velocities. We documented decreases of up to 0.1 pH and 25μmol O₂kg⁻¹internal to the bed, along with declines of 100μmol kg⁻¹in alkalinity, when external flows were < 0.05 m s⁻¹. Although California mussels often live in habitats subjected to much faster velocities, sizeable populations also inhabit bays and estuaries where such moderate flow speeds can occur > 95% of the time. Reductions in pH and O₂inside mussel beds may negatively impact resident organisms and exacerbate parallel human‐induced perturbations to ocean chemistry while potentially selecting for improved tolerance to altered chemistry conditions. 

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5. Particle Resolved DNS Study of Turbulence Effects on Hyporheic Mixing in Randomly Packed Sediment Beds

   Karra, S.; Apte, SV; He, X; and Scheibe, T. (July 2022, 12th International Symposium on Turbulence and Shear Flow Phenomena (TSFP12), Osaka, Japan, July 19--22, 2022)

   Pore-resolved direct numerical simulations (DNS) are used to investigate the interactions between stream-water flow turbulence and groundwater flow through a porous sediment bed in the hyporheic zone. Two permeability Reynolds numbers (2.56 and 5.17), representative of aquatic systems and representing ratio of permeability to viscous length scales, were simulated to understand its influence on the momentum exchange at the sediment-water interface (SWI). A doubleaveraging methodology is used to compute the Reynolds stresses, form-induced stresses, and pressure fluctuations. It is observed that both shear layer and turbulent shear stress penetration increases with ReK. Reynolds and form-induced bed-normal stresses increase with ReK. The peak values of the form-induced stresses for the lower (2.56) and higher (5.17) ReK happen within the top layer of the sediment bed. The sum of turbulent and form-induced pressure fluctuations, analyzed at their respective zero-displacement planes, are statistically similar and can be well approximated by a t location-scale distribution fit providing with a model that could potentially be used to impose boundary conditions at the SWI in reach scale simulations. 

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