College of Science and Engineering
Permanent URI for this collectionhttps://hdl.handle.net/10877/17053
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Browsing College of Science and Engineering by Author "Ackerman, Josef Daniel"
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Item Dispersion of Freshwater Mussel Larvae in a Lowland River(American Society of Limnology and Oceanography, 2010-01) Schwalb, Astrid Nadine; Garvie, Marcus; Ackerman, Josef DanielWe examined the dispersal of larvae (glochidia) of a common unionid mussel species, Actinonaias ligamentina, which need to attach to a host fish in order to develop into juveniles, in a lowland river (Sydenham River, Ontario, Canada). Generally, the decline in the number of glochidia captured with distance from release was best described by an inverse power function. The highest proportion was found in the first net 4 m downstream (range 0.1–3.6%), but a small proportion of glochidia was captured 96 m downstream (0–0.03%). This indicates that infestation of host fish may occur several tens to hundreds of meters downstream of the adults’ location, even at relatively low flow conditions (mean velocity, 15 cm s-1). Dispersal distances increased with velocity, but the number of glochidia sampled at a given location can vary considerably due to stochastic effects of turbulence, especially at shorter distances. Individual trials could, therefore, deviate considerably from the predictions of an existing turbulent transport model (local exchange model), but overall there was a good correlation between measured data and model prediction. However, model predictions were quantitatively much higher than measured values (i.e., 50 fold in some cases), which could be in part due to several simplifying assumptions of the model.Item Settling Velocities of Juvenile Lampsilini Mussels (Mollusca:Unionidae): The Influence of Behavior(North American Benthological Society, 2011-01) Schwalb, Astrid Nadine; Ackerman, Josef DanielJuvenile unionid mussels disperse in the water column after detachment from their host fish. The settling velocity (ws) of juvenile mussels is an important component of their dispersion in the water column but has not been measured for unionid mussels. The goal of our study was to measure the ws of juvenile mussels in the laboratory and to examine how ws varied within and among related species. The ws of Actinonaias ligamentina and Ptychobranchus fasciolaris were significantly lower (2.4 6 0.1 mm/s vs 2.5 6 0.1 mm/s, respectively) than those of the larger-sized Lampsilis fasciola and Epioblasma triquetra (4.2 6 0.2 mm/s vs 4.6 6 0.2 mm/s, respectively). Overall, ws increased with juvenile size, but considerable variation (,103) was found within species. Observations indicated that foot movement of juvenile mussels was responsible for reductions in ws, and this behavior may provide a potential mechanism for habitat selection at small-spatial scales. Observed ws differed considerably from ws predicted from Stokes law using empirically determined shell size and density (r = 1.22 6 0.003 g/cm3 for A. ligamentina), which indicates some of the limitations in predicting ws from size measurements.Item The Effect of Settling Velocity on the Transport of Mussel Larvae in a Cobble-bed River: Water Column and Near-bed Turbulence(Association for the Sciences of Limnology and Oceanography, 2012-01) Schwalb, Astrid Nadine; Morris, Todd James; Ackerman, Josef DanielSimple transport models predict that the distance organisms drift downstream in rivers is determined by their settling velocity (ws), the release height (zr), and the stream velocity (U). Unfortunately, empirical evidence is lacking on whether and how factors such as ws affect mussel larvae dispersion in rivers under natural turbulent conditions. The main goal of this study was to examine how U and ws affect the transport of freshwater unionid mussel larvae (glochidia) in a turbulent reach of the Grand River, Ontario, Canada. Glochidia of Actinonaias ligamentina and Lampsilis fasciola, which had a 2.5-fold difference in their ws (0.9 – 0.02 [mean – SE] and 2.2 – 0.02mms-1, respectively), were released and captured in a series of drift nets downstream. Larval dispersion in rivers appeared to be strongly affected by hydrodynamic conditions. The results indicated that glochidia are dispersed more rapidly with increased U. This is likely due to increased turbulence and lateral and vertical mixing, which were consistent with the predictions of a 3-dimensional advection–diffusion model. The decline of glochidia with distance was well described with an inverse power function, but only on days when the average U measured at 40% water depth was .40 cm s-1. In contrast to the predictions of simple transport models, the observed downstream transport did not differ significantly between glochidia with different ws. Further studies are needed to better understand the effect of differences in ws and zr under different hydrodynamic conditions, which may also be important for other dispersal phenomena.