Using SCUBA and an in situ method of quantifying substrate characteristics, I describe patterns of zebra mussel (Dreissena polymorpha) distribution along the St. Lawrence and Hudson Rivers and in Oneida Lake, New York, and develop empirical models for their abundance. Calcium-poor waters originating from rivers draining the Canadian Shield resulted in a lack of zebra mussel along the north shore of the St. Lawrence River east of Montreal until Portneuf despite an abundance of suitable substrate. Calcium concentrations of 15 mg/L or less were found to limit the distribution of zebra mussel. The entire south shore from Cornwall, Ontario to Ile d'Orleans, Quebec was colonized by zebra mussel wherever suitable substrate was found. In the Hudson River, along the south shore of the St. Lawrence River and in Oneida Lake variability in density was primarily related to substrate type which explained between 38% and 91% of the variance. Other factors such as Secchi depth, calcium concentration of the water, the presence of crayfish, native unionid abundance and the maximum width of the river at the site increased the amount of explained variance across the different systems. The influence of substrate type on zebra mussel density and the predictions of the model were also tested using data from the literature, where substrate type explained 75% of the variability in density. The scatter of the literature data above the predictions of the empirical model suggests that North American zebra mussel populations may continue to grow before reaching equilibrium levels. While water chemistry parameters may be useful predictors of the presence or absence of zebra mussel in a given water body, physical factors play a far greater role in determining local abundance.

Thesis (M.S.)--Ohio University, November, 1997. / Title from PDF t.p.

Thesis (M.S.)--Virginia Polytechnic Institute and State University, 2003. / Title from PDF t.p. (viewed on Dec. 9, 2005). Vita. Includes bibliographical references.

Thesis (Ph. D.)--Virginia Polytechnic Institute and State University, 1993. / Vita. Includes bibliographical references (leaves 152-169).

Thesis (Ph.D.)--University of Waikato, 2006. / Includes bibliographical references (leaves 135-150)

Continuous or semi-continuous reproduction is the norm in deep-sea animals, with exceptions explained by seasonal pulses of surface-derived phytodetritus. Chemosynthesis-based ecosystems such as cold seeps have an independent nutritional supply and are often thought of as decoupled from surface productivity. This thesis explores reproductive patterns of four bathymodiolin mussel species from 14 cold seeps (320 to 3300 m depth) in the Gulf of Mexico (2014) and the northwestern Atlantic (2015). Using paraffin histology, I determined maturity stages for male and oocyte sizes for female mussels. All species at all sites reproduced periodically and synchronously, with geographic synchrony among sites. This suggests that mussels rely on a site-independent cue such as seasonal phytodetrital flux to synchronize reproduction, providing evidence for a stronger coupling between surface productivity and chemosynthesis-based fauna than previously expected. Mature oocytes were of similar size for all species at all depths, suggesting that egg size is phylogenetically constrained.

The principal aim of this study was to establish the biological and environmental parameters governing the successful and sustainable cultivation of mussels in Saldanha Bay. The environmental study investigated seston, chlorophyll-a and particulate organic matter (POM) levels, water temperature dissolved oxygen and salinity levels in the bay and water flow in and around the rafts. The biological part of the study investigated the efficiency of food extraction, growth rates, mussel condition, fouling and production and yield on a rope, raft and farm scale. Saldanha Bay is well suited for the culture of mussels, particularly Mytilus galloprovincialis and Choromytilus meridionalis. Water temperature and salinity in Saldanha Bay were found to be near optimal for mussel culture. POM and chlorophyll-a levels were found to be high due to primary production resulting from the nutrient rich upwelled water outside Saldanha Bay. The mean levels of chlorophyll-a (8,6μg/l) represent 6%, by mass, of the total POM. On a bay scale the POM remained above the mussels maximum requirements (pseudofaeces threshold) during the study period. Mussels showed a preference for the phytoplankton portion of the POM. Approximately 40% of the chlorophyll-a was extracted from the water by the mussel farm. The efficiency of food extraction increased with mussel age. Rafts with seed mussels younger than 2 months, 3 to 4 months, 5 to 6 months and older than 6 months extracted 32%, 55%, 85% and 92% of the available chlorophyll-a respectively. An increase of rope spacing on the rafts resulted in 37% more chlorophyll-a and 30% more particle volume reaching the lee of the raft. Ambient water currents in the bay show flow rates of up to 22cm per second. However, on entering a raft with a rope spacing of 60cm, the water flow is attenuated by 90%. Increasing the rope spacing to 90cm resulted in a water flow attenuation of 72%. The increase in rope spacing ensures that the mussels in the centre of the raft are feeding on food levels close to, or above, the pseudofaeces level. Mussel growth rate at a rope spacing of 90cm is significantly improved as a result of the increased food delivery. There are other factors, however that effect mussel growth. Growth rates were found to be better in summer than in winter. The reduced winter growth rate is possibly due to competition with the maturing fouling organisms which settle in mid to late summer. Fouling by mussel spat and Ciona intestinalis is seasonal, occurring from December to May. C.intestinalis is prevalent in the centre of the farm and rafts as low energy waters are preferred by this species. Mussel spat settles mainly on the periphery of the farm and the rafts. Competition with fouling organisms reduces growth and increases mortality of the cultured mussels. Results indicate that the present spacing of rafts, (1 raft per hectare) is adequate under existing conditions. Any new farms should maintain batches of 50 rafts with channels between them to ensure water current penetration into the furthest reaches of the farm. Rope spacing on the rafts should be increased to between 60cm and 90cm. Mussel density should be regulated according to mussel size and fouling should be controlled to maintain yields.

No description available.

Laboratory bioassays results suggest that early life stages of freshwater mussels are sensitivity to toxicants. However, toxicological databases for unionids are rather limited because standard test methods are yet developed, and no published studies report endpoints for chronic test that are > 9 days. The primary goals of my thesis research were to assess acute and chronic toxicities of chlorine and mercury to early life stages. Inter- and intra-specific species variability in the tolerances of glochidia was observed during acute laboratory bioassays as endpoints were between 8 - 43 ppb for Hg tests, 1.0 - 2.5 ppm for NaCl tests, and 70 - 260 ppb for chlorine (TRC) tests. Glochidia of several species had equal or greater sensitivities to Hg and NaCl than test organisms commonly used to assess environmental risk (i.e.Ceridaphnia dubia, Daphnia magna, Pimephales promelas), whereas they were far more tolerant to TRC than many species. Twenty-one day chronic test endpoints for juveniles were substantially lower than those calculated during acute bioassays with glochidia. Villosa iris 3-mo old juveniles were found to be quite sensitive to Hg as growth was significantly impaired at 8 ppb Hg. Chronic bioassays with TRC revealed a distinct decrease in susceptibility with increased aged for V. iris (relative sensitivities 3-mo > 6-mo > 12-mo), and that 2-mo old Epioblasma capsaeformis were more sensitive than comparable age classes of V. iris. However, both species were tolerant compared to other aquatic organisms, as the lowest endpoint was 20 ppb TRC. / Master of Science

A flow-through pond at White Sulphur Springs National Fish Hatchery was evaluated as culture environment for juvenile freshwater mussels of Villosa iris and Lampsilis fasciola. Survival did not differ significantly (p = 0.1910) over 93 d for V. iris cultured with silt (mean 49.8% ± SD 14.5) and without (mean 32.9% ± SD 11.7). Survival differed significantly (p <0.0001) between juveniles of V. iris (mean 49.8% ± SD 14.5 at age 93 d) and L. fasciola (mean 6.3% ± SD 4.5 at age 86 d). This may indicate that the pond failed to meet requirements of L. fasciola, or may have resulted from microhabitat variables. Growth did not differ significantly between species (p = 0.1315). Villosa iris reached a mean length of 1.81 mm ± SD 0.67, and L. fasciola 1.78 mm ± SD 0.78. Water quality parameters remained within suitable ranges, and planktonic algal densities were between 2850 - 6892 cells/mL. Survival of V. iris and growth of both species compares favorably to previous culture attempts. Juveniles of V. iris and L. fasciola were exposed to ammonium chloride solutions for 96 h in static renewal conditions at 12°C and 20°C. Calculating LC50 values with the Trimmed Spearman-Karber method, juveniles of L. fasciola (mean 96 h LC50 of 0.26 mg/L NH3-N) were significantly more tolerant of unionized ammonia than juveniles of V. iris (mean 96 h LC50 of 0.11 mg/L NH3-N). The only organisms with reported LC50 values lower than those seen for V. iris juveniles were Ceriodaphnia dubia and Hyella azteca. / Master of Science