No description available.

Marine pollution resulting from oil spillage has received much attention mostly due to the damaging effects it has on fisheries and aquacultures. One component of oil that is widely studied due to its toxic and carcinogenic properties is the polycyclic aromatic hydrocarbons. The physical and chemical properties of these compounds control their distribution into the various phases of the environment. The rates of elimination of these compounds from impacted organisms were investigated in laboratory and field experiments using selected marine organisms (Mytilus edulis and Salmo salar). The elimination of individual PAH compounds followed first order kinetics. Elimination rate varied among compounds and generally decreased with increase in molecular weight and degree of alkylation. Elimination rate constants (k2) and biological half-lives (t1/2) evaluated from chronically exposed mussels (collected from Aberdeen harbour) in separate laboratory and field studies were comparable but differed from those evaluated from acutely exposed mussels. Shorter t1/2 were obtained from acutely exposed mussels. The t1/2 ranged between 0.5- 22 d (acute exposure) and 3.8- 31.5 d (chronic exposure).The longer apparent t1/2 calculated for the chronically impacted mussels was attributed to the retention of the compounds in a stable compartment due to long period of exposure that limited exchange with the surrounding water. Contrary to expectation, t1/2 for similar compounds was higher in salmon than in mussels. The reason for this was unknown but attributed to the route of elimination. A good correlation (r2 > 0.72) was found between PAHs tissue concentration and taint intensity in salmon. Comparison of the results from this study with literature data showed that tank water replacement time and exposure duration affects rate of PAHs elimination. The data generated in this study and some of the reviewed studies will find application in different oil spill scenarios. The usefulness and limitations of the n-alkanes profile, PAH distribution and concentration ratios, and specific biomarker ratios from organisms in oil spill source identification was also demonstrated.

Degradation of water quality, introduction of dreissenid mussels (notably <i>Dreissena polymorpha</i>) and depletion of oxygen concentrations in the hypolimnion in Lake Simcoe, Ontario prompted a study of phytoplankton primary production to inform efforts to improve the lake conditions. The characterization of algal production is critical since, as primary producers, their biomass is positively correlated with production at higher trophic levels in pelagic food webs and oxygen levels. This study was conducted from August 2010 to August 2011, including the winter season (Dec-Mar). Temporally, the lake displayed a unimodal pattern with late summer to fall production maxima. For all seasons considered, the pelagic daily areal primary production (P_int) was lower in the nearshore than offshore, consistent with the nearshore shunt hypothesis that mussels should be able to deplete phytoplankton more effectively in the nearshore. The sensitivity analysis revealed that chl a and the photosynthetic parameter P^B_max were the most influential variables for explaining such spatial differences. The size distribution of chl a and production varied where both netplankton (>20µm) and nanoplankton (2-20µm) were greatest in fall and picoplankton (<2µm) was highest in summer and early fall. A large chl a peak of nanoplankton was also found in late-winter (Mar) at offshore stations. The seasonal areal primary production (SAPP; May-Oct) and chl a:TP were significantly lower nearshore than offshore, consistent with grazing impacts from the large nearshore dreissenid mussel community. The lake as a whole is quite productive comparable to other large lakes with comparable total P concentrations and dreissenid mussel populations. The latter part of the study showed that the deep chlorophyll layer (DCL) was not as frequent as expected and was detected only 28% of time during late-spring to summer when the lake was thermally stratified (Aug-Sept 2010 and May-Aug 2011). The percent dissolved oxygen (%) did not show any indications of elevated primary production in the DCL although the production estimates suggested that there is a substantial (an average of 55%) amount of primary production occurring below thermocline when a DCL exists. Whether or not the DCL has potential to nourish the benthic filterers (dreissenids) and has ecological significance in the lake remains unclear. Overall, the factors that control phytoplankton primary production in Lake Simcoe seem to operate somewhat differently from other large lakes and further investigation is needed to elucidate them. The analysis of primary production and biomass has improved knowledge of non-summer production and can provide guidance to site-specific P and oxygen remediation.

Thesis (M.S.)--University of North Carolina at Wilmington, 2003.

Thesis (Ph. D.)--University of California, San Diego, 1998. / Includes bibliographical references (p. 197-209).

The black-ribbed mussel, Septifer virgatus, is a northern species which forms dominant bands in the mid-low levels of exposed rocky shores along the Northwest Pacific coast. S. virgatus is thought to reach its southern distributional limits just south of Hong Kong. In Hong Kong, mass mortalities of S. virgatus were recorded with the onset of the hot and wet season, with mussel cover decreasing at the upper limit of the mussel bed at Shek O from 82 % (~1746 ind m-2) in May to 9 % (~ 38 ind m-2) in August 2012. Elevated temperatures played an important role in driving physiological responses of the mussel, including heart rate, oxygen consumption and mantle water and haemolymph osmotic concentrations. The upper thermal limit in water (36 °C, as indicated by the Arrhenius breakpoint temperature, ABT), was unlikely to be reached by local seawater, but the ABT in air (~ 41 °C) was often lower than rock temperatures on Hong Kong shores, suggesting S. virgatus is living at its thermal limit. When immersed, both heart rates and oxygen consumption increased from 25 – 35 °C and dropped beyond 35 °C; whilst in air, haemolymph and mantle water osmolalities increased with duration (0 vs 6 hrs) and temperature (30 vs 40 °C) and 60 % of individuals died at 40 °C after 6 hours. Mortality of S. virgatus is, therefore, linked to the high temperatures and desiccation stress experienced on the shore, which are likely to impose high energetic costs. To better understand the performance of S. virgatus under natural conditions, and the energetic implications of thermal stress on its survival and fitness and hence potential distribution, a Dynamic Energy Budget (DEB) model was constructed. The model had a high goodness of fit. Mussels were predicted to live 5 years, and their main growth and energy reserves were derived from high assimilation during the hot and wet season when food was most abundant, while another slower growth period and reproduction occurred during the cool and dry season. Energy stored in the reserve during growth periods was likely to be allocated to combat thermal stress during the hot and wet season and reproduction during the cool and dry season. The DEB model was used to investigate the energy allocation strategies of S. virgatus under the most conservative and extreme scenarios associated with climate change as projected by the IPCC. The model predicted that reproductive events throughout the mussels’ life-span would be reduced by 30 – 70 %, despite an increase (18 – 470 %) in number of eggs per event. This reduction in the number of reproductive events might not be able to sustain local populations due to the high annual mortality. Such a decrease in performance and fitness, associated with not being able to reach the energy threshold necessary for somatic maintenance, suggests that S. virgatus may be limited to living lower on the shore, where conditions and duration of exposure are more benign, and ultimately experience a northwards range shift as environmental temperatures increase. / published_or_final_version / Biological Sciences / Master / Master of Philosophy

published_or_final_version / Zoology / Master / Master of Philosophy

published_or_final_version / Zoology / Doctoral / Doctor of Philosophy

No description available.

Degradation of water quality, introduction of dreissenid mussels (notably <i>Dreissena polymorpha</i>) and depletion of oxygen concentrations in the hypolimnion in Lake Simcoe, Ontario prompted a study of phytoplankton primary production to inform efforts to improve the lake conditions. The characterization of algal production is critical since, as primary producers, their biomass is positively correlated with production at higher trophic levels in pelagic food webs and oxygen levels. This study was conducted from August 2010 to August 2011, including the winter season (Dec-Mar). Temporally, the lake displayed a unimodal pattern with late summer to fall production maxima. For all seasons considered, the pelagic daily areal primary production (P_int) was lower in the nearshore than offshore, consistent with the nearshore shunt hypothesis that mussels should be able to deplete phytoplankton more effectively in the nearshore. The sensitivity analysis revealed that chl a and the photosynthetic parameter P^B_max were the most influential variables for explaining such spatial differences. The size distribution of chl a and production varied where both netplankton (>20µm) and nanoplankton (2-20µm) were greatest in fall and picoplankton (<2µm) was highest in summer and early fall. A large chl a peak of nanoplankton was also found in late-winter (Mar) at offshore stations. The seasonal areal primary production (SAPP; May-Oct) and chl a:TP were significantly lower nearshore than offshore, consistent with grazing impacts from the large nearshore dreissenid mussel community. The lake as a whole is quite productive comparable to other large lakes with comparable total P concentrations and dreissenid mussel populations. The latter part of the study showed that the deep chlorophyll layer (DCL) was not as frequent as expected and was detected only 28% of time during late-spring to summer when the lake was thermally stratified (Aug-Sept 2010 and May-Aug 2011). The percent dissolved oxygen (%) did not show any indications of elevated primary production in the DCL although the production estimates suggested that there is a substantial (an average of 55%) amount of primary production occurring below thermocline when a DCL exists. Whether or not the DCL has potential to nourish the benthic filterers (dreissenids) and has ecological significance in the lake remains unclear. Overall, the factors that control phytoplankton primary production in Lake Simcoe seem to operate somewhat differently from other large lakes and further investigation is needed to elucidate them. The analysis of primary production and biomass has improved knowledge of non-summer production and can provide guidance to site-specific P and oxygen remediation.