Thesis (M.S.)--Naval Postgraduate School. / Bibliography: leaves 126-128.

Temperature, salinity, and other, undefined properties of sea water have been suggested as factors acting to limit the distribution of planktonic organisms through the stresses they impose. The aim of this study was to examine experimentally the effects of changes in these properties on the respiration of Euphausia pacifica Hansen. Both immediate and long term effects of changes in these properties were examined. Assessments of the immediate effects of changes in temperature and salinity on the animals' respiratory rate demonstrated that a sharp reduction in respiratory rate could be used as an indication of stress. The results of these same experiments showed that as the values of temperature and salinity approached the limits of tolerance, the effects of stresses from them interact. The long term effects of changes in temperature and salinity were investigated by determining the limits of these factors that were tolerable to specimens from areas in which the characteristic temperatures and salinities of the water were different. Specimens from the water having the greatest range of values of temperature and salinity (coastal) possessed the greatest tolerance to changes in temperature and salinity; specimens from water having the least range of temperature and salinity (oceanic) had the least tolerance. The tolerances to changes in temperature and salinity observed in these experiments indicated that the distribution of E. pacifica in British Columbia coastal waters was not likely to be influenced by changes in temperature and salinity except near the surface, where the salinity may become low and the temperature high or very low. Experiments taking advantage of the interaction between the effects of temperature and salinity were used to establish that other properties of sea water, while undefined, could impose stress on adult E. pacifica. At the same time a method of assessing the effects of changes in undefined properties between sea waters through a comparison of respiratory rates obtained under standard conditions was developed. The results of experiments in which changes in undefined properties of sea waters collected at two depths in each of two locations were examined indicate that these properties appear to be a function of the origin of the particular water. They also indicate that differences between waters in these properties did not affect the distribution of E. pacifica within either of the two areas investigated, namely the Strait of Georgia and Indian Arm. The results did indicate, however, that populations of E. pacifica were present in each of these areas in which inverse reactions to the same set of undefined properties existed. Presumably these result from persistent differences in undefined properties between the waters resident in each of the two areas. / Science, Faculty of / Zoology, Department of / Graduate

Microstructure and acoustic data were collected in Saanich Inlet, British Columbia, and at Ocean Station P in the eastern subarctic North Pacific Ocean with the objective of observing krill-generated turbulence. At Ocean Station P, although a number of species composing the zooplankton community are large enough to generate turbulent flow (Re > 10e3), no turbulence events could be correlated with presence of swimming marine organisms and measurements indicated turbulence generated by shear. Zooplankton densities were likely too low to produce turbulence at the scale of an aggregation and the O(10e-2 m) scattered turbulent signals generated by individuals are difficult to detect in the natural environment. In Saanich Inlet, higher dissipation rates were observed in regions of high acoustic backscattering, suggesting that zooplankton-generated turbulence was occurring. Although presence of zooplankton was often correlated with high dissipation rates, high dissipation rates were frequently observed in the absence of zooplankton, suggesting multiple sources of turbulence. High dissipation rates were observed in the presence of non-migrating zooplankton as much as in the migrating layer. These turbulence events occurred at a scale of more than 1 m as they were positively detected by our dissipation rate estimation technique. This suggests that marine organisms can act together to generate turbulence at scales that can produce diapycnal mixing. Over all time-series collected, dissipation rates in the presence of zooplankton averaged 1.4 x 10e-8 W/kg whereas the average in the absence of zooplankton was 0.7 x 10e-8 W/kg.