Thesis (M.S.) in Oceanography--University of Maine, 2003. / Includes vita. Includes bibliographical references (leaves 55-57).

Thesis (M.S.) in Oceanography--University of Maine, 2003. / Includes vita. Includes bibliographical references (leaves 40-43).

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Biology, 1980. / Supervised by G. Richard Harbison. Vita. Includes bibliographical references (p. 141-153).

Thesis (Ph.D. (Zoology & Entomology)) - Rhodes University, 2007.

No description available.

No description available.

A device, utilising the suction produced by a disposable syringe, was developed to restrain a range of very small organisms in flowing seawater. The technique was developed during an investigation of the swimming response of barnacle nauplii to changes in temperature. The combination of beat frequency and the proportion of time spent active was held constant for B. balanoides and B. hameri but steadily increased with temperature for C. montagui and B. amnhitrite. E. modestus showed an intermediate response. Methods for utilising video-tape recordings and a micro-impedance pneumograph for analysing limb beat activity, were developed during an investigation of the feeding behaviour of nauplii. The feeding mechanism was reappraised and an increase in the volume of water handled by the larvae noted in the presence of food organisms. This increase was shown by E. modestus nauplii in response to dissolved organic substances, indicating that the nauplii could determine when to feed, and what was edible, from the shell of dissolved material surrounding food particles. A quantitative study of the grazing of E. modestus nauplii showed that the ingestion rate of algal cells increased up to concentrations of 150 - 200 cells/ul, then remained steady. Larger algal cells were taken from algal mixtures, in preference to smaller ones. Restraint techniques and video-recordings of free-swimming cypris larvae showed them to be prodigeous swimmers, with considerable control over the direction and magnitude of the thrust produced. The close observation of larvae allowed by the restraint technique enabled mechanical stimulation of particular sense organs. The function of these organs had been interpreted from their structure by previous authors. In some instances, a mechano-receptive function was confirmed, but in others, doubt was cast. Restrained cyprids responded to complex sound fields by swimming less often. A dual mode sound chamber was used to differentiate between sound pressure and displacement, but negative results were obtained. The cyprids did, however, respond to substrate vibrations, at low frequencies, by swimming off the substrate. All the developed techniques were further employed to show that the classical copepod feeding swirls were artefacts. Temora produced'only a posteriorly flowing current for feeding and swimming, when restrained in larger volumes of seawater. The amount of water handled by Temora was also shown to increase when food algae were present.

Gelatinous zooplankton are characterised as different from other planktonic taxa due to the high relative water content of their tissues. This thesis investigates whether elevated somatic water content (expressed here as carbon percentage) has effects on the biology of zooplankton. My approach was to examine this at a range of scales with a variety of approaches, ranging from experiments on individual ephyra larvae of Aurelia aurita, through analysis of a zooplankton time series at the Plymouth L4 station, up to a large scale meta-analysis of zooplankton growth and body composition data. In this meta-analysis, carbon percentage varied continuously across the range of the zooplankton, ranging from 0.01% to 19.02% of wet mass, a difference of over three orders of magnitude. Specific growth rate (g, d-1) was negatively related to carbon percentage, both across the full range of zooplankton species, and within the subset of taxa traditionally classified as gelatinous. The addition of carbon percentage to models of zooplankton growth rate based on carbon mass alone doubled explanatory power. I present an empirical equation of maximum (food saturated) zooplankton growth that incorporates carbon mass and carbon as a percentage of wet mass. Applying this equation to a natural assemblage near Plymouth yielded sometimes double the secondary production, as compared to a simpler model based on crustacean growth. Both interspecifically and intraspecifically, carbon percentage was negatively related to carbon mass; more gelatinous taxa tended to have higher carbon masses. During the early development of Aurelia aurita ephyrae, carbon percentage was found to decrease from 2.36% (an intermediate value between crustaceans and classical gelatinous zooplankton) down to 0.1%, the adult value for Aurelia aurita. Juvenile forms of gelatinous taxa are often poorly sampled and their intermediate carbon percentages may help to form a continuum between those of crustaceans and adult cnidarians and ctenophores. As ingestion in the ephyrae was related to their diameter, models suggest that this dilution resulted in an increase in carbon-specific ingestion rate by an estimated 28% relative to an ephyra that did not dilute through development. At the species level, carbon percentage was negatively related to indices of temporal variation in numerical density but not related to rate of population increase. A wide variety of zooplanktonic taxa of different carbon percentages were found to increase in population at a rate that could be considered as forming a bloom. Likewise many gelatinous taxa at L4 did not form blooms. Thus the frequent reference to “jellyfish blooms” reflects, in part, the fact that unlike the other zooplankters that regularly reach even higher carbon concentrations, gelatinous taxa are simply more noticeable to the eye when at these concentrations. Calculating the carbon percentage of whole assemblages could be useful for investigating the influence of environmental parameters on zooplankton. Taken together, these results demonstrate the benefits of explicitly recognising the decoupling of metabolic and ecological body size seen in the gelatinous zooplankton.

Annual and seasonal changes in distribution and abundance of six species of macro-zooplankton (Cyclops bicuspidatus thomasi, Diaptomus ashlandi, Daphnia galeata mendotae, Diaph- anosoma leuchtenbergianum, Bosmina coregoni, and Mysxs relicta.) twgre studied in Kootenay Lake, a body of water extending over 105 km in southeastern British Columbia. Differences between two years, 1949 and 1964, were examined as well as changes in midsummer distribution and abundance between three consecutive years (1964 to 1966). Seasonal changes during one year and within a summer were also noted as well as diel changes in distribution and abundance. A large increase in zooplankton abundance occurred during the fifteen year period from 1949 to 1964, and this was attributed to an increased inflow of primary nutrients from a major tributary at the south end of the lake. A change in species composition, formerly dominated by Daphnia but now by Diaphanosoma, was related with eutrophication. Changes in food availability due to eutoophication, competition for food with Mysis relicta, and heavy predation by kokanee (Oncorhynchus nerka), were examined as factors possibly responsible for changes in the spatial distribution of Daphnia since 1949. Differences in the midsummer zooplankton distribution and abundance between three consecutive years (1964 to 1966) were minor, suggesting that the changes noted between 1949 and 1964 were attributable to large changes in limnological conditions and not merely the result of annual fluctuations. Examination of seasonal trends in zooplankton distribution and abundance indicated that zooplankton, with the exception of Mysis relicta, were most abundant during the summer. Mysids were most abundant in May when the young mysids were released from the brood pouch. Spatial differences in summer zooplankton abundance was examined in relation to wind-driven currents, and food availability. Spatial differences during the rest of the year were minor, possibly a result of similar limnological conditions at all stations then. Abundance of Mysis relicta was greatest in the north arm of the lake, whereas all other species were most abundant in the central area of the lake. Changes that occurred within the summer were largely due to high turbidity in the south arm during June and July. Diel changes in the vertical distribution of zooplankton, with the exception of Mysis relicta, were not detected. / Science, Faculty of / Zoology, Department of / Graduate

Preliminary investigations of Saanich Inlet, Vancouver Island, British Columbia, indicated that there was a stratification in the depth of occurrence, during daytime, of the euphausiid Euphausia pacifica and the amphipods Cyphocaris challengeri and Orchomenella pinguis. The presence of an oxycline and a gradient in the carbon dioxide concentration suggested that the stratification was associated with these environmental factors. A programme was conducted between July 1962 and June 1963 to determine whether the stratification was a persistent phenomenon and whether physical and chemical characteristics of the water were associated with the distribution of the organisms. Clarke-Bumpus plankton samplers were towed above, within, and below the oxycline on seven cruises. The survival of the species was measured above, within, and below the oxycline, for exposures of 1 to 12 hours for Euphausia pacifica and Cyphocaris challengeri and of 9 to 24 hours for Orchomenella pinguis, by lowering specimens in cylinders which were in communication with the environment. Laboratory experiments measured the oxygen consumption of the species when carbon dioxide produced by the organisms in experimental chambers accumulated and when it was absorbed. Stratification was a persistent phenomenon in which Euphausia pacifica occupied the upper position, Orchomenella pinguis the lower position and Cyphocaris challengeri an inter-mediate or upper position in the daytime aggregation of organisms. The position of the aggregation was not influenced by temperature or salinity, but was related to the concentration of oxygen, and carbon dioxide. The field experiments showed that Orchomenella pinguis could tolerate lower oxygen and higher carbon dioxide concentrations for much longer durations of exposure than could the other two species. The laboratory experiments indicated Orchomenella pinguis and Cyphocaris challengeri consumed less oxygen than Euphausia pacifica, but Cyphocaris challengeri was more susceptible to high concentrations of carbon dioxide than the other species. These facts offer partial explanations for the stratification of the species. / Science, Faculty of / Zoology, Department of / Graduate