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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Influence of hydrographic properties in Saanich Inlet on ontogenetic migration and retainment of the calanoid copepod Neocalanus plumchrus

French, Shirley E. January 1988 (has links)
During some years Neocalanus plumchrus overwinters in Saanich Inlet while in other years they are absent from the fjord (Harrison et al., 1983). The cause of this variation is not known but the annual development of anoxic conditions followed by an intrusion of dense, oxygenated water, was suspected to influence their distribution and abundance. Vertical and horizontal haul samples collected from Saanich Inlet indicated the overwintering population in 1985 (September 1985 to March 1986) was sparse; in September 1986 the population of N. plumchrus was comparably low. In the spring and summer, N. plumchrus is introduced from the Strait of Georgia and Juan de Fuca Strait, and in some years may arise from reproduction within the inlet. So few adults were collected at the three stations in Saanich Inlet in January-March 1986 (<0.20 m⁻³) that their potential contribution to the spring population was considered negligible. Decline in the overwintering population in September 1985 and 1986 appears to be correlated with the occurrence of an extensive deep water renewal. The distribution of N. plumchrus during early stages of their deep water migration (June to August), is influenced by the low oxygen concentrations in the bottom of the inlet (i.e. 0.10-0.30 mL L⁻¹). During the renewal, copepods occurred above the oxygen minimum (75 m) possibly due to their displacement or their avoidance of the low oxygen zone. Subsequently, they were exposed to tidal transport out of the inlet and perhaps to increased predation. On two occasions in which N. plumchrus was present during the winter in Saanich Inlet (1969 & 1974), a high volume of dense water intruded, disrupting the copepod layer during the mixing of the two water masses. Even though a greater volume of water left the inlet some of the copepods could have remained in the water, below sill depth. Neocalanus plumchrus successfully overwinters and reproduces in Sechelt Inlet which is well-oxygenated but has a very shallow sill (15 m) that 'locks' the copepods into the inlet. The fifth copepodite stages also occupy deeper depths in Sechelt Inlet than in Saanich Inlet, even though the bottom depths are comparable. In low oxygen tolerance experiments many factors such as the period of captivity, and the region of origin (i.e. Saanich Inlet versus the Strait of Georgia) caused variable results. Although the minimum oxygen level tolerable during their migration could not be determined, N. plumchrus tolerated levels as low as 0.56 mL L⁻¹ (12% mortality). Sediment trap samples indicate that a massive die off could not account for the loss of N. plumchrus from Saanich Inlet. / Science, Faculty of / Zoology, Department of / Graduate
2

Comparative morphology of sibling species of Metridia (Copepoda:Calanoida), M. lucens, M. pacifica and a species indeterminata from Indian Arm, British Columbia

Thorp, Arthur Chadwick January 1980 (has links)
Metridia lucens and M. pacifica previously have been differentiated primarily by the structure of the male fifth legs. lucens originally was described to have one large spine on the inner margin of the fourth segment and M. pacifica to have two spines, one each on the third and fourth joints. Some authors have reported M. lucens with two so-called spines on the same segment and M. pacifica also with two such spines but located together on the fourth segment. This led to M. pacifica being questioned as a species by certain authors who claimed it synonymous with M. lucens. In the present study, M. lucens from the Northwestern Atlantic is compared with M. pacifica from the Northeastern Pacific and differences in size and structure are evident to separate them. The fifth pair of legs on adult males and females were examined and findings indicated errors in the original descriptions of both species. Another Metridia population, found in the coastal waters of British Columbia, was compared with the described species. It was found to be similar to M. lucens and could be, in part, the reason for the past confusion between the Atlantic and Pacific species. / Science, Faculty of / Zoology, Department of / Graduate
3

Seasonal changes in hydrographic and chemical properties of Indian Arm and their effect on the calanoid copepod Euchaeta japonica

Whitfield, Paul Harold January 1974 (has links)
This study examines seasonal changes in the relationship between a test organism and changes in the hydrographic and chemical properties of Indian Arm, a coastal fjord. There is a close relationship between changes in the hydrographic properties of the water and changes in the metal complexing ability of water in the inlet, as determined with the test organism. The relationship between the organism and the availability of metals changes with time; the complexing ability of natural water increases at the time of the major intrusion of water from the Strait of Georgia into Indian Arm, and then decreases. The addition of a variety of metals under experimental conditions affects the relationship between the organism and the complexing ability of the water. Additional studies examine the effect of material extracted from sediment samples on the toxic effect of copper enrichment. The ability of the extracted material to reduce the toxic effect changes and is related to the seasonal productivity in the surface waters of the inlet. / Science, Faculty of / Zoology, Department of / Graduate

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