Variability in Diel Vertical Migration of Zooplankton and Physical Properties in Saanich Inlet, British Columbia

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dc.contributor.authorSato, Mei
dc.contributor.supervisorDower, John F.
dc.contributor.supervisorKunze, Eric
dc.date.accessioned2013-05-23T22:51:36Z
dc.date.available2013-05-23T22:51:36Z
dc.date.copyright2013en_US
dc.date.issued2013-05-23
dc.degree.departmentSchool of Earth and Ocean Sciencesen_US
dc.degree.levelDoctor of Philosophy Ph.D.en_US
dc.description.abstractIn Saanich Inlet, a fjord located in southern Vancouver Island, British Columbia, dense aggregations of euphausiids exhibit diel vertical migration behavior and their capability of generating turbulence has been suggested. Despite decades of research on diel vertical migration of zooplankton, its variability has not been well studied. In addition, the physical oceanographic environment in Saanich Inlet has not been thoroughly quantified, which raises the possibility of previously observed turbulent bursts of O(10^-5 – 10^-4 W kg^-1) having physical (rather than biological) origin. This work characterizes variability of diel vertical migration behavior using a moored 200-kHz echosounder, complemented by plankton sampling. Physical properties such as barotropic, baroclinic and turbulent signals are described, and the relationship between turbulence and internal waves/scattering layer examined. A two-year high-resolution biacoustic time-series provided by the Victoria Experimental Network Under the Sea (VENUS) cabled observatory allowed quantification of the seasonal variability in migration timing of euphausiids. During spring – fall, early dusk ascent and late dawn descent relative to civil twilight occur. During winter, late dusk ascent and early dawn descent occur. Factors regulating the seasonal changes in migration timing are light availability at the daytime depth of the scattering layers, and size-dependent visual predation risk of euphausiids. Instead of the traditional view of diel vertical migration timing correlated solely with civil twilight, euphausiids also adapt their migration timing to accommodate changes in environmental cues as well as their growth. The pre-spawning period (February – April) is an exception to this seasonal pattern, likely due to the higher energy demands for reproduction. Turbulence and internal waves in Saanich Inlet are characterized based on a one-month mooring deployment. Average dissipation rates are nearly an order of magnitude larger than previously reported values and higher dissipation rates of O(10^-7 – 10^-6 W kg^-1) are occasionally observed. A weak correlation is observed between turbulent dissipation rates and baroclinic velocity/shear. To examine the possibility of biological generation of turbulence, an echosounder at the VENUS cabled observatory is used to simultaneously measure the intensity of the euphausiid scattering layer and its vertical position. Turbulent bursts of the sort previously reported are not observed, and no relation between diel vertical migration and turbulent dissipation rates is found. Physical forcing at the main channel remains as a possible cause of the turbulent bursts.en_US
dc.description.proquestcode0416en_US
dc.description.proquestcode0415en_US
dc.description.scholarlevelGraduateen_US
dc.identifier.bibliographicCitationSato, Mei, et al. (2013) Second-order seasonal variability in diel vertical migration timing of euphausiids in a coastal inlet. Marine Ecology Progress Series 480: 39-56.en_US
dc.identifier.urihttp://hdl.handle.net/1828/4630
dc.languageEnglisheng
dc.language.isoenen_US
dc.rights.tempAvailable to the World Wide Weben_US
dc.subjecteuphausiidsen_US
dc.subjecttime-seriesen_US
dc.subjectdiel vertical migrationen_US
dc.subjectturbulenceen_US
dc.subjectvariabilityen_US
dc.subjectVENUS cabled observatoryen_US
dc.subjectinternal wavesen_US
dc.subjectcurrentsen_US
dc.subjectSaanich Inleten_US
dc.subjectechosounderen_US
dc.subjectzooplanktonen_US
dc.titleVariability in Diel Vertical Migration of Zooplankton and Physical Properties in Saanich Inlet, British Columbiaen_US
dc.typeThesisen_US

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