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UBC Theses and Dissertations

Impact of wind and river flow on the timing of the Rivers Inlet spring phytoplankton bloom Wolfe, Megan Amelia


The primary objective of this masters study is to develop an understanding of the physical processes driving the timing of the spring phytoplankton bloom in Rivers Inlet. The spring bloom is initiated as light limitation is lifted causing an increase in growth which overcomes loses due to grazing and advection. The bloom is terminated by nitrate exhaustion. The physical system can impact the spring bloom through variations of winds, cloud coverage, and river input. Strong winds showed two effects. First, strong winds increased the mixing layer depth which decreased the amount of light available for phytoplankton, thus delaying the timing of the spring bloom. Second, large outflow winds caused flushing events to occur resulting in rapid horizontal advection removing the plankton population from the area. River discharge has two opposite effects on the timing of the spring bloom. High river discharge causes the water column to stratify, reducing the mixing layer depth which provides more light available for growth and results in an earlier bloom. High discharge will also result in higher upwelling advection leading to a larger advective loss term for phytoplankton, delaying the bloom. Changes in cloud coverage will directly affect the incoming solar radiation and the light available for photosynthesis. A coupled bio-physical model is used to explore the driving forces involved in the timing of the spring phytoplankton bloom in Rivers Inlet, British Columbia, Canada. The primary control on the timing of the spring bloom in Rivers Inlet is wind speed and direction. Secondary control on the timing is due to freshwater flow; high river discharge delays the bloom in Rivers Inlet. Single outflow wind events can result in a 7 day delay in the bloom timing. The shift in bloom timing resulting from multiple outflow wind events is greater than the sum of the individual wind events. Implications of flushing events in fjords along the British Columbia coastline are also discussed.

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