| Summary: | Zooplankton play a key role in the functioning of marine ecosystems by transferring energy from phytoplankton to higher trophic levels. Additionally, because of their short generation times and ability to respond rapidly to oceanographic conditions, they have been used as indicators of ecosystem health. Despite their use as ecosystem indicators, there are still critical knowledge gaps in our understanding of zooplankton communities. This includes links between zooplankton biodiversity and ecosystem functions, such as productivity and energy transfer. Difficulties making empirical measurements of ecosystem functions has also created a barrier in addressing these gaps. Lastly, functional role assessments of zooplankton communities can give more insight into the ecological roles of zooplankton species/groups, how they affect ecosystem function, and how community roles may reorganize under climate change scenarios. Chapter 1 introduces zooplankton as crucial to the functioning of marine ecosystems and as key ecological indicators. It also discusses measures of ecosystem function and biodiversity, and drivers of variation in zooplankton communities. Chapter 1 also outlines the objectives of this thesis and describes the regional oceanographic setting of the subarctic northeast Pacific in the context of those objectives. Chapter 2 applies a functional traits-based approach to a 35-year time series of mesozooplankton biomass on the southern shelf along the west coast of Vancouver Island, Canada. Eight functional groups were identified using a functional-trait similarity approach from which biomass anomaly time series for each group were calculated. Generalized additive modeling (GAM) was used to identify drivers of functional group biomass anomaly variability. GAM results found that the key drivers were a local sea surface temperature, the Southern Oscillation Index (SOI), the Pacific Decadal Oscillation (PDO), as well as the North Pacific Gyre Oscillation (NPGO). Functional group biomass anomalies for gelatinous ...
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