A Model Oxygen Minimum Zone
Saanich Inlet is a seasonally anoxic fjord on the coast of Vancouver Island British Columbia that we visit at monthly time intervals to observe changes in microbial community structure and function along defined redox gradients with an eye toward predicting ecological and biogeochemical responses to ocean deoxygenation.
Ecosystem Type: Aquatic
Location: SI03 (48°35.30N, 123°30.22W)
Saanich Inlet opens to the Strait of Georgia (SoG) on the southeast coast of Vancouver Island, British Columbia. It is approximately 24 kilometers long with a maximal basin depth of 234 meters and receives limited freshwater input from the surrounding watershed. A shallow glacial entrance sill 75 meters deep restricts circulation within interior and basin waters for most of the year. During spring and summer months, restricted circulation combined with high levels of primary productivity in surface waters leads to oxygen loss with concomitant water column stratification indicated by accumulation of methane, ammonia and hydrogen sulfide. In late summer and fall, oxygenated nutrient-rich ocean waters upwelling through the SoG cascade into the inlet shoaling anoxic bottom waters upward and transforming the redox chemistry of the water column. This process is stable on decadal time scales exhibiting a relatively narrow deviation in the depth distribution of the oxycline at different times of the year. The recurring seasonal development of water column anoxia followed by deep-water renewal enables spatiotemporal profiling of microbial community structure and function across a wide range of water column redox states.
Monitoring efforts in Saanich Inlet are informed by an extensive archive of time-series measurements spanning more than five decades and important process studies focused on trace metal cycling, methane-oxidation, denitrification, ammonia-oxidation, chemoautotrophic carbon fixation, and microbial community structure and function. Sampling and data collection are facilitated by close proximity to shore-based and marine assets including the Department of Fisheries and Oceans (DFO) Institute for Ocean Sciences (IOS) and the Victoria Experimental Network Under the Sea (VENUS) cabled observatory.
For more information on the time series and access to archival data please consult the following sources (PMID: 29087371, PMID: 29087370, and PMID: 29087368). Essential primary publications related to coupled biogeochemical cycling in Saanich Inlet include (PMID: 29142241, PMID: 27655888, PMID: 25053816, and PMID: 19900896).