Dissolved Oxygen depth profile for Saanich Inlet. The blue region at the bottom of the inlet indicates low concentrations of dissolved oxygen. Maximum sub-bottom depths sampled were 105 and 118 m at the two sites, respectively. From earlier studies, these are known to be related to late fall and winter, early spring, and late spring and summer deposition, respectively. This variability reflects significant changes in amount and seasonal distribution of precipitation and associated erosion rates in nearby watersheds, and in primary productivity in the inlet.
Initial observations suggest variability on decadal and century timescales.
Superimposed on this idealized varve structure are finer scale variations, readily apparent in x-radiography. These sub-millimeter scale laminae record changes in surface productivity, possibly related to tidal cyclicity, and in runoff from the surrounding watersheds. The laminated sequence contains abundant wood and charcoal as well as fish scales, vertebrae and other skeletal material. Charcoal studies will provide a history of forest fire frequency which in turn can be related to local climatic factors and land use practices by aboriginal peoples. Investigations of past fish populations will assist in determining the causes of recent decreases in salmon and herring abundances and will shed light on past species abundances.