Properties of the Water in the Strait of Georgia, British Columbia, and Influencing Factors

Abstract

The temperature, salinity, pH, and concentrations of dissolved oxygen, dissolved nitrates, nitrites, inorganic phosphates, and silicates are shown and discussed. The occurrence of these properties and their seasonal and diurnal cycles are related to the mechanism of tidal exchange, discharge of the Fraser River, weather, and growth of plankton to show the sources of the properties, the sequence of their change, and why, when, where, and how they occur.In the Strait of Georgia the waters are highly stratified. Fresh water from the Fraser River moves persistently seaward, entraining sea water en route. An upper brackish zone is formed in which the constituents occur in cloud-like distribution, and vary with tide and season. Below this is a deep zone where stratification is slight, and the properties are nearly constant throughout the area and the year.In the approaches to the strait the tidal flows are turbulent and mix the waters to homogeneity. Here the highly stratified upper-zone waters became apparent during the ebb flow, and homogeneous waters during the flood.The high concentrations of dissolved phosphates are attributed to the ocean water which intrudes the region in the lower zone. The high concentrations of dissolved silicates are attributed to the Fraser River waters. It is suggested that the supply of dissolved nitrates is the limiting factor in phytoplankton growth.