Page 10 - HydrographyReadMe
P. 10

Mean Conditions in the Strait of

               Georgia



                                                       Mean near-surface conditions for the Strait of Georgia
                                                       since 2015.  This figure summarizes thousands of
                                                       stations, the combined efforts of dozens of people
                                                       over many years.

                                                                              th
                                                       Note in particular the 5  row, which shows the
                                                       seasonal and interannual changes in the the biomass
                                                       of primary producers (phytoplankton) in the Strait, the
                                                       ultimate source of organic material for all animal life
                                                       in the Strait.  Sometime during March/April in each
                                                       year the spring phytoplankton bloom occurs and the
                                                       biomass increases tremendously before exhausting
                                                       the immediately available nutrients. Since this very
                                                       important event sometimes occurs between sampling
                                                       times, or earlier than sampling occurred in some
                                                       years, red markers are show to indicate the bloom
                a) Fraser River inflow b) surface temperature c)
                surface salinity d) surface dissolved oxygen e)   time as estimated from continuous measurements of
                Chlorophyll biomass (vertical bars show spring   near-surface Chlorophyll from BC ferries.
                bloom timing from other programs) f) surface
                nitrate g) surface silicate h) surface phosphate




                                                       This figure shows the anomalies around the seasonal
                                                       mean for salinity at various depths, and surface
                                                       nutrients.  At the top, we have also shown the flow of
                                                       the Fraser River, as measured at Hope. The summer
                                                       influx of fresh water from the Fraser, with smaller
                                                       contributions from other rivers, is responsible for the
                                                       low summer salinities in the Strait.

                                                       However, although there is slight tendency for  above-
                                                       average flows to result in lower-than-usual surface
                                                       salinities, the other year-to-year variations shown are
                                                       still a mystery.




                Anomalies around the seasonal mean for salinity
                at various depths, and surface nutrients.
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