Monitoring chlorophyll in situ to
derive primary production in a coastal estuary
Washington State Dept. of Ecology deployed moored WETStars and CT meters at four locations in Willapa Bay WA from 1998 through 2000. The goals of this study were to evaluate watershed vs. oceanic influence on the estuary and to assess controls on primary production.
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 Coast Guard naviational piling used to moor sensor cage |
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| WETStar being deployed in Willapa Bay WA. Floats kept
the sensor cage at a constant depth of 1 meter, rising and falling
with tides that change by as much as 4 meters.
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| Chlorophyll fluorescence was
measured at a 15-minute resolution for over three years in the turbid,
productive and physically dynamic estuary, severely testing the performance
of the sensors.
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Click on the thumbnail below for larger image |
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Data from the WETStar shows distinct and episodic blooms and substantial interannual variation. In 1998, the ocean thermocline was depressed and upwelling brought less nitrate to the surface. In 1999, the the thermocline was shallow and surface nitrate was more plentiful. Because blooms are episodic, the ability to measure chlorophyll on fine time-scales is essential to make these comparisons. The DOE also derived a multiple linear regression equation to estimate primary production from chlorophyll, PAR, and an upwelling index (right, above). This equation permits "now-casting" of phytoplankton from remote and in situ measurements. |
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