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INTRODUCTION
In this chapter, data products related to phytoplankton productivity, water clarity, and reflection from sediments and the sea floor are analyzed. The months of April 2002 and April 2003 had very different water flow conditions in the Chesapeake Bay watershed, due to very low precipitation in April 2002 compared to very heavy precipitation in April 2003. These differenct conditions caused very apparent changes in the biological properties in the waters of the Bay and along the coast.
Data Sets for this Chapter
- SeaWiFS Chlorophyll
- SeaWiFS K490
- SeaWiFS nLw(555)
- MODIS Chlorophyll
- MODIS Water-Leaving Radiance
Visualizations for this Chapter
- Area Plot (Giovanni)
- Histogram (NEO)
Location Map and Coordinates
 
Step-by-Step
Refer to the pages for Giovanni functions and NEO functions if you are unfamiliar with the functions described below.
Area Plot: Giovanni
- Select the area.
- Parameter: Chlorophyll a concentration
- Plot Type: Lat-Lon Map, Time-Averaged
- Time Period: Begin Year - 2002; Begin Month - April; End Year - 2002; End Month - April.
- Customized Color Scale: Minimum - 0.5; Maximum - 10.0
- Generate Plot
Click the image to see it full-size. (You can do this for any of the images in the Step-by -Step section.)
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Area Select (NEO)
- Select MODIS Chlorophyll and MODIS Water Leaving Radiance for the month of April 2003.
- Select the area with the coordinates shown above. (To get the right area, it is easier to enter the coordinates than to click-and-drag, because this is a small region.)
- Launch the analysis. The two images will look like this. Even though only a pre-defined color scale is available, the Histogram function will display the range of values.
- Select an area similar to the one shown below. This is an area in the lower central Chesapeake Bay.
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Area Plot: Giovanni
- Change the Time Period: Begin Year and End Year to 2003.
- Generate Plot.
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Histogram (NEO)
- Using the selected area, click the Histogram button.
The histogram will appear similar to this:
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Area Plot: Giovanni
Perform the same steps as above, with the following parameter:
Use the Pre-Defined Color Scale.
The results should look like the images below (April 2002 at top, April 2003 at bottom).
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Area Plot: Giovanni
Perform the same steps as previously for the Giovanni area plots, with the following parameter:
- Normalized water-leaving radiance at 555 nm
Use the Pre-Defined Color Scale. The results should look like the images below (April 2002 at top, April 2003 at bottom).
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Extended Investigations
This chapter shows relationships between phytoplankton productivity and optical properties of the Chesapeake Bay during a very dry month (April 2002) compared to a very wet month (April 2003). During the wet month, more nutrients were available that could be utilized by the phytoplankton for growth. Higher concentrations of phytoplankton influenced the water clarity, which is indicated by the higher values in April 2003 of K490, the diffuse attenuation coefficient at 490 nanometers. The normalized water-leaving radiance at 555 nm (nLw555) is primarily sensitive to reflection from sediments or from the sea floor, if the sea floor is shallow. Think about why nLw555 is higher in April 2002 compared to April 2003.
The Chesapeake Bay is affected by nutrients from "point sources" and "non-point sources". Determine the difference between these types of sources and consider ways to control the nutrients delivered into the Bay from each. Consider why excess nutrients affect the water quality of the Bay.
The once-thriving and famous oyster population of the Chesapeake Bay is nearly gone, due primarily to disease. Oysters, as well as the fish called menhaden, are filter-feeders; they filter the water through special structures to extract and consume the phytoplankton. Consider how the loss of millions of oysters from the Chesapeake Bay has affected its water quality.
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Atmos Composition
