I have been helping to process samples brought up when the CTD is deployed. The CTD measures conductivity, temperature, and depth (via pressure). Niskin bottles, attached to the rosette, can be closed at different depths to collect water from a given depth. As the CTD is going down through the water, parameters such as temperature, salinity, and chlorophyll level are measured. That is marked on a log. Later, when water is collected in the niskin bottles, a sample of water is taken from the niskin bottle that corresponds to the appropriate depth for what is being analyzed; in this case, chlorophyll, but other teams analyze other parameters.
After removing samples of water from the correct bottle (remembering to rinse and repeat times 3), the water is filtered using a vacuum filtration apparatus. The filters appear to be very faintly greenish against the white background. Each of the filters is placed in a labeled container and then stored in a cold room for analysis upon return to the lab. The samples I filtered will be analyzed for POM (particulate organic matter).
Although filling bottles and running a vacuum filtration device are not overly exciting tasks by themselves, I am enjoying it because it reinforces the concepts I teach during classroom labs - pay attention to details, don't cross contaminate, keep an orderly work station, record data in an organized manner.
CTD with niskin bottles.
Vacuum filtration process.
Question and Answer
Question: Here is an image of what is shown as the CTD is being lowered through the water column. At the required depth, a signal is sent and the designated bottle closes. Green represents chlorophyll. At about what depth do you find the maximum chlorophyll level in the chart shown below?
Raw data from a CTD deployment.
Answer From Last Q: The outer walls (frustules) of diatoms are made of silica.
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