Taking water sample

He is taking a water sample.  The tube is lowered into the lake, and water fills the tube.  The end of the tube that is held in the hand is blocked, so that the water will remain in the tube when the tube is pulled up.

Water can be tested for all sorts of chemical parameters and some biological ones.

Usually water is tested for (in order of frequency in Maine)
Phosphorus
Chlorophyll_a
Color
Alkalinity
Conductivity
Nitrogen compounds

This sample can also be used to check for dominant algal species

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