What exactly are we counting?
The following pictures are petri dishes ("plates") on which we've grown bacteria from water samples. Each yellow dot is about as big as the head of a pin. We count these dots to get an idea of how many bacteria were in our water sample.

This is a photo of the B1 sample from Dec. 4, 2001. It shows four CFU (colony forming units) of fecal coliform bacteria. The size of sample was 100mL of water.
The result is reported as 4 CFU/100mL, which is a very low level.
These numbers are reported in our charts and tables.

This photo is of B3 from Dec. 4, 2001.
It shows 13 yellow dots and one purple dot. We only count the yellow.

The D1 sample from Dec. 4, 2001 show a much higher level of bacterial contamination.
The count was recorded as 203 CFU/100mL. Bacterial levels this high in the streams that flow into the Webhannet Estuary contribute to the closure of clam flats in Wells, Maine.