Testing for Quality

In May, LAON volunteers and two high school interns began water sampling in Norway’s lakes. Our focus is to monitor the levels of algae growth and the harmful chemicals that promote it. We will do sampling once a month at each lake until September.

We are collecting information on water clarity, color, phosphorus concentration, dissolved oxygen, temperature, algal concentrations, pH, alkalinity and conductivity.  All data will be added to the Maine State Department of Environmental Protection database.  All measurements are related directly or indirectly to how healthy a lake is and, if there are any signs of trouble, may point to a remedy. (If you’re interested in doing water sampling, we encourage you to contact us.)

One of the simplest tests for clarity involves lowering an eight inch black and white disk into the water until it disappears to measure what is known as the Secchi Depth. The measurement of total phosphorus content is of particular concern because that chemical leads to plant and algal growth. Using a sample tube, we scoop out half a cup of water, pack it in ice, and  send it to the Health and Environmental Testing Laboratory (HETL) in Augusta. To measure dissolved oxygen and temperature, we lower a probe to take measurements at one meter intervals from the surface to the bottom. Microscopic algae, also called phytoplankton, are often measured by determining the amount of chlorophyll, the chemical necessary for photosynthesis. We filter a sample of water through a glass fiber filter. The filter is then put in acetone at the HETL and analyzed in a spectrophotometer.

These measurements are all connected to lake water quality. The concentration of microscopic algae affects water clarity. The amount of algae is related, in part, to how much water runoff from products containing phosphates enter the lakes. During the summer months, many lakes form a warm surface layer and a cooler bottom layer. When organisms like algae die, bacteria break them down using up oxygen in the process. Much of this decay happens in the deeper layer, leading to low oxygen levels that could cause problems for fish and other organisms, and, possibly, bad smells like rotten eggs.

The data collected last season indicate that the lakes were in relatively good health. Total phosphorus and water clarity were in the excellent range, either improved or close to historic averages. Because the chlorophyll numbers were only in the good range, however, we need to keep a close eye on them to prevent problems with algal blooms. (The full 2014 report, prepared by Scott Williams of Lake & Watershed Resource Management Associates, is on our website.)

Look for us on your lake this summer – we’re working to keep it healthy!

By Stephan Zeeman