Volunteer Lake Monitoring Program

A Day in the Life of the Volunteer Lake Monitor

Volunteer lake monitors are often the first people to get their boats in the water in the spring. Starting in May or early June, they start their weekly visits to the deepest part of the lake to perform water quality monitoring activities. After anchoring the boat, the monitor begins by measuring water clarity with a Secchi disc. The Secchi disc method was originally developed by Italian scientist, Pietro Angelo Secchi, in 1865 and, due to its simplicity and reliability, remains one of the most widely used water quality monitoring instruments today. It is a weighted disc, eight inches in diameter, which is painted black and white in alternating quarters (see photo). The monitor slowly lowers the Secchi disc over the shaded side of the boat and notes the depth where it disappears. The disc is lowered an additional two feet and then slowly raised until coming back into view. After noting the depth of reappearance, the average of the two depths is calculated and recorded. The deeper the Secchi disc depth, the clearer the water and generally the better the water quality.

Every other week, the monitor collects a water sample that is used to measure chlorophyll-a concentrations. Chlorophyll-a is a pigment found in all green plants, including algae. Measuring the amount of chlorophyll-a in a water sample provides a fairly accurate estimate of the amount of algae in the water. Collecting this water sample is one of the monitor's most difficult tasks. After determining the Secchi disc depth, the monitor collects the water sample in the same location. An 'integrated sampling device', which is a weighted container with a small hole on the top for water entry (see photo), is lowered down through the water column to twice the Secchi disc depth. Research has determined that sunlight penetration, and therefore plant growth, is limited to approximately two times the Secchi depth. The water sample has to be representative of the entire water column, so the volunteer has to lower and raise the water sampling device at such a rate that twice the Secchi disc depth is reached and so that the container is not overflowing upon reaching the surface. Although more difficult than measuring Secchi depth, with practice our volunteers have consistently and quickly mastered this water sample collection method.

Once the water sample has been collected, the volunteer monitor forces a specific volume of water through a filter paper inside a syringe filtering device. The filter paper is carefully placed into a test tube, wrapped in tinfoil to prevent exposure to sunlight and stored in the freezer. At the end of the sampling season, the accumulated test tubes with filters of all the lake volunteer monitors are delivered to the University of Michigan Bio-station for analysis. A low level of chlorophyll-a indicates relatively low algae abundance and good to excellent water quality, while a high level of chlorophyll-a indicates dense algae growth and generally poor water quality.

Starting in 2002, volunteers were equipped with thermometers and began measuring surface water temperature. Additional parameters under consideration for monitoring include phosphorus and microsystin. Phosphorus would provide valuable information about nutrient levels in our lakes and would also help further define the trophic status of our lakes. Microsystin is a toxin produced by some strains of the Blue-green algae, Microsystis. It has been speculated that Microsystis blooms are becoming more common due to the far-reaching effects of zebra mussel proliferation in Michigan lakes. As this toxin is potentially harmful to animals (including humans) it may be prudent to include it in our monitoring programs. However, monitoring phosphorus and microsystin will depend upon many factors, chief among which are funding and volunteer interest.

Contact Us|Search