Collecting Water Quality Samples
Water is collected from numerous points at each study site. Back at the laboratory, this water will be analyzed to measure water hardness and alkalinity, nutrients (nitrogen, phosphorus), silica (needed by the diatoms that have silica glass cell walls), organic carbon, total suspended solids, turbidity, chlorophyll, and water color.
In very shallow water we take dip (grab) samples from just below the surface. Where water depths range from 1-3 meters (about 3-10 feet) we use a long tube (shown below) to collect an integrated water sample from the surface of the water down to 2 meters (6.6 feet).
In deeper water, we use standard Van Dorn water samples (pictured at left) that allow us to collect discrete samples from depths of 5 and 10 meters (about 16 and 33 feet).
At all locations we use instruments with sensors to measure temperature, dissolved oxygen, pH and EC25 (specific electrical conductivity, which estimates the total amount of salts in the water) from the surface to the bottom.
Documentation is crucial: The location of each water collection point, the field instrument data, transparency data, current weather and other important information are recorded on waterproof datasheets in the field.