Jackson Lake Buoy Dashboard

Jackson Lake
Buoy Dashboard

Readings as of 9/11/2024 7:00 am
Unless otherwise indicated

Temperature: The water temperature reading is taken 1 meter, or about three feet, underwater. The changes in water temperature are much smaller compared to changes in air temperature because water has a high heat capacity. In other words, it takes more energy to warm the lake up in the spring (relative to the air) and the lake stays warmer into the fall even as air temperatures drop. You can see the hour-to-hour or day-to-day changes in water temperature are much less compared to air temperatures.

The air temperature reading is taken from the antenna attached to the buoy, just above the surface of the water. Air temperatures regularly change 10 to 30 degrees Fahrenheit in one day, but water temperature may only change by 1 to 2 degrees. The difference is because air has a much lower heat capacity than water. In other words, the energy from the sun can warm air by several degrees in several hours, whereas much more energy is needed over days or even weeks to warm water by the same amount.

Dissolved Oxygen: Dissolved oxygen in the water is critical for the survival of aquatic organisms. Oxygen is produced by algae and aquatic plants in the lake via photosynthesis and can exchange with the air via physical diffusion. While the surface water of lakes may have ample oxygen for fish and invertebrates, deeper waters can experience very low oxygen levels making this habitat difficult for many organisms to survive. On most days, dissolved oxygen increases during the day and decreases at night, which can be likened to the “pulse” of the entire biological community of the lake.

O₂ % Saturation: The amount of oxygen in the water can be expressed as a concentration (mg/L) or as a percent relative to saturation. When the water is 100% saturated, the oxygen in the water is in equilibrium with the oxygen in the air immediately above the lake. The lake can have more oxygen than the air (>100%) when algae are photosynthesizing and producing oxygen. Similarly, lakes can be undersaturated with oxygen (<100%) when fish, invertebrates, and bacteria are highly active, consuming oxygen in the water. Undersaturation is a more common state of lakes, especially at nighttime when photosynthesis is not occurring.

Chlorophyll: Chlorophyll-a is a pigment present in algae and plants that is responsible for photosynthesis. The measurement estimates the concentration of algae present in the water column. The small algae floating in the water, known as phytoplankton, are critical for the food web of the lake, providing the energy for zooplankton, invertebrates, and fish. However, too much algae can cause unsightly blooms, which may cause health concerns to humans and the lake ecosystem if they occur frequently and persist over time.

Dissolved Organic Matter: Dissolved organic matter (DOM) is an estimate for the amount of dissolved carbon present in the lake. The carbon comes from decaying plant matter in the lake or is washed into the lake from the surrounding watershed. In northern Wisconsin and elsewhere, DOM gives many lakes their distinctive brown color. The brown coloration limits how deep sunlight can reach into the water, so lakes with more DOM often have less algae. In general, the DOM concentration of a lake does not change much, but may show gradual increases or decreases across seasons and following rain events or extended dry periods.

Specific Conductivity: Specific conductivity measures the ability of water to pass an electric current, which is affected by ions dissolved in the water. In general, conductivity is stable for most lakes, but gradual or stepped increases over time can indicate inputs of pollution. The typical range of conductivity in freshwater ecosystems is between 10 and 200 μS/cm, but much higher in saltwater, ranging from 1,000 to 10,000 μS/cm.

Northland College