LEA visits Long Lake’s middle basin twice a month in May through September. This year, the average total phosphorus concentration and the average chlorophyll concentration were near their long-term averages, while the average clarity reading was more shallow than the long-term average. The average deep-water phosphorus value was less than 10 ppb above surface water phosphorus values, which suggests phosphorus recycling was not problematic. Long-term trend analysis indicates chlorophyll-a concentrations are decreasing while clarity readings and total phosphorus concentrations are stable. This year’s average surface water temperature was similar to last year’s average surface water temperature. Oxygen depletion was observed at the deepest parts of the lake beginning in early August. Gloeotrichia echenulata colonies were observed beginning in early July this year with densities ranging from 1 – 3 on the Gloeo density scale.
Long Lake middle basin’s surface water chlorophyll (ppb), phosphorus (ppb), and Secchi depth (meters) data comparison. Colored areas represent the long-term range of values, from minimum to maximum. Area thickness indicates frequency of measurements at that value. Area thickness increases as more measurements are reported at that value. The vertical black line represents the long-term average value. The large red dot represents 2024’s average value. The small red dots represent individual readings taken in 2024.
Gloeotrichia echinulata (a type of cyanobacteria (blue-green algae) commonly found in low-nutrient waters) can be seen with the naked eye. Gloeo density is reported as a value ranging from 0 – 6, based on the number of Gloeo colonies seen through a Secchi scope. Higher values indicate more Gloeo colonies. The middle basin’s Gloeotrichia echenulata colonies were observed beginning in early July this year with densities ranging from 1 – 3 on the Gloeo density scale.
