The key takeaways from the 2020 monitoring season are:
• Green lake has to have fairly clear water, with high nutrient concentrations and high algal growth. • Nitrogen-to-phosphorus (N:P) ratios were below 25 throughout the monitoring season. This indicates the potential for algal blooms to be dominated by cyanobacteria (which have the ability to produce toxins). • Average 2020 chlorophyll, nitrogen, and phosphorus concentrations were noticeably higher than values observed in 2018. Although chlorophyll and nitrogen values are not as high as 2019 averages, these concentrations are all also noticeably higher than values observed before the alum treatment that occurred in spring 2016. • An algal bloom was sampled for toxin testing in September. Toxin testing found low concentrations of algal toxins, well below the Washington State Recreational Guidelines.
Please see below for a link to the full 2020 Green Lake Monitoring Report.
Click image to enlarge
The average of these three TSI indicators during the growing season can be used to place lakes in one of three broad categories: <40 = oligotrophic (low productivity), 40 to 50 = mesotrophic (moderate productivity) >50 = eutrophic (highly productive).