The key takeaways from the 2021 monitoring season are:
• This year, Green Lake had less-clear water, with high nutrient concentrations and moderate 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 2021 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 still noticeably higher than values observed before the alum treatment that occurred in spring 2016. • An algal bloom was sampled for toxin testing in October. Toxin testing found elevated microcystin concentrations: 16.1 µg/L, above the Washington State Recreational Guideline of 8 µg/L. There was a Toxic Algae Warning on the lake for a couple weeks in October.
Please see below for a link t
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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).
