Volunteers monitored Pine Lake from the 1980s through 2014. This lake in Sammamish is clear, lightly buffered against pH change, and currently low in primary productivity (oligotrophic) with very good water quality. Productivity has remained steady since 1998, and nutrients show no strong trends. Diversion of a small inlet occurred in 1988 to address high nutrient inputs. The lake has a Lake Management Plan completed by the city.
Thermal stratification is stable in summer, but sediments release very little phosphorus to deep water, while minor ammonia increases indicate oxygen remains present. Nitrogen to phosphorus ratios in the upper water are above 25:1 during the summer, which does not favor cyanobacteria. Few reports of toxicity have occurred, and levels have been low.
Red swamp crayfish have invaded the lake and there is a project underway to control them through trapping. Pine Lake has a car top boat launch at the public park.
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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).