2021 Cynobacteria Testing in Lake Garfield

Every two weeks starting in June, Shannon Poulin has been taking water samples from our lake. See her reports below.

June 9, 2021

On June 9, 2021, two samples were taken one at the surface in the big bowl and the other at 10 feet in the big bowl. The phycocyanin levels were at 0.10 parts per billion for both samples which is extremely low. The cell counts were 600 cells/mL of Microcystis and 40 cells/mL of Dolichospermum at the surface for a total of 640 cells/mL. The cell counts at 10 feet was 430 cells/mL of Microcystis and 30 cells/mL of Dolichospermum for a total of 460 cells/mL. The cell counts are nowhere near the state’s threshold of 70,000 cells/mL. At this time the lake is okay.

Compared to last year the results are the same as last year and that the cyanobacteria levels are low. However, at this time last year these two genera were not present and Aphanizomenon and Woronichinia were present. Also, to note is that the surface temperature of the lake at sampling time this year was 5 degrees Celsius warmer than at the same time last year.

The temperature and dissolved oxygen (mg/l) were collected 1 to 25 feet. The oxygen increased from 10 to 15 feet deep then decreased by half at 20 feet. Then dropped below 1 mg/l at 25 feet. I took a sample at 10 feet because the dissolved oxygen levels are increased and is a good indication that cyanobacteria are in the area as they can photosynthesize. The secchi depth was 11.3 feet meaning the water was pretty clear.

Figure 1. Estimated Lake Stratification

June 21, 2021

On June 21, 2021, one sample was taken at Michael’s dock and one at 10 feet in the Big Bowl. The phycocyanin levels were at 0.10 parts per billion which is extremely low for both samples. The cell counts at Michael’s dock were 960 cells/mL of Microcystis. The cell counts at 10 feet were 760 cells/mL of Microcystis. Neither location had cell counts that are near the states threshold, therefore the lake is safe at this time.

Compared to previous years, Microcystis was the only cyanobacteria found this year whereas Dolichospermum and Aphanizomenon were also found. The total cell counts were also higher than this time last year.

The temperature and dissolved oxygen were taken at 1 to 20 feet. The oxygen levels were steady then slightly increased going towards the bottom. The secchi disc had a reading of 11.9 feet. Of note, it was very breezy at the time of sampling and even with an anchor, the boat drifted.

Figure 1. Estimated Lake Stratification

July 5, 2021

On July 5, 2021, one sample was taken at the surface of the Big Bowl and one at 15 feet in the Big Bowl. The phycocyanin levels were at 0.10 parts per billion which is extremely low for both samples. The cell counts at Michael’s dock were 200 cells/mL of Microcystis and 1,200 cells/mL of Woronichinia for a total of 1,400 cells/mL. The cell counts at 10 feet were 375 cells/mL of Microcystis. Neither location had cell counts that are near the state’s threshold of 70,000 cells/mL, therefore the lake is safe at this time.

Compared to the last sampling, the cell counts for Microcystis have decreased. Also of note is that Woronichinia has not been seen at this time of year in the previous years.

The temperature and dissolved oxygen were taken at 1 to 25 feet. The oxygen levels were steady until 20 feet then drops below 2 mg/L at 25 feet. The bottom of the lake has lost its oxygen since the last sampling. The secchi disc had a reading of 7.9 feet which has decreased the clarity of the water by a couple of feet since the last sampling.

July 19, 2021

On July 19, 2021, one sample was taken at the surface of the Big Bowl and one at 15 feet in the Big Bowl. The phycocyanin levels were at 0.10 parts per billion which is extremely low at the surface while at 15 feet the phycocyanin levels were 21.62 parts per billion. The cell counts at Michael’s dock were 1,600 cells/mL of Microcystis and 600 cells/mL of Limnoraphis for a total of 2,200 cells/mL. The cell counts at 15 feet were 1,600 cells/mL of Microcystis, 9,200 of Limnoraphis, and 800 cells/mL of Aphanizomenon for a total of 11,600 cells/mL. Neither location had cell counts that are near the state’s threshold of 70,000 cells/mL, therefore the lake is safe at this time.

Compared to the last sampling, the cell counts have increased significantly and also the genus’s Limnoraphis and Aphanizomenon are present. Also of note is that Aphanizomenon has not been seen at this time of year in previous years.

The temperature and dissolved oxygen were taken at 1 to 25 feet. The oxygen levels were steady until 20 feet then drops below 2 mg/L at 25 feet. The bottom of the lake’s oxygen has not changed since the last sampling. The secchi disc had a reading of 8.6 feet which has increased the clarity of the water by a foot since the last sampling.

Figure 1. Estimated Lake Stratification

August 2, 2021

On August 2, 2021, one sample was taken at the surface of the Big Bowl and one at 17 feet in the Big Bowl. The phycocyanin levels for both samples were 0.10 parts per billion which is extremely low. The cell counts at the surface were 1,400 cells/mL of Microcystis. The cell counts at 17 feet were 600 cells/mL of Microcystis. Neither location had cell counts that are near the state’s threshold of 70,000 cells/mL, therefore the lake is safe at this time.

Compared to the last sampling, the cell counts have decreased significantly. Compared to this time last year, the cyanobacteria counts are about the same. The oxygen levels are similar except that the lake at this time has less oxygen then it did last year.

The temperature and dissolved oxygen were taken at 1 to 25 feet. The oxygen levels were steady until 15 feet then drops close to 2 mg/L at 20 feet and below at 25 feet. The secchi disc had a reading of 8.5 feet which has not changed since the last sampling.

Figure 1. Lake Stratification

August 16, 2021

On August 16, 2021, one sample was taken at the surface of the Big Bowl and one at 17 feet in the Big Bowl. The phycocyanin levels for both samples were 0.10 parts per billion which is extremely low. The cell counts at the surface were 1,200 cells/mL of Microcystis. The cell counts at 17 feet were 240 cells/mL of Microcystis and 400 cells/mL of Limnoraphis for a total of 640 cells/mL. Neither location had cell counts that are near the state’s threshold of 70,000 cells/mL, therefore the lake is safe at this time.

Compared to the last sampling, the cell counts have stayed the same. Compared to this time last year, the cyanobacteria counts are about the same. The oxygen levels are similar except that the lake at this time has less oxygen then it did last year.

The temperature and dissolved oxygen were taken at 1 to 25 feet. The oxygen levels were steady until 10 feet then drops below 2 mg/L at 20 feet. The secchi disc had a reading of 8.8 feet which has not changed since the last sampling.

Figure 1. Lake Stratification where 0 is the lake surface

September 3, 2021

On September 3, 2021, one sample was taken at the surface of the Big Bowl and one at 20 feet in the Big Bowl. The phycocyanin level for the surface was 0.10 parts per billion which is extremely low. For the 20-foot depth sample, the phycocyanin levels were 28.31. The cell counts at the surface were 400 cells/mL of Microcystis, 1,600 cells/mL of Dolichospermum, and 1,200 cells/mL of Aphanizomenon for a total of 3,200 cells/mL Neither location had cell counts that are near the state’s threshold of 70,000 cells/mL, therefore the lake is safe at this time.

Compared to the last sampling, the cell counts have increased. Compared to this time last year, the cyanobacteria counts are about the same and Microcystis was observed at the surface at this time last year.

The temperature and dissolved oxygen were taken at 1 to 25 feet. The oxygen levels were steady until 15 feet then drops below 2 mg/l at 20 feet. The secchi disc had a reading of 7.5 feet which has decreased since the last sampling.

Figure 1. Lake Stratification where 0 is the lake surface.

September 13, 2021

On September 13, 2021, one sample was taken at the surface of the Big Bowl and one at 20 feet in the Big Bowl. The phycocyanin level for both locations was 0.10 parts per billion. The cell counts at the surface were 1,350 cells/mL of Microcystis. The cell counts at 20 feet were 850 cells/mL of Microcystis. Neither location had cell counts that are near the state’s threshold of 70,000 cells/mL, therefore the lake is safe at this time.

Compared to the last sampling, the cell counts have significantly decreased. Compared to this time last year, the cyanobacteria counts are about the same and Microcystis was observed at the surface at this time of year.

The temperature and dissolved oxygen were taken at 1 to 25 feet. The oxygen levels were steady until 15 feet then drops below 2 mg/L at 25 feet. The secchi disc had a reading of 8.5 feet which has increased since the last sampling.

Figure 1. Lake Stratification where 0 is the lake surface