Calder Reservoir Algal Bloom Monitoring 2019

Update November 14, 2019

The Tri-County Health Department has removed the Warning Advisory for Calder Reservoir.

The HABs monitoring season ended on October 31, 2019. The Utah Department of Health and local health departments have determined that the health risk from HABs from primary contact recreation drops with the onset of colder temperatures.

The close of the monitoring season and removal of advisories doesn’t mean HABs are no longer present. HABs can persist throughout the fall and winter and can pose a potential threat to humans and pets. It’s important to recognize the signs of a bloom and take appropriate precautions. Recreators are advised to stay out of the water and avoid any contact with water or scum if they suspect a harmful algal bloom. Hunters and fishers should clean waterfowl and fish well and discard all guts.”

Update October 30, 2019

Toxin test results received from the Utah Public Health Lab (UPHL) for samples collected by the Division of Water Quality (DWQ) at the boat ramp at Calder Reservoir on October 14, 2019, showed anatoxin-a and microcystin levels well below the recreation health-based threshold for a Warning Advisory. Cyanobacteria cell-count concentration results are pending from PhycoTech.

A Warning Advisory indicates a moderate relative probability of acute health risk, cell-count density of 20,000 – 10 million cells per milliliter (cells/ml), microcystin levels of 4-2,000 micrograms per liter (µg/L), or anatoxin-a levels above non-detect.

Calder Reservoir remains under a Warning Advisory.

Data Summary

Boat Ramp

• Sample date: October 14, 2019
• Sample type: Elbow-depth integrated composite sample
• Microcystin: <2.0 micrograms per liter (µg/L)
• Anatoxin-a: <0.10 µg/L

Update October 15, 2019

Toxin test results received from the Utah Public Health Lab (UPHL) for samples collected by the Division of Water Quality (DWQ) at the Boat Ramp at Calder Reservoir on September 19, 2019, and October 2, 2019, showed anatoxin-a levels exceeding the recreation health-based threshold for a Warning Advisory. Microcystin levels were below the advisory threshold on both sample dates. Cyanobacteria cell-count concentrations are pending from PhycoTech.

The DWQ monitoring crew observed large amounts of cyanobacteria resembling green grass clippings, both in the water column and on the surface. Some of theses cyanobacteria had clumped together to form mats on the surface. There were some areas where the cyanobacteria were concentrated in shallow macrophytes (aquatic plants).

A Warning Advisory indicates a moderate relative probability of acute health risk, cell-count density of 20,000 – 10 million cells per milliliter (cells/ml), microcystin levels of 4-2,000 micrograms per liter (µg/L), or anatoxin-a levels above non-detect.

The Warning Advisory for Calder Reservoir remains in effect.

Data Summary

Access

• Sample date: October 2, 2019
• Sample type: Surface sample
• Microcystin: <2.0 micrograms per liter (µg/L)
• Anatoxin-a: 0.196 µg/L
• Cyanobacteria cell counts: Pending

Access

• Sample date: October 2, 2019
• Sample type: Elbow-depth integrated composite sample
• Microcystin: < 2.0 micrograms per liter (µg/L)
• Anatoxin-a: <0.10 µg/L
• Cyanobacteria cell counts: Pending

Boat Ramp

• Sample date: September 19, 2019
• Sample type: Surface sample
• Microcystin: 2.6 micrograms per liter (µg/L)
• Anatoxin-a: 0.197 µg/L
• Cyanobacteria cell counts: Pending

Boat Ramp

• Sample date: September 19, 2019
• Sample type: Elbow-depth integrated composite sample
• Microcystin: < 2.0 micrograms per liter (µg/L)
• Anatoxin-a: 0.133 µg/L
• Cyanobacteria cell counts: Pending

Update September 16, 2019

Toxin test results received from the Utah Public Health Lab (UPHL) for samples collected by the Division of Water Quality (DWQ) at the Boat Ramp at Calder Reservoir on September 5, 2019, showed anatoxin-a levels exceeding the recreation health-based threshold for a Warning Advisory in the surface sample. Microcystin levels were well below the advisory threshold in both samples.

The DWQ monitoring crew observed visible cyanobacteria that resembled grass clippings in the water column. The water had a green/brown hue. In some places, the cyanobacteria had clumped together. There was also evidence of dried cyanobacteria along the shore.

A Warning Advisory indicates a moderate relative probability of acute health risk, cell-count density of 20,000 – 10 million cells per milliliter (cells/ml), microcystin levels of 4-2,000 micrograms per liter (µg/L), or anatoxin-a levels above non-detect.

The Warning Advisory for Calder Reservoir remains in effect.

Data Summary

Surface sample

• Sample date: September 5, 2019
• Microcystin: <2.0 micrograms per liter (µg/L)
• Anatoxin-a: 0.14 µg/L

Elbow-depth integrated composite sample

• Sample date: September 5, 2019
• Microcystin: < 2.0 micrograms per liter (µg/L)
• Anatoxin-a: <0.10 µg/L

Update September 5, 2019

Cyanobacteria cell-count results received by the Division of Water Quality (DWQ) on September 4, 2019, for samples collected at the Calder Reservoir Boat Ramp on August 23, 2019, exceeded the recreation health-based threshold for a Warning Advisory. Cyanobacteria cell-count concentrations in the surface sample were at the higher end of the advisory threshold at approximately 1.1 million cells per milliliter (mL). The primary taxon in the samples was Aphanizomenon.

Toxin test results for anatoxin-a and microcystin were both non-detect. DWQ is now running new dilution curves for its enzyme-linked immunosorbent assay (ELISA) analysis for cyanotoxins. These different dilution ratios (1:1000 and 1:20) have changed the detection limit for microcystin from <0.10 micrograms per liter (µg/L) to <2.0 µg/L. The 1:20 dilution will detect toxin levels between 2 and 100 µg/L, and the 1:1000 dilution will detect toxin levels between 100 and 5,000 µg/L. These new dilution ratios should result in faster lab results. If further precision is needed, the lab will run additional dilutions.

The DWQ monitoring crew observed a visible bloom of cyanobacteria that resembled grass clippings during their August 23, 2019, visit to the reservoir. Some of these cyanobacteria had formed clumps on the surface of the lake near the shore. There was also evidence of past bloom material along the shore.

A Warning Advisory indicates a moderate relative probability of acute health risk, cell-count density of 20,000 – 10 million cells per milliliter (cells/ml), microcystin levels of 4-2,000 micrograms per liter (µg/L), or anatoxin-a levels above non-detect.

Calder Reservoir remains under a Warning Advisory.

Data Summary

Surface sample

• Sample date: August 23, 2019
• Microcystin: <2.0 micrograms per liter (µg/L)
• Anatoxin-a: <0.10 µg/L
• Cyanobacteria cell counts: 1,134,518 cells per milliliter (cells/mL)

Elbow-depth integrated composite sample

• Sample date: August 23, 2019
• Microcystin: < 2.0 micrograms per liter (µg/L)
• Anatoxin-a: <0.10 µg/L
• Cyanobacteria cell counts: 918 cells per milliliter (cells/mL)

Update August 13, 2019

Toxin test results from samples collected at Calder Reservoir on August 6, 2019, were detect for anatoxin-a. Detection of anatoxin-a exceeds the recreation health-based threshold for a Warning Advisory. Microcystin levels were well below the advisory threshold. Cyanobacteria cell-count results from PhycoTech are pending.

A Warning Advisory indicates a moderate relative probability of acute health risk, cell-count density of 20,000 – 10 million cells per milliliter (cells/ml), microcystin levels of 4-2,000 micrograms per liter (µg/L), or anatoxin-a levels above non-detect.

Calder Reservoir remains under a Warning Advisory.

Data Summary

• Sample Date: August 6, 2019
• Sample type: Elbow-depth integrated composite sample
• Microcystin: 0.264 micrograms per liter (µg/L)
• Anatoxin-a: 0.124 µg/L

Update August 5, 2019

Cyanobacteria cell-counts from samples collected on July 30, 2019, at Calder Reservoir were at the upper end of the recreation health-based threshold for a Warning Advisory. Toxin-test results for microcystin and anatoxin-a were both well below the health advisory threshold.

The Division of Water Quality (DWQ) monitoring crew observed visible cyanobacteria resembling small circular nodules and grass clippings. Cyanobacteria were evident on the surface and throughout the water column. The primary cyanobacteria taxon found in the samples was Aphanizomenon.

A Warning Advisory indicates a moderate relative probability of acute health risk, cell-count density of 20,000 – 10 million cells per milliliter (cells/ml), microcystin levels of 4-2,000 micrograms per liter (µg/L), or anatoxin-a levels above non-detect.

Calder Reservoir remains under a Warning Advisory.

Surface sample

• Sample Date: July 30, 2019
• Microcystin: <0.10 micrograms per liter (µg/L)
• Anatoxin-a: <0.10 µg/L
• Cell Counts: 2,857,308 cells per milliliter (cells/mL)

Elbow-depth integrated composite sample

• Sample Date: July 30, 2019
• Microcystin: <0.10 micrograms per liter (µg/L)
• Anatoxin-a: <0.10 µg/L
• Cell Counts: 1,169,730 cells per milliliter (cells/mL)

Update July 22, 2019

Follow-up water samples collected by the Division of Water Quality (DWQ) on July 11, 2019, were below cyanobacteria cell-count and toxin recreation health-based thresholds.

Matt Warner Reservoir, a waterbody approximately five miles northwest, is connected to Calder Reservoir via Pot Creek and also under a harmful algal bloom advisory. Because water from Matt Warner can flow into Calder Reservoir, the Tri-County Health Department has chosen to maintain the Warning Advisory for Calder Reservoir.

While cell-counts remain below health-based advisory thresholds, the predominant species continues to be Aphanizomenon, a cyanobacteria taxon that can produce both microcystin and anatoxin-a.

• Calder Reservoir Boat Ramp (elbow-depth integrated composite sample): <0.10 micrograms per liter (µg/L) of anatoxin-a; <0.10 µg/L of microcystin; cyanobacteria cell-count concentrations of 4,002 cells per milliliter (cells/mL)

Update July 11, 2019

Calder Reservoir Boat Ramp (elbow-depth integrated composite sample): <0.10 µg/L of anatoxin-a; <0.10 µg/L of microcystin; cyanobacteria cell-count concentrations of 4,002 cells/mL

Update July 3, 2019

Division of Water Quality (DWQ) scientists conducted follow-up sampling at Calder Reservoir on July 2, 2019. Cyanobacteria were still present but less abundant (visually) than the previous visit. Green clumps remained dispersed in the water column.

Scientists collected elbow-depth integrated composite samples at the boat ramp. Toxin test results from the Utah Public Health Lab (UPHL) on July 3, 2019, showed the samples were below the recreation health-based thresholds for an advisory.

• Calder Reservoir Boat Ramp (elbow-depth integrated composite sample): <0.10 µg/L of anatoxin-a; <0.10 µg/L of microcystin

While the sample results were below advisory thresholds, the presence of a visible bloom can serve as cause for the issuance of an advisory, since toxin levels can vary from day to day.

Calder Reservoir remains under a Warning Advisory.

Update June 21, 2019

The Division of Water Quality (DWQ) collected an elbow-depth integrated water sample at the Zelph Calder Reservoir Boat Ramp on June 11, 2019. The monitoring crew observed Isolated clumps of green cyanobacteria on the surface of the reservoir and throughout the water column.

DWQ received cyanobacterial cell-count concentration results from PhycoTech on June 20, 2019, of 103,720 cells per milliliter (cells/mL) at the boat ramp. These cell-count densities exceed the recreation health-based threshold for a Warning Advisory. Based on these data, the Tri-County Health Department has issued a Warning Advisory for the Zelph Calder Reservoir.

The Tri-County Health Department will be posting signs at the reservoir. Health officials will collect water samples next week.

Toxin screening tests were inconclusive and samples were delivered to the Utah Public Health Lab (UPHL) for further analysis. UPHL testing showed anatoxin-a and microcystin levels of <0.10 micrograms per liter (µg/L), which are well below the recreation health-based threshold for a Warning Advisory.

A Warning Advisory indicates a moderate relative probability of acute health risk, cell-count density of 20,000 – 10 million cells per milliliter (cells/mL), microcystin levels of 4-2,000 micrograms per liter (µg/L), or anatoxin-a levels above non-detect.