Blue-Green Algae and Water Quality Data Analysis Report

Shubenacadie Watershed Protection Society

Blue-Green Algae and Water Quality Data Analysis Report

Megan Elliott 

August 26, 2022

Edited SWEPS May’23

Introduction to SWEPS BGA Monitoring 

The goal of the SWEPS Blue Green Algae (BGA) project is to identify the sources of the pollutants that contribute to the growth of cyanobacteria blooms. The object of our testing program is to identify high risk areas in the watershed and hopefully be able to predict when the blooms are imminent. 

The project was implemented in the late spring of 2021, and so, includes data from the past two field seasons, 2021 and 2022.  SWEPS water quality monitoring program consists of 27 water sampling locations and are broken out into two broad categories, standard and enhanced (fig 1, table 1).  The enhanced blue-green algae (BGA) test sites, 14 locations, have additional chemical analyses, specifically phosphorus and nitrogen tests. Ideally, these sites are tested at least 3 times in each field season and include small brooks, lake shores, etc. and can have a wide range of values, so it is important to note the site conditions when analyzing. Water quality parameters can have a wide range of values so it is important to note weather conditions at the time of sampling and note the quality of riparian zones, urban development, and chemical runoff. 

BGA parameters, also measured by HRM, Municipality of East Hants, Halifax Water, Dalhousie University, and SWEPS historical data can show where high nutrient locations, how these are changing, and potential causes for changes. The main questions SWEPS wanted to know were: Are there any areas of concern that show up in the parameters on the map? And do any of these site parameters change over time, indicating problem areas? 

Summary of BGA testing locations for 2021 and 2022:

There were a total of 114 water samples taken at these BGA test site locations in the 2021 and 2022 field seasons with 40 samples taken in 2021 and 74 samples in 2022.  There were 69 standard samples taken in the 2021 and 2022 field season with 39 samples taken in 2021 and 30 in samples in 2022.  The final water sample total is 183.  

Figure 1. SWEPS testing location

AreaSite IDDescriptionCategorySample CountLatitudeLongitude
A LakeALKSt. Andrews ParkEnhanced844.8231-63.6289
Annand BrookANNBRInlet to Little Grand LakeEnhanced844.95374-63.5908
Black’s BrookBLACKBRA Lake outlet – Near Lockview HSStandard644.82221-63.6192
First LakeFRSTLKINFirst Lake – Inlet by bridgeStandard944.77642-63.6738
Fish LakeFSHLKOUTAFish Lake OutletEnhanced1044.90537-63.5856
Fish LakeFSHLKOUTBStream btw Fish Lk and Grand LkEnhanced444.90565-63.5878
Fletcher LakeFLTCHBHDock (4175 NS Trunk 2)Enhanced644.85275-63.6114
Grand LakeGRNDLKLPBLaurie Park beachStandard544.88504-63.6006
Grand LakeGRNDLKOPBLOakfield Park Boat LaunchEnhanced844.91969-63.5787
Grand LakeGRNDLKSULLYSSully’s Campground BeachEnhanced844.97228-63.5666
Kinsac LakeKNSCLKOUTRawdon River – Kinsac Lake outletStandard544.8625-63.6276
Lake ThomasTHMSLKCHEEMACHEEMA dockEnhanced644.78877-63.6052
Lake ThomasTHMSLKLTGSGordon Snow Comm Cntr dockEnhanced844.81447-63.6138
Lake WilliamLKWLMIN2Marshall Brook – Inlet to LK WilliamStandard544.75274-63.577
Lake WilliamLKWLMIN7Skerry Brook – Inlet to LK WilliamStandard744.77725-63.5875
Lake WilliamLKWLMOUTWaverley Park DockStandard1544.78549-63.5989
Laurie BrookLAURBRLaurie Prov. Park – Inlet to Grand LKEnhanced344.88283-63.5983
Lock 4LOCK4Lock 4Enhanced144.82781-63.6132
Miller Lake MLRLKOUTOutlet – Inn on the Lake parking lotEnhanced844.80794-63.6081
Perry LakePRYLKINTrail off the small walking bridgeEnhanced644.79751-63.6238
Powder Mill LakePDMLLKOUTPowder Mill Lake – Outlet by parkStandard744.77228-63.6067
Second LakeSCNDLKOUTSecond Lake outlet – off train tracksStandard544.78499-63.6377
Shubenacadie CanalFAIRFairbanks centre off dockEnhanced344.7022-63.5546
Shubenacadie CanalSHUBIEShubie Trail Head – near trail bridgeStandard444.73939-63.5569
Shubenacadie RiverLOCK6Lock 6Enhanced944.94099-63.5595
Soldier LakeSLDRLKIN1Soldier Lake Inlet – Preeper BrookStandard1044.83076-63.5701
Soldier LakeSLDRLKOUTSoldier LK outlet-Top of Tillman BRStandard1644.82592-63.5848
Third LakeTHRDLKOUTOff Winley Dr Trail – Third LK OutletStandard844.78737-63.6292

Table 1. SWEPS testing locations

After discussing with Rob Jamieson’s lab and the AGAT lab, where the professional samples are taken, it was determined that for BGA testing, SWEPS needed to test for Total Phosphate and Total Kjeldahl Nitrogen (TKN). Dr. Tri Nguyen-Quang from Dalhousie also suggested both phosphorus and nitrogen. For the form of nitrogen, TKN, in particular, this form is needed due to the bioavailability of this form of nitrogen for aquatic life such as plants and algae. Although SWEPS data points for phosphorus and nitrogen are few, there is an AECOM report from 2012 with the average and standard deviation values for phosphorus. This report also had N:P ratios, but it appeared this was total nitrogen and not total Kjeldahl nitrogen, so these nitrogen values cannot be compared. The Municipality of East Hants provided a spreadsheet of their data from 2009 to 2019 with phosphorus, TKN, and other variables. This allowed some spatial and temporal analysis of these variables.

Known BGA Locations

Blue-green algae has been found in many of the lakes within the watershed, particularly in those areas where human activities are most prevalent.  

Figure 2. Some reported BGA locations from 2021

Temporal Distributions of SWEPS Data

SWEPS data collection is done mostly during the summer, shown in the Figure 3 distribution, with the summer co-op students, but some testing is done in the off season. There was a large spike in testing around the 70s and 90s, shown in Figure 4, which could affect spatial visualization, since there were only a couple of sites being tested and there may be changes over time.  You can see the few sites that had numerous tests in that time period in Figure 5, which could also affect the data visualization. Testing has been increasing in the past 10 years as well as the number and spatial distribution of sites, which is highly beneficial for analysis, but to the limit of the past 10 years. 

Figure 3. Distribution of SWEPS testing points over the months

Figure 4. Distribution of SWEPS data over the years

Figure 5. This shows the distribution of samples at different locations

When analyzing SWEPS data these temporal distributions of data points must be taken into consideration, because there are seasonal, spatial, and possibly yearly changes in some parameters. For instance, if one site has only been measured in the off season and other sites were only measured in the summer, this will have a great impact on spatial distribution variables and the trends over time. Seasonally changing parameters included dissolved oxygen, temperature, and salinity, shown below in Figures 6 to 8. No other SWEPS variables showed monthly trends. Additionally, TKE appears to drop in the fall and Phosphorus spikes in September. These changes could be because of changes in sunlight, ambient temperature, evaporation, and rain frequency and intensity.

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Figure 6. Dissolved Oxygen levels changing over the months

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Figure 7. Water temperature changing over the months

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Figure 8. Salinity levels changing over the months

Figure 9. TKE levels over the months, averaged from 2009 to 2019

Figure 10. Total Phosphorus levels over the months, averaged from 2009 to 2019

Some parameters without seasonal changes that have been rising over time are turbidity, conductivity, and pH in Figures 11 to 13. This could be due to climate change, urban development, increased chemical runoff, or ecosystem recovery. Cam (SWEPS volunteer from BIO) has suggested that pH is rising due to the lack of acid rain as that environmental issue is being solved (Monica Forestell). Statistics would need to be done to properly determine the significance of different factors on different parameters.

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Figure 11. Turbidity increasing since the 1980s

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Figure 12. Conductivity increasing since the 1980s

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Figure 13. pH increasing since the 1980s

The AECOM report data only shows the average and standard deviation from 2002-2011 of the lakes they tested. This data can be used in the spatial analysis but is not included in Figure 14. This figure shows phosphorus decreasing over time in the East Hants data from 5 locations in the Shubenacadie watershed. This may mean phosphorus levels are decreasing across the watershed, but this does not test specific areas of concern, apart from SWPP5, where BGA was encountered by SWEPS employees in July 2022. In Figure 15, TKN did not seem to have the same trend. This parameter rose and fell around 2012 with a couple of spikes around 2016. The SWEPS data from 2022 with the East Hants and AECOM data may show a trend when the SWEPS data is implemented. 

Figure 14. Temporal change of phosphorus at 5 locations in the watershed, from East Hants values

Figure 15. Temporal change of TKN at 5 locations in the watershed, from East Hants values

Spatial Distributions of SWEPS Data

The non-seasonally changing parameters are more easily interpreted on maps, so turbidity, pH, TDS, and specific conductivity, and phosphorus were mapped (Figures 16 to 19). Specific conductivity, turbidity, pH, and TDS, all are highest in Downtown Dartmouth and Bennery Brook. For specific conductivity and TDS, this is more toward the Shubenacadie River end of Bennery Brook. There are a few outliers in this data, including the specific conductivity and TDS as First Lake, which have elevated levels. Turbidity and pH also have elevated levels around Miller Lake. The data in these areas should be investigated to see if there is any change over time. It’s also important to note how many data points were taken at any outlier sites and when these points were taken. The readings from the airport culvert under the highway were very high, as seen in field observations and may not have been in the data, which should be investigated. First Lake’s very high readings for one data point in field observations was likely from the loads of cut grass and plant debris that has washed up on shore after a big rain. This  data point could possibly be taken out of the maps to avoid skewed results.

Figure 16. Distribution of SWEPS specific conductivity data

LocationLatLongConduct uS/cm AvgConduct uS/cm CountConduct uS/cm MinConduct uS/cm MaxConduct uS/cm St DevYear MinYear Max
A Lake44.823100-63.628875105.13778.5115.812.532320212022
Annand Brook44.953745-63.59074954.74826.494.020.833420182022
Bennery Brook44.927000-63.535660265.6510240.3510.6128.767320182022
Black’s Brook44.822208-63.619153107.63697.8112.55.306120212022
Charles Lake44.736123-63.555177255.117178.0294.836.845520182022
First Lake44.776367-63.673624553.167242.2707.0154.064120182022
Fish Lake44.905371-63.58556197.80793.0102.63.405420212022
Fletcher Lake44.841469-63.612036143.7314032.0256.044.762619902022
Grand Lake44.909608-63.602937107.841783.6129.88.670320212022
Holland Brook44.847397-63.60378382.572425.0164.145.446820132017
Kinsac Lake44.828792-63.65429297.60864.9203.545.457020182022
Lake Loon44.711137-63.515620260.102189.4330.899.984920182018
Lake Thomas44.801883-63.608091187.3115166.9213.712.966520212022
Lake William44.773180-63.590181146.064529.5254.161.951320182022
Laurie Brook44.882825-63.598258105.05285.0125.128.355020212022
Miller Lake44.816152-63.592737104.881764.5252.943.687619742020
Miller lake outlet44.807936-63.608131134.077124.6149.49.573020212022
Perry Lake44.797508-63.623780142.085124.1190.127.288920212022
Powder Mill Lake44.772213-63.606776236.707141.0267.542.835720182022
Second Lake44.784982-63.637725150.396134.3168.311.048020192022
Lake William Outlet44.785510-63.598820216.8812173.4417.889.868820212022
Lock Six44.940907-63.559285107.777103.1113.54.123020212022
Soldier Lake44.820965-63.572742109.385412.9190.937.551819832022
Third Lake44.787061-63.629808125.70882.8143.219.117720182022
Tillmann’s Brook44.825227-63.587153100.183155.9105.78.600220142017

Table 2 – 552 Samples with Specific Conductivity grouped and averaged at 25 locations within the watershed.

Figure 17. Distribution of SWEPS turbidity data

LocationLatLongTurbidity ntu AvgTurbidity ntu CountTurbidity ntu MinTurbidity ntu MaxTurbidity ntu St DevYear MinYear Max
A Lake44.823100-63.6288752.695070.9809.3602.970020212022
Annand Brook44.953745-63.5907494.265690.59025.6008.080720182022
Bennery Brook44.927000-63.5356603.7822821.10065.2008.813420192022
Black’s Brook44.822208-63.6191533.266760.70011.8504.267120212022
Charles Lake44.736123-63.5551775.780040.98012.6005.446620212022
First Lake44.776367-63.6736247.909261.64022.4007.369220182022
Fish Lake44.905371-63.5855611.782170.9404.0701.089020212022
Fletcher Lake44.841469-63.6120360.69781180.2106.4000.673219902022
Grand Lake44.909608-63.6029372.1432170.6204.8501.219820212022
Kinsac Lake44.828792-63.6542921.412970.7102.1900.456920182022
Lake Thomas44.801883-63.6080911.3954130.4004.4051.008820212022
Lake William44.773180-63.5901811.6122160.4905.5101.582520182022
Laurie Brook44.882825-63.5982584.977524.2205.7351.071320212022
Miller Lake44.816152-63.5927371.709260.6304.3001.384119832020
Miller lake outlet44.807936-63.6081311.107170.6451.8200.406120212022
Perry Lake44.797508-63.6237808.087051.54014.6004.704620212022
Powder Mill Lake44.772213-63.6067760.926760.5201.4000.322820182022
Second Lake44.784982-63.6377251.402560.7452.2550.644620192022
Lake William Outlet44.785510-63.5988201.6192120.5204.8501.127720212022
Lock Six44.940907-63.5592852.015860.5504.1101.352020212022
Soldier Lake44.820965-63.5727422.1836220.4406.6401.955419832022
Third Lake44.787061-63.6298081.102170.3802.2250.755120182022

Table 3 – 372 Samples with turbidity grouped and averaged at 22 locations within the watershed.

Figure 18. Distribution of SWEPS pH data

LocationLatLongPH AvgPH CountPH MinPH MaxPH Std DevYear MinYear Max
A Lake44.823100-63.6288756.8176.387.080.233120212022
Annand Brook44.953745-63.5907496.6595.707.130.494420182022
Bennery Brook44.927000-63.5356606.971035.539.930.433320182022
Black’s Brook44.822208-63.6191536.9766.517.350.307920212022
Charles Lake44.736123-63.5551777.4277.087.930.343320182022
First Lake44.776367-63.6736247.5377.348.000.235120182022
Fish Lake44.905371-63.5855616.9976.617.420.323120212022
Fletcher Lake44.841469-63.6120366.731454.507.750.388119902022
Grand Lake44.909608-63.6029377.16626.417.660.264720092022
Holland Brook44.847397-63.6037836.58245.687.320.418220132017
Kinsac Lake44.828792-63.6542927.0786.407.780.418720182022
Lake Loon44.711137-63.5156207.1926.957.420.332320182018
Lake Thomas44.801883-63.6080917.19156.707.950.373620212022
Fletcher Lake Outlet44.856700-63.6173507.13446.007.500.288020092017
Lake William44.773180-63.5901816.79455.148.160.672620182022
Laurie Brook44.882825-63.5982586.5926.276.900.445520212022
Miller Lake44.816152-63.5927376.10194.507.500.976819742020
Miller lake outlet44.807936-63.6081317.0076.607.490.371420212022
Perry Lake44.797508-63.6237807.1856.687.630.361420212022
Powder Mill Lake44.772213-63.6067767.7477.248.080.280520182022
Second Lake44.784982-63.6377257.2767.187.460.103820192022
Lake William Outlet44.785510-63.5988207.23126.847.490.221120212022
Lock Six44.940907-63.5592856.7496.027.280.379620212022
Soldier Lake44.820965-63.5727426.40564.177.880.745119832022
Third Lake44.787061-63.6298087.5687.047.920.308420182022
Tillmann’s Brook44.825227-63.5871536.58316.106.900.168520142017

Table 4 – 655 Samples with PH grouped and averaged at 26 locations within the watershed.

Figure 19. Distribution of SWEPS TDS data

LocationLatLongTDS ppm AvgTDS ppm CountTDS ppm MinTDS ppm MaxTDS ppm St DevYear MinYear Max
A Lake44.823100-63.62887568.25751.0075.408.139720212022
Annand Brook44.953745-63.59074928.19813.0043.5510.787120182022
Bennery Brook44.927000-63.535660177.7710326.20336.7088.719720182022
Black’s Brook44.822208-63.61915370.07663.5073.453.550220212022
Charles Lake44.736123-63.555177172.476157.30191.7512.088420182022
First Lake44.776367-63.673624361.486236.60461.5076.732620182022
Fish Lake44.905371-63.58556164.04761.7566.701.808220212022
Fletcher Lake44.841469-63.612036115.326110.50118.302.636820212022
Grand Lake44.909608-63.60293767.541713.0084.5014.590120212022
Kinsac Lake44.828792-63.65429271.09748.50151.4536.934220182022
Lake Loon44.711137-63.515620194.032172.90215.1529.875320182018
Lake Thomas44.801883-63.608091120.6115108.55141.009.120820212022
Lake William44.773180-63.59018199.651639.00137.1036.658220182022
Laurie Brook44.882825-63.59825868.23255.2581.2018.349420212022
Miller Lake44.816152-63.59273783.94570.85100.1012.772720182020
Miller lake outlet44.807936-63.60813187.62680.0096.856.687220212022
Perry Lake44.797508-63.62378091.24580.50121.5517.351120212022
Powder Mill Lake44.772213-63.606776162.656150.15173.807.712320182022
Second Lake44.784982-63.637725100.61495.55109.206.034120212022
Lake William Outlet44.785510-63.598820141.0712112.45273.0058.713420212022
Lock Six44.940907-63.55928570.56767.6074.102.343020212022
Soldier Lake44.820965-63.57274287.881963.70152.1024.153020182022
Third Lake44.787061-63.62980886.57676.7093.005.548720182022

Table 5 – 280 Samples with TDS grouped and averaged at 23 locations within the watershed.

Total phosphorus had some very high nutrient locations from the AECOM report and East Hants data. In particular, the largest value, located on the West side of the map in Figure 20, was from a previous sewage plant, and this lake is now considered dead (Tom Mills). Other high phosphorus areas could have been results from effluent, farms, or possibly septic tanks. The average TKN values from the 5 East Hants sites, were all very close to 1 mg/L, so they did not have much variation and would not show any noticeable variation if mapped. 

Figure 20. Distribution of phosphorus data from AECOM report and East Hants spreadsheet

LIDAR Data

Knowing the extent of the watershed and seeing the LIDAR imaging of the watershed may help with future characterization and analysis. Cam has suggested stitching the HRM LIDAR data seen below in Figure 21 to the East Hants LIDAR data to complete the pictures, since the top of Grand Lake is missing from this data. This could be a task for future students.

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Figure 21. LIDAR imaging with SWEPS test sites

Summary and Recommendations

There are very evident patterns in the temporal and spatial visualizations of the SWEPS data, though it is important to note the quality of the data, such as how many data points were taken and what the years of those points were. These concerns could be tackled by future students. The readings from the airport culvert under the highway were very high when observed in the field and may not have been in the data, which should be investigated. First Lake also had very high readings for one data point, which, in field observations, was likely from the loads of cut grass and plant debris that has washed up on shore after a big rain. This is an outlier that may need discussion if it needs to be taken out of the map data. This data is full of trends that may interest students, the SWEPS committee, and other parties. This report can be used as a starting point for a more in-depth analysis of the watershed. All materials used can be found in the 2022 SWEPS files.

As for predicting blue-green algae blooms, it would be very difficult to predict blooms since blooms were reported across the watershed and SWEPS does not have the specific locations, especially for larger lakes. Regardless, this information can still be used for the Bennery Brook project and focusing on restoration for other areas as well, and can still identify “problem” areas.

The following are suggestions for future students to continue work on this data:

  • Implement the 2022 phosphorus and nitrogen SWEPS data from AGAT
  • For a more detailed map, more specific coordinates can be found for each site, so sites won’t be grouped and averaged into one value and the proper location can be displayed
  • Investigate the data of the elevated parameter areas to see if there is any change over time.
  • Investigate outliers for the number of data points and dates of data points
  • Investigate airport culvert readings
  • Discuss if First Lake reading should be taken out of map data
  • Stitch East Hants and HRM LIDAR
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