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Sherbrooke Lake
2019 Water Quality Monitoring Report
Prepared for
Municipality of Chester
Municipality of the District of Lunenburg
Sherbrooke Lake Stewardship Committee
By
Coastal Action
37 Tannery Road, PO Box 730
Lunenburg, N.S.
B0J 2C0
December 2019
II
Table of Contents
Executive Summary .................................................................................................................................... VIII
1. Introduction .......................................................................................................................................... 1
1.1. Sherbrooke Lake Background ....................................................................................................... 1
1.2. Program Background .................................................................................................................... 2
1.3. Review of the 2018 Sherbrooke Lake Water Quality Monitoring Report ..................................... 2
1.4. Changes to the 2019 Sherbrooke Lake Water Quality Monitoring Program ................................ 3
1.5. Objectives and Scope of Work ...................................................................................................... 6
2. Sherbrooke Lake Monitoring Results .................................................................................................... 6
2.1. Sherbrooke Lake Weather ............................................................................................................ 6
2.2. Physical Water Parameters ........................................................................................................... 8
2.2.1. Surface Water Temperature ................................................................................................. 8
2.2.2. Surface Dissolved Oxygen ..................................................................................................... 9
2.2.3. Depth Profiles...................................................................................................................... 11
2.2.4. pH ........................................................................................................................................ 14
2.2.5. Total Dissolved Solids .......................................................................................................... 17
2.3. Chemical Water Parameters ....................................................................................................... 19
2.3.1. Total Suspended Solids ....................................................................................................... 19
2.3.2. Total Phosphorus ................................................................................................................ 21
2.3.3. Total Nitrogen ..................................................................................................................... 24
2.3.4. Chlorophyll a ....................................................................................................................... 26
2.3.5. E. Coli Bacteria .................................................................................................................... 28
2.4. Sediment Sampling ..................................................................................................................... 31
2.4.1. Metals ................................................................................................................................. 31
2.4.2. Hydrocarbons ...................................................................................................................... 34
2.4.3. Nutrients ............................................................................................................................. 35
3. Discussion ............................................................................................................................................ 35
3.1. Trophic State of Sherbrooke Lake ............................................................................................... 35
3.2. Algal Blooms ................................................................................................................................ 37
3.3. Pollution ...................................................................................................................................... 39
4. Recommendations .............................................................................................................................. 40
5. References .......................................................................................................................................... 41
III
List of Figures
Figure 1: Left - Streams (yellow) and drainage boundary (red) of Sherbrooke Lake. Right – Bathymetry of
Sherbrooke Lake and proposed public access site (red circle). .................................................................... 1
Figure 2: Sherbrooke Lake 2019 Water Quality Monitoring Program sampling locations. Crossed out
sampling sites represent discontinued sampling sites; Chl 1 and Chl 2 were discontinued for the 2019
program. ....................................................................................................................................................... 4
Figure 3: Daily air temperature data at Sherbrooke Lake, from May-October 2019. .................................. 7
Figure 4: Daily accumulated rainfall at Sherbrooke Lake, NS from May-October 2019. Rainfall data from
August 27th was removed and labelled a misread by the weather station, and data was added to
September 8th to account for rainfall which fell when the station went offline during Hurricane Dorian. . 7
Figure 5: Water temperatures at four monthly lake sites (Lake 1-4) during the May-October 2019 SL
water quality field season. Red line indicates the 20oC limit for survival of aquatic organisms. ................. 8
Figure 6: Water temperatures at four bimonthly and rainfall-dependent stream sites (Sherbrooke River,
Forties River, Pine Lake, and Zwicker Brook), in addition to three rainfall-dependent stream sites (Butler
Lake Brook, Gully River, and Peter Veinot Brook), during the May-October 2019 SL water quality field
season. Red line indicates the 20oC limit for survival of aquatic organisms. ................................................ 9
Figure 7: DO at four monthly lake sites (Lake 1-4) during the May-October 2019 SL water quality field
season. Red line indicates CCME’s 6.5 mg/L DO minimum-threshold for survival of aquatic organisms. . 10
Figure 8: DO at four bimonthly and rainfall-dependent stream sites (Sherbrooke River, Forties River, Pine
Lake, and Zwicker Brook), in addition to three rainfall-dependent stream sites (Butler Lake Brook, Gully
River, and Peter Veinot Brook). Red line indicates CCME’s 6.5 mg/L DO minimum-threshold for survival
of aquatic organisms. .................................................................................................................................. 10
Figure 9: Water temperature depth profiles from two lake sites sampled in August 2018 (blue) and 2019
(green). Red line indicates the 20oC limit for survival of aquatic organisms. ............................................. 12
Figure 10: DO depth profiles from two lake sites sampled in August 2018 (blue) and 2019 (green). Red
line indicates CCME’s 6.5 mg/L DO minimum-threshold for survival of aquatic organisms. ..................... 13
Figure 11: Four common water temperature and DO depth profiles, from Hutchinson, 1957. ................ 14
Figure 12: pH at four monthly lake sites (Lake 1-4) during the May-October 2019 SL water quality field
season. Red line indicates the 5.0-pH minimum threshold for survival of fish and invertebrates (Morris,
Taylor, and Brown, 1989). ........................................................................................................................... 16
Figure 13: pH at four bimonthly and rainfall-dependent stream sites (Sherbrooke River, Forties River,
Pine Lake, and Zwicker Brook), in addition to three rainfall-dependent stream sites (Butler Lake Brook,
Gully River, and Peter Veinot Brook), during the May-October 2019 SL water quality field season. Red
line indicates the 5.0-pH minimum threshold for survival of fish and invertebrates (Morris, Taylor, and
Brown, 1989). .............................................................................................................................................. 16
Figure 14: TDS at four monthly lake sites (Lake 1-4) during the May-October 2019 SL water quality field
season. ........................................................................................................................................................ 18
IV
Figure 15: TDS at four bimonthly and rainfall-dependent stream sites (Sherbrooke River, Forties River,
Pine Lake, and Zwicker Brook), in addition to three rainfall-dependent stream sites (Butler Lake Brook,
Gully River, and Peter Veinot Brook), during the May-October 2019 SL water quality field season. ........ 19
Figure 16: TSS at three monthly lake sites (Lake 1, 2, and 4) during the May-October 2019 SL water
quality field season. As Lake 3 only sampled bacteria in 2019, no data are available for 2019 and
therefore Lake 3 is not included. ................................................................................................................ 20
Figure 17: TSS at four bimonthly and rainfall-dependent stream sites (Sherbrooke River, Forties River,
Pine Lake, and Zwicker Brook), in addition to three rainfall-dependent stream sites (Butler Lake Brook,
Gully River, and Peter Veinot Brook), during the May-October 2019 SL water quality field season. ........ 21
Figure 18: Total phosphorus at three monthly lake sites (Lake 1, 2, and 4) during the May-October 2019
SL water quality field season. Red line indicates the MOECC 0.02 mg/L guideline for phosphorus in lakes.
As Lake 3 only sampled bacteria in 2019, no data are available for nutrients and therefore Lake 3 is not
included. ...................................................................................................................................................... 22
Figure 19: Total phosphorus at four bimonthly and rainfall-dependent stream sites (Sherbrooke River,
Forties River, Pine Lake, and Zwicker Brook), in addition to three rainfall-dependent stream sites (Butler
Lake Brook, Gully River, and Peter Veinot Brook), during the May-October 2019 SL water quality field
season. Red line indicates the MOECC 0.03 mg/L guideline for phosphorus in streams. .......................... 23
Figure 20: Total nitrogen at three monthly lake sites (Lake 1, 2, and 4) during the May-October 2019 SL
water quality field season. Red solid line indicates the Dodds and Welch (2000) 0.9 mg/L nitrogen
threshold for freshwaters, and red dashed line indicates the Underwood and Josselyn (1979) 0.3 mg/L
nitrogen threshold for oligotrophic lakes. As Lake 3 only sampled bacteria in 2019, no data are available
for nutrients and therefore Lake 3 is not included. .................................................................................... 25
Figure 21: Total nitrogen at four bimonthly and rainfall-dependent stream sites (Sherbrooke River,
Forties River, Pine Lake, and Zwicker Brook), in addition to three rainfall-dependent stream sites (Butler
Lake Brook, Gully River, and Peter Veinot Brook), during the May-October 2019 SL water quality field
season. Red line indicates the Dodds and Welch (2000) 0.9 mg/L nitrogen threshold for freshwaters. ... 25
Figure 22: Chlorophyll a at three monthly lake sites (Lake 1, 2, and 4) during the May-October 2019 SL
water quality field season. As Lake 3 only sampled bacteria in 2019, no data are available for chlorophyll
a and therefore Lake 3 is not included. ...................................................................................................... 27
Figure 23: Chlorophyll a at four bimonthly and rainfall-dependent stream sites (Sherbrooke River, Forties
River, Pine Lake, and Zwicker Brook), in addition to three rainfall-dependent stream sites (Butler Lake
Brook, Gully River, and Peter Veinot Brook), during the May-October 2019 SL water quality field season.
.................................................................................................................................................................... 28
Figure 24: E. coli at four monthly lake sites (Lake 1-4) during the May-October 2019 SL water quality field
season. Red solid line indicates Health Canada’s primary limit for recreation in freshwaters (400 CFU/100
mL), and red dashed line indicates Health Canada’s secondary limit for recreation in freshwaters (1,000
CFU/100 mL). .............................................................................................................................................. 30
Figure 25: E. coli at four bimonthly and rainfall-dependent stream sites (Sherbrooke River, Forties River,
Pine Lake, and Zwicker Brook), in addition to three rainfall-dependent stream sites (Butler Lake Brook,
Gully River, and Peter Veinot Brook), during the May-October 2019 SL water quality field season. Red
V
solid line indicates Health Canada’s primary limit for recreation in freshwaters (400 CFU/100 mL), and
red dashed line indicates Health Canada’s secondary limit for recreation in freshwaters (1,000 CFU/100
mL). ............................................................................................................................................................. 30
Figure 26: Carlson TSI for lakes, with TSI ranks for SL Lake 1 (red star), Lake 2 (blue star), and Lake 4
(yellow star). Transparency determined using Secchi disk depth. From Carlson (1977)............................ 37
Figure 27: Reported algae bloom locations (green triangles) within Sherbrooke Lake during the 2019
field season. ................................................................................................................................................ 38
VI
List of Tables
Table 1: Monitoring program parameters, site locations, and sampling frequencies for the 2019
Sherbrooke Lake Water Quality Monitoring Program. GPS coordinates to access river sites via road are in
blue. .............................................................................................................................................................. 5
Table 2: Mean DO concentrations for the four lake sites and seven stream sites of the Sherbrooke Lake
Monitoring Program for the 2018 and 2019 field seasons. ........................................................................ 11
Table 3: Mean pH for the four lake sites and seven stream sites of the Sherbrooke Lake Monitoring
Program for the 2018 and 2019 field seasons. ........................................................................................... 17
Table 4: Mean and maximum TDS concentrations from lake and river sites during the 2018 and 2019 SL
field seasons. ............................................................................................................................................... 18
Table 5: Mean TSS concentrations from lake and river sites during the 2018 and 2019 SL field seasons. As
Lake 3 only sampled bacteria in 2019, no data are available for TSS for 2019. ......................................... 20
Table 6: Maximum and mean Secchi disk depths from lake sites during the 2018 and 2019 SL field
seasons. No maximum Secchi depth is available for Lake 3 and 4, as both are visible down to their site’s
lake bottom. ................................................................................................................................................ 21
Table 7: Range in total phosphorus concentrations between 2018 and 2019; July-September for lake and
stream samples. As Lake 3 only sampled bacteria in 2019, no data are available for total phosphorus for
2019. ........................................................................................................................................................... 23
Table 8: Total phosphorus concentrations from two lake sites, obtained both at the surface and below
the thermocline, taken in August for the SL 2018 and 2019 Water Quality Monitoring Programs, in
addition to orthophosphate concentrations taken below the thermocline in 2019. ................................. 24
Table 9: Range in total nitrogen concentrations between 2018 and 2019; July-September for lake and
stream samples. As Lake 3 only sampled bacteria in 2019, no data are available for total nitrogen for
2019. ........................................................................................................................................................... 26
Table 10: Total nitrogen concentrations from two lake sites, obtained both at the surface and below the
thermocline, in August for the SL 2018 and 2019 Water Quality Monitoring Programs. .......................... 26
Table 11: Maximum and mean chlorophyll a from lake and river sites during the 2018 and 2019 SL field
seasons. As Lake 3 only sampled bacteria in 2019, no data are available for chlorophyll a for 2019........ 28
Table 12: Concentration of metals within site sediment samples sampled on August 27th, 2018 and
August 11th, 2019. Interim sediment quality guideline (ISQG) is the recommendation by CCME of total
concentrations of chemicals in surficial sediment, while the probable effect level (PEL) is the CCME
upper value in which adverse effects are expected (CCME, 2001). Nova Scotia environmental quality
standards (NSEQS) are sediment guidelines specifically set by the Nova Scotia Environment (NSE, 2014).
Light yellow indicates parameters approaching one of the guidelines, while dark yellow indicates an
exceedance of one of the guidelines. ......................................................................................................... 33
Table 13: Comparison of 2018 and 2019 sediment metal concentrations from SL lake and river sites to
the range and mean metal concentrations from four Kejimkujik Lakes (Hilchemakaar, Big Dam East,
Cobrielle, and Peskowesk) monitored from 2000-2009 (Kirk, 2018). ......................................................... 34
VII
Table 14: Phosphorus concentrations in sediment samples from lake and river sites sampled on August
27th, 2018, and August 11th, 2019. .............................................................................................................. 35
Table 15: Carlson (1977) 2018 and 2019 SL TSI scores and trophic states for total phosphorus,
chlorophyll A, and Secchi disk for Lake 1 (red), Lake 2 (blue), and Lake 4 (yellow – for 2019 only). ......... 36
VIII
Executive Summary
Water quality has been monitored at Sherbrooke Lake since 2017, in response to concerns regarding the
development of a public access site and the increased recreational usage of the lake. The Sherbrooke
Lake Stewardship Committee was created by both the Municipality of the District of Lunenburg and the
Municipality of Chester. This committee oversees the Sherbrooke Lake Monitoring Program which is
managed by Coastal Action and executed by committee members and trained volunteers. The 2019 field
season represents the second of five years of planned monitoring.
Water temperatures for the lakes and streams pose minimal threat to aquatic life. Water temperatures
exceeded the recommended 20oC thermal threshold for cold-water fish once – in August. No stream
sites exceeded the temperature threshold. A thermocline formed at both Lake 1 and Lake 2 sites during
the summer months, with deeper waters providing thermal refuge for organisms; however, the
thermocline present at Lake 1 was minimal, with only 3.9oC difference between surface and bottom
waters.
Dissolved oxygen concentrations for Sherbrooke Lake and its tributaries were within acceptable ranges
for aquatic life. No lake or stream site fell below the 6.5 mg/L Canadian Council of Ministers of the
Environment (CCME) minimum requirement for aquatic life. The thermocline present at Lake 1 and Lake
2 did result in the stratification of oxygen. Lake 1’s weak thermocline resulted in higher dissolved oxygen
within the profile, with hypoxic conditions occurring below 1 m depth, while Lake 2 displayed reductions
in dissolved oxygen throughout the depth profile with hypoxic conditions beginning 10-m above the lake
bottom.
pH in Sherbrooke Lake does not pose a risk to aquatic organisms and appears to buffer the acidity of the
seven monitored tributaries. Although no lake sites had pH measurements below CCME’s 6.5-pH
minimum threshold, all stream sites fell below this guideline. In September 2019, several sites fell below
the 5.0-pH threshold for the protection of fish eggs, which may impact native fish species using these
headwater streams for spawning.
Nutrients in Sherbrooke Lake were below suggested thresholds; however, concentrations have
increased since 2018. Total phosphorus concentrations fell below Ontario’s Ministry of Environment and
Climate Change (MOECC) guideline of 0.02 mg/L at all lake sites, and all but one stream sample. All lake
and stream sites fell below the 0.9 mg/L Dodds & Welch (2000) threshold for freshwater environments,
with only one lake sample exceeding the 0.3 mg/L threshold for oligotrophic lakes (Underwood and
Josselyn, 1979). Although phosphorus concentrations at depth were equal to or higher than surface
water concentrations, the ratio of bioavailable orthophosphate was low, limiting the potential for
internal loading. Similarly, nitrogen concentrations at-depth were below those measured at the surface,
indicating minimal risk for nutrient enrichment during the lake turnover. Both nitrogen and phosphorus
concentrations increased in the tributary streams following the Hurricane Dorian rainfall event;
however, the elevated concentrations did not appear to impact lake water quality, as no lake
concentrations increased.
E. coli concentrations fell below both primary and secondary Health Canada (2012) recreational limits
within the lake, but not its tributaries. No lake sites had more than 20 CFU/100 mL of E. coli, well below
IX
the 400 CFU/100 mL and 1000 CFU/100 mL primary and secondary thresholds, respectively. Stream sites
fell below both thresholds for all except one sample – 720 CFU/100 mL at Pine Lake Brook in September.
The exceedance of Pine Lake Brook’s bacteria sample coincided with other elevated bacteria
concentrations from other sites due to the Hurricane Dorian rainfall event. Although all streams
displayed elevated E. coli concentrations, no negative effects were observed at the lake sites, as no site
exceeded 20 CFU/100 mL. Flushing of pollutants into nearby waterways is common following heavy
rainfall events.
Sediment collected from Lake 1, Lake 2, Lake 4, and Zwicker Brook indicated a moderate level of
contamination. All three lake sites exceeded CCME arsenic and cadmium guidelines, with Lake 1 also
exceeding mercury guidelines, and Lake 2 exceeding mercury and manganese guidelines. Zwicker Brook
did not exceed any metal guidelines.
Sherbrooke Lake’s low productivity places it along the oligotrophic-mesotrophic boundary. This trophic
status is the same as 2018; however, nutrient concentrations and the frequency of algal bloom reporting
have increased in 2019. Continued water quality monitoring is necessary to track changes within the
lake, in coordination with an educational component and a communications plan.
1
1. Introduction
1.1. Sherbrooke Lake Background
Sherbrooke Lake (SL) is located in the headwaters of the LaHave River watershed, in Southern Nova
Scotia. Sherbrooke Lake covers 16.94 km2 – the largest waterbody within the LaHave watershed – and
has a 285 km2 drainage basin (Figure 1). Although SL is fed by 14 inlet streams, many are less than 1 km
in length. Sherbrooke River is the largest inlet stream feeding SL, while North Branch is the only outlet
stream of the lake - located on the southwest side of the lake.
The water quality of the LaHave River watershed has been monitored by Coastal Action since 2007. The
program monitors 15 sites throughout the watershed, including the Sherbrooke River which feeds the
lake, and the lake’s outlet downstream. A water quality index (WQI) report card on the status of the
watershed and the individual sites is reported annually and available on the Coastal Action website
(www.coastalaction.org).
Forestry, silviculture, and agriculture dominate the LaHave River watershed and SL drainage area. Rural
communities are also located throughout, with cottages and camps found along the edge of SL.
Figure 1: Left - Streams (yellow) and drainage boundary (red) of Sherbrooke Lake. Right – Bathymetry of Sherbrooke Lake and
proposed public access site (red circle).
2
In 2015, the Municipality of the District of Lunenburg (MODL) began investigating ways to allow public
access to the lake by appointing the Sherbrooke Lake Access Advisory Committee (SLAAC). SLAAC was to
present options for accessing SL, and to obtain community advice and input throughout the process.
After public consultations, held by UPLAND Planning + Design, a section of land on the south-eastern
side of the lake was selected for the public access site (Figure 1). In the report provided to SLAAC by
UPLAND Planning + Design, the implementation of a water quality committee for Sherbrooke Lake was
recommended.
1.2. Program Background
As a result of the planned public access site at SL, the Sherbrooke Lake Stewardship Committee (SLSC)
was formed. The SLSC, a joint commitment between MODL and the Municipality of Chester (MOC), is
comprised of one Coastal Action staff, two residents of MODL, two residents of MOC, a water quality
expert, and supporting municipal staff. The SLSC was tasked with developing and implementing a water
quality monitoring program to: determine a baseline understanding of water quality conditions within SL
prior to construction of the public access site, monitor water quality during and after the construction,
and provide evidence-based advice to MODL and MOC regarding ways to address water quality changes
and concerns within the lake.
The SLSC developed a water quality monitoring program to track the baseline and changes in water
quality conditions within SL. Coastal Action acts as technical support for a set of trained volunteers, who
conduct the monthly and rainfall-dependent sampling for the program. Although a preliminary
monitoring program was implemented in 2017, the full Sherbrooke Lake Water Quality Monitoring
Program was conducted in 2018 and 2019.
Further details on the program can be found in the Sherbrooke Lake Water Quality Monitoring Program,
and previous program results are found in the Sherbrooke Lake Water Quality Monitoring Report (2018);
all are available upon request from either the Municipality of Chester or the Municipality of the District
of Lunenburg.
1.3. Review of the 2018 Sherbrooke Lake Water Quality Monitoring Report
The trophic state of SL in 2018 was calculated for two different sites: Lake 1 and Lake 2. Both had a
trophic state of borderline oligotrophic-mesotrophic. The borderline status indicates that the lake has
low phosphorus concentrations but has a moderate presence of biological activity and, therefore,
remains vulnerable to outside influences which may degrade water quality.
Thermal and oxygen profiles were conducted at both Lake 1 and Lake 2 sites. Thermal stratification of
the lake was observed at Lake 2, with a weak thermocline at Lake 1. Due to the presence a thermocline,
stratification of dissolved oxygen was also observed at both sites. Depletion of oxygen in the deeper
waters at both locations indicates minimal mixing between surficial and deep waters, with
concentrations less than 2 mg/L in the bottom waters posing a threat to aquatic organisms.
3
Nutrients in SL fell below literature guidelines for both nitrogen and phosphorus for most samples.
Stream sites had higher concentrations of both nutrients, indicating nutrient loading from surrounding
sources. Spikes in nutrients and bacteria following rainfall events highlight the role of overland flow in
flushing nutrients and bacteria from nearby sources into the streams and lake.
Concentrations of metals within the lake sediment exceeded Nova Scotia guidelines. Arsenic, cadmium,
lead, and mercury exceeded their guidelines, with manganese and selenium approaching their
respective thresholds. Continued sediment monitoring was recommended to monitor metal
concentrations and changes in loading to the lake as development continues.
1.4. Changes to the 2019 Sherbrooke Lake Water Quality Monitoring Program
Several changes were applied to the Water Quality Monitoring Program for the 2019 season (Figure 2,
Table 1):
• A weather station was installed on a private property at Sherbrooke Lake, to monitor the lake’s
microclimate.
• The Fecal Indicator Bacteria species was switched from fecal coliform to Escherichia coli (E. coli)
at all sites to adhere to Health Canada standards for bacteria monitoring in freshwaters.
• Two summer-only sites (Chl 1 and Chl 2) were dropped from the sampling program.
• Sediment sampling was added to the monitoring program for Lake 1.
• Sediment sampling was to be rotated annually to capture concentrations from all seven primary
inlet streams, with 2019 sampling at Zwicker Brook.
• Hydrocarbon sampling was removed from the monthly lake water samples and added to the list
of parameters in the one-time sediment samples.
• All water chemistry parameters, except for E. coli, were removed from sampling at Lake 3.
• Lake 4 was upgraded to a full site, tested monthly for E. coli, total suspended solids (TSS),
nutrients (nitrogen and phosphorus), and physical water parameters (using the multi-parameter
YSI probe and a Secchi disk).
• As the rainfall sampling and September sampling occurred on the same day, the September
bimonthly stream sites were not sampled as to avoid duplication from the rainfall-dependent
stream samples. The costs for four saved samples were used to offset the costs of Coastal Action
staff installing the Sherbrooke Lake weather station.
• A communications plan was added to the program to help share results and encourage
conservation and protection of local waterbodies. The communications plan included:
o A full technical 2019 Sherbrooke Lake Water Quality Monitoring Report.
o A brief two-page overview of the 2019 Sherbrooke Lake Water Quality Monitoring
Report.
o A Frequently Asked Questions document regarding the SLSC and the monitoring
program.
o An article to be included in the Municipal Matters and Municipal Insight newsletters.
o A Carolyn’s Corner article to be included in the South Shore Breaker.
4
o An article to be included in Coastal Action’s quarterly Coastal Chronicle newsletter.
o Various social media posts to be shared by the MOC, MODL, and Coastal Action.
Figure 2: Sherbrooke Lake 2019 Water Quality Monitoring Program sampling locations. Crossed out sampling sites represent
discontinued sampling sites; Chl 1 and Chl 2 were discontinued for the 2019 program.
5
Table 1: Monitoring program parameters, site locations, and sampling frequencies for the 2019 Sherbrooke Lake Water Quality
Monitoring Program. GPS coordinates to access river sites via road are in blue.
Sample Site
Name
Site Coordinates
(UTM Zone 20T)
Sampling Frequency Parameters Sampled
Lake 1 372287 E, 4947688 N Monthly (May-Oct.) YSI+, hydrocarbons, total suspended solids, total
phosphorus, total nitrogen, E. Coli, chlorophyll a,
Secchi disk depth. One-time depth profile,
nutrients at-depth, and sediment grab.
Lake 2 376072 E, 4943018 N Monthly (May-Oct.) YSI, hydrocarbons, total suspended solids, total
phosphorus, total nitrogen, E. Coli, chlorophyll a,
Secchi disk depth. One-time depth profile,
nutrients at-depth, and sediment grab.
Lake 3
(Public
Access)
376831 E, 4943540 N Monthly (May-Oct.) YSI, E. Coli, Secchi disk depth.
Lake 4
(Public
Access Boat
Launch)
376844 E, 4943371 N Monthly (Sept-Oct.) YSI, hydrocarbons, total suspended solids, total
phosphorus, total nitrogen, E. Coli, chlorophyll a.
One-time depth profile and sediment grab.
Butler Lake
Brook
370079 E, 4952036 N One-time, rainfall-
dependent
YSI, total suspended solids, total phosphorus,
total nitrogen, E. Coli, chlorophyll a.
Sherbrooke
River
369774 E, 4954072 N Bi-monthly (May,
July, Sept.) &
rainfall-dependent
YSI, total suspended solids, total phosphorus,
total nitrogen, E. Coli, chlorophyll a.
Gully River 372246 E, 4953404 N One-time, rainfall-
dependent
YSI, total suspended solids, total phosphorus,
total nitrogen, E. Coli, chlorophyll a.
Forties River 373539 E, 4949823 N Bi-monthly (May,
July, Sept.) &
rainfall-dependent
YSI, total suspended solids, total phosphorus,
total nitrogen, E. Coli, chlorophyll a.
Pine Lake
Brook
373705 E, 4945670 N Bi-monthly (May,
July, Sept.) &
rainfall-dependent
YSI, total suspended solids, total phosphorus,
total nitrogen, E. Coli, chlorophyll a.
Zwicker
Brook
376582 E, 4944469 N Bi-monthly (May,
July, Sept.) &
rainfall-dependent
YSI, total suspended solids, total phosphorus,
total nitrogen, E. Coli, chlorophyll a. One-time
dept profile and sediment grab.
Peter Veinot
Brook
376507 E, 4941558 N One-time, rainfall-
dependent
YSI, total suspended solids, total phosphorus,
total nitrogen, E. Coli, chlorophyll a.
+YSI is a multi-parameter water quality device that measures the physical characteristics (temperature, dissolved oxygen, pH, total dissolved
solids, salinity, pressure, and specific conductivity) of the water at the time of sampling.
6
1.5. Objectives and Scope of Work
The objective of this program is to provide a water quality overview for Sherbrooke Lake, which can help
the SLSC provide evidence-based advice to both MODL and MOC. Within the SLSC, Coastal Action’s
scope of work included:
● Designing and writing the Sherbrooke Lake 2019 Water Quality Monitoring Program;
● Ordering and ensuring correct sampling bottles and analysis from Maxxam Analytics;
● Creating and printing waterproof field sheets for each sampling month;
● Ordering and installing a weather station at Sherbrooke Lake;
● Ordering and downloading sampling locations to a new GPS;
● Calibrating and caring for the MODL/MOC-owned YSI monthly;
● Ensuring volunteers obtained all required field equipment for field work;
● Organizing algal bloom sampling as needed with volunteers, Nova Scotia Environment;
● Conducting one-time field sediment and nutrient at-depth sampling with volunteers;
● Transferring data from field sheets and Maxxam into a database and analyzing data;
● Downloading and analyzing weather data from the Sherbrooke Lake weather station;
● Attending SLSC meetings and presenting water quality results;
● Writing communications regarding the Sherbrooke Lake Water Quality Monitoring Program and
its results; and
● Preparing this report to summarize results and recommendations for water quality related to
Sherbrooke Lake.
2. Sherbrooke Lake Monitoring Results
2.1. Sherbrooke Lake Weather
Following the installation of a weather station at Sherbrooke Lake, the microclimate conditions at
Sherbrooke Lake were monitored from May 15 to October 11, 2019. Air temperatures at Sherbrooke
Lake ranged from -0.5oC to 33.1oC (Figure 3). Minimal rainfall accumulated at the lake during the hottest
months – July and August (Figure 4). The largest rainfall occurred on September 8, 2019 during
Hurricane Dorian, with >100 mm rainfall falling within 36 hours. As the weather gauge is protected on
two sides by forest, wind speed and direction are considered skewed and are not included in this report.
7
Figure 3: Daily air temperature data at Sherbrooke Lake, from May-October 2019.
Figure 4: Daily accumulated rainfall at Sherbrooke Lake, NS from May-October 2019. Rainfall data from August 27th was
removed and labelled a misread by the weather station, and data was added to September 8th to account for rainfall which fell
when the station went offline during Hurricane Dorian.
0
5
10
15
20
25
30
35
2019-05-15 2019-06-15 2019-07-15 2019-08-15 2019-09-15Air Temperature (oC)0
20
40
60
80
100
120
2019-05-15 2019-06-15 2019-07-15 2019-08-15 2019-09-15Accumulated Daily Rainfall (mm)
8
2.2. Physical Water Parameters
2.2.1. Surface Water Temperature
Water temperature is a key parameter in understanding and assessing the health and productivity of an
aquatic environment, as it directly impacts organisms, while also affecting other physical and chemical
parameters. Water temperature can impact the presence and survival of fish, where temperatures
outside of a species’ optimal range can negatively affect fish survival (NSSA, 2014); 20oC is the maximum
acceptable temperature for salmon and trout (Alabaster and Lloyd, 1982). In addition, increased water
temperature decreases a waterbody’s capacity to hold oxygen, thereby limiting available oxygen to
aquatic organisms.
In the lake sites, temperatures ranged from 9.0-23.2oC, while streams ranged from 7.4-16.3oC (Figures 5
and 6). The lake sites only exceeded 20oC during August 2019, while the stream sites never exceeded
20oC during the 2019 monitoring period. Lake temperatures have remained comparable to 2018 values;
stream temperatures have fallen compared to the 2018 values. Sherbrooke and Forties River had the
highest recorded water temperatures in 2018, with exceedances of 20oC occurring in both July and
August. Although no streams were measured in August 2019, both Sherbrooke and Forties River were at
least 3.7oC lower in July 2019 compared to their July 2018 counterparts. The shift in 2019 data towards
cooler temperatures may be explained by the earlier start of sampling – sampling at the beginning of
each month instead of the end – and collecting the rainfall-dependent sample in September rather than
August. These two changes resulted in minimal summer sampling, with no sampling during the hottest
period of the summer (no sampling was conducted in August), skewing the data to represent cooler
conditions.
Figure 5: Water temperatures at four monthly lake sites (Lake 1-4) during the May-October 2019 SL water quality field season.
Red line indicates the 20oC limit for survival of aquatic organisms.
0.0
5.0
10.0
15.0
20.0
25.0
05-Apr-19 05-May-19 04-Jun-19 04-Jul-19 03-Aug-19 02-Sep-19 02-Oct-19 01-Nov-19Water Temperature (oC)Lake 1 Lake 2 Lake 3 Lake 4
9
Figure 6: Water temperatures at four bimonthly and rainfall-dependent stream sites (Sherbrooke River, Forties River, Pine Lake,
and Zwicker Brook), in addition to three rainfall-dependent stream sites (Butler Lake Brook, Gully River, and Peter Veinot Brook),
during the May-October 2019 SL water quality field season. Red line indicates the 20oC limit for survival of aquatic organisms.
2.2.2. Surface Dissolved Oxygen
Dissolved oxygen (DO) is another key physical water parameter, as it is required for the survival of
aquatic organisms and affects how nutrients are cycled and released within lake waterbodies. The
Canadian Council of Ministers of the Environment (CCME) set a guideline of ≥6.5 mg/L for the protection
of aquatic life for cold-water species – species found in lakes such as Sherbrooke (CCME, 1999). DO not
only affects aquatic organisms but is also controlled by organisms (due to consumption), water
temperature, and the waterbody’s ability to mix and engulf DO (wind and waves increase dissolved
oxygen into the water).
No lake or stream site dropped below the 6.5 mg/L CCME aquatic threshold during the 2019 field season
(Figures 7 and 8). DO concentrations drop throughout the summer, at both lake and stream sites,
coinciding with increased biological demand. DO concentrations are higher than in 2018 (Table 2),
possibly a skewed trend due to a shift in sampling timing, which captured cooler periods which would
have higher oxygen dissolution capacity. Although it appears that Lake 3 is the only site where 2018
values are higher than 2019 values, this is misleading, as the site was only added in fall 2018 and
therefore the 2018 mean does not represent the full 2018 year. In addition, as Butler Lake Brook, Gully
River, and Peter Veinot Brook are rainfall-dependent samples, their mean values are not representative
of the entire field season as they are only sampled once per season.
0
5
10
15
20
25
05-Apr-19 05-May-19 04-Jun-19 04-Jul-19 03-Aug-19 02-Sep-19 02-Oct-19 01-Nov-19Water Temperature (oC)Sherbrooke River Forties River Pine Lake Brook Zwicker Brook
Butler Lake Brook Gully River Peter Veinot Brook
10
Figure 7: DO at four monthly lake sites (Lake 1-4) during the May-October 2019 SL water quality field season. Red line indicates
CCME’s 6.5 mg/L DO minimum-threshold for survival of aquatic organisms.
Figure 8: DO at four bimonthly and rainfall-dependent stream sites (Sherbrooke River, Forties River, Pine Lake, and Zwicker
Brook), in addition to three rainfall-dependent stream sites (Butler Lake Brook, Gully River, and Peter Veinot Brook). Red line
indicates CCME’s 6.5 mg/L DO minimum-threshold for survival of aquatic organisms.
0
2
4
6
8
10
12
14
05-Apr-19 05-May-19 04-Jun-19 04-Jul-19 03-Aug-19 02-Sep-19 02-Oct-19 01-Nov-19Dissolved Oxygen (mg/L)Lake 1 Lake 2 Lake 3 Lake 4
0
2
4
6
8
10
12
14
05-Apr-19 05-May-19 04-Jun-19 04-Jul-19 03-Aug-19 02-Sep-19 02-Oct-19 01-Nov-19Dissolved Oxygen (mg/L)Sherbrooke River Forties River Pine Lake Brook Zwicker Brook
Butler Lake Brook Gully River Peter Veinot Brook
11
Table 2: Mean DO concentrations for the four lake sites and seven stream sites of the Sherbrooke Lake Monitoring Program for
the 2018 and 2019 field seasons.
Site Type Site Mean DO (mg/L)
2019 Mean DO (mg/L)
2018 2019
Lake Lake 1 8.91 9.50
Lake 2 8.87 9.37
Lake 3 8.94 9.50
Lake 4 9.50 9.30
Sherbrooke River 8.86 10.09
Forties River 8.85 10.15
Stream Pine Lake Brook 9.36 10.55
Zwicker Brook 8.47 10.04
Butler Brook 8.99 9.70
Gully River 9.0 10.66
Peter Veinot Brook 6.41 7.56
2.2.3. Depth Profiles
2.2.3.1. At-Depth Water Temperature
The water profile at lake sites 1 and 2 in August 2019 indicate that both sites have a thermal
stratification; however, Lake 1 has a more pronounced, established thermocline compared to Lake 2
(Figure 9). The difference in thermocline strengths for 2019 is comparable to those observed in 2018.
Stratification at Lake 1 starts at 7 m depth, with a thermocline layer of approximately 4 m and a
temperature change of 3.9oC. For Lake 2, stratification starts at a shallower depth – 5 m – and has a
greater thermocline thickness and temperature change, 10 m and 12.5oC, respectively. Water
temperatures fell below the 20oC threshold for aquatic life at depths below 8 m at Lake 1 and 6 m at
Lake 2. The Lake 1 and Lake 2 2019 profiles are similar to the 2018 profiles, with only a small increase in
temperature observed at the lower depths of the two sites differentiating the two years.
The presence of a thermocline at both lake sites indicates that the nutrient-rich, cold deep waters are
not mixing with the nutrient-limited, warm surface waters during the summer months; mixing and
redistribution of nutrients within the lake is therefore only occurring during spring and fall turnover,
when water temperature is uniform at all depths and no density differences prevent mixing.
12
Figure 9: Water temperature depth profiles from two lake sites sampled in August 2018 (blue) and 2019 (green). Red line
indicates the 20oC limit for survival of aquatic organisms.
2.2.3.2. At-Depth Dissolved Oxygen
In addition to the thermocline that is present in the lake sites’ depth profiles, DO is also stratified at the
two sites (Figure 10). Of the four common DO profiles in lakes (Figure 11), both sites appear to have a
negative heterograde curve. Negative heterograde curves have a distinct reduction in DO at depth – this
may be due to increased organic matter trapped within the thermocline, acting as a source of food for
microbes and increasing DO depletion from microbial decomposition. DO increases past the
decomposition depth due to the lack of food encouraging microbial decomposition. Although the
negative heterograde curve is consistent for Lake 2 with 2018, this profile is new for Lake 1, which had a
clinograde curve in 2018. The presence of microbial decomposition at depth for both sites may be linked
to the increased algal blooms observed within the lake throughout the summer; however, even with the
increased microbial decomposition, DO concentrations for both sites are higher than those recorded in
2018. The drop in DO at Lake 2 is consistent with 2018 and is linked with high oxygen consumption of
microbial activity along the sediment surface.
0
5
10
15
20
25
0 5 10 15 20 25 30Water Temperature (oC)Depth (m)
Lake 2 - Aug 2019 Lake 2 - Aug 2018
Lake 1 - Aug 2019 Lake 1 - Aug 2018
13
Figure 10: DO depth profiles from two lake sites sampled in August 2018 (blue) and 2019 (green). Red line indicates CCME’s 6.5
mg/L DO minimum-threshold for survival of aquatic organisms.
0
1
2
3
4
5
6
7
8
9
0 5 10 15 20 25 30Dissolved Oxygen (mg/L)Depth (m)
Lake 2 - Aug 2019 Lake 2 - Aug 2018
Lake 1 - Aug 2019 Lake 1 - Aug 2018
14
Figure 11: Four common water temperature and DO depth profiles, from Hutchinson, 1957.
Due to the stratification of the lake sites 1 & 2, no summer mixing occurs, resulting in a finite supply of
DO for organisms below the thermocline until fall turnover. At depths below 7 m for Lake 1, DO falls
below the CCME 6.5 mg/L guideline, while depths below 5 m at Lake 2 also have <6.5 mg/L of DO. As
microbes continue to consume the finite supply of DO in the deep lake waters, the stress of low-DO on
aquatic organisms will only increase until DO is replenished during fall turnover.
It appears at the bottom of the lake at Lake 2, waters become hypoxic (<2 mg/L) and anoxic (<1 mg/L)
and have decreased capacity to support aquatic life (USGS, 2014; Brylinsky, 2004). Similar hypoxic and
anoxic conditions were observed for both Lake 1 and Lake 2 in 2018. As oxygen is necessary for aquatic
life, anoxic conditions can be harmful and even kill organisms that pass through anoxic waters. In
addition, anoxic conditions can cause phosphorus locked in the sediment to change states and be
released into the water column, potentially over-enriching the waters with new nutrients and causing
algal blooms.
2.2.4. pH
pH is a parameter used to assess the acidity of a substance, with pH being the negative logarithmic of
the hydrogen ion concentration of the solution (Equation 1). The pH scale ranges from 0 (most acidic) to
14 (most basic), with 7 being the neutral point. In natural waters, due to the dissolution of carbon
dioxide, water pH is slightly more acidic than neutral (~6.5), with geology, organic materials, and rain
15
inputs also affecting the water’s natural pH state; due to such natural variations, the CCME has set a pH
range of 6.5-9.0 as a guideline for the protection of aquatic life (CCME, 2007).
Equation 1: 𝑘𝐻=−log([𝐻+])
Particularly in Nova Scotia, natural organic matter, acid rock drainage from specific bedrock formations,
and decades of acid precipitation have lowered the pH of waters in the province and negatively affected
fish populations. Although the CCME has set a threshold of 6.5, many aquatic organisms have adjusted
to Nova Scotia’s acidic waters, with trout species surviving in waters as low as 4.7 (NSSA, 2014).
Although organisms can survive in acidic conditions, Harvey and Lee (1982) reported fish kills associated
with exposure to highly acidic waters from hours to days, while Courtney and Clements (1998) reported
significant reductions in invertebrates after seven days of exposure to acidic conditions (pH 4.0).
pH within the lakes and rivers of the 2019 SL monitoring program varied between 4.52-7.09 (Figures 12
and 13). All lake sites’ pH measurements fell within past site-specific pH ranges; no lake site dropped
below 5.7-pH. The October Lake 4 sample measured a pH of 6.18, this is almost 3-pH units higher than
the October 2018 sample, supporting the SL 2018 Report’s hypothesis that the low October 2018 pH
measurement was an anomaly. Of the stream sites, the lowest recorded pH was 4.52 at Pine Lake Brook
– Pine Lake Brook also had the lowest pH in 2018 and was consistently one of the lowest pH sites during
the 2018 and 2019 field seasons. As with dissolved oxygen, the rainfall-dependent samples’ data - Butler
Lake Brook, Gully River, and Peter Veinot Brook – for 2018 and 2019 are not representative of the sites’
entire field seasons due to minimal sampling.
Low pH within the SL system may pose a threat to aquatic life. All seven streams and all lake sites in
2019, except the Lake 2 August measurement, have pH values below the CCME 6.5-pH threshold. Even
when using the lower 5.0-pH threshold which is considered adequate for the survival of fish and
invertebrates (Morris et al., 1989), we still observe stream measurements below the threshold.
Although most SL streams’ pH minima have increased from 2018, all stream mean pH values have
decreased (Table 3). As the length of the low-pH conditions are unknown – due to the monthly sampling
frequency of the program – it is unclear if these conditions pose short-term or long-term concerns to
aquatic life; however, it is clear that the SL tributaries are acidic and may be negatively influencing in-
stream aquatic organism survival.
16
Figure 12: pH at four monthly lake sites (Lake 1-4) during the May-October 2019 SL water quality field season. Red line indicates
the 5.0-pH minimum threshold for survival of fish and invertebrates (Morris et al., 1989).
Figure 13: pH at four bimonthly and rainfall-dependent stream sites (Sherbrooke River, Forties River, Pine Lake, and Zwicker
Brook), in addition to three rainfall-dependent stream sites (Butler Lake Brook, Gully River, and Peter Veinot Brook), during the
May-October 2019 SL water quality field season. Red line indicates the 5.0-pH minimum threshold for survival of fish and
invertebrates (Morris et al., 1989).
4
4.5
5
5.5
6
6.5
7
7.5
05-Apr-19 05-May-19 04-Jun-19 04-Jul-19 03-Aug-19 02-Sep-19 02-Oct-19 01-Nov-19pH
Lake 1 Lake 2 Lake 3 Lake 4
4
4.5
5
5.5
6
6.5
7
7.5
05-Apr-19 05-May-19 04-Jun-19 04-Jul-19 03-Aug-19 02-Sep-19 02-Oct-19pH
Sherbrooke River Forties River Pine Lake Brook Zwicker Brook
Butler Lake Brook Gully River Peter Veinot Brook
17
Table 3: Mean pH for the four lake sites and seven stream sites of the Sherbrooke Lake Monitoring Program for the 2018 and
2019 field seasons.
Site Type Site Mean pH
2019 Mean pH
2018 2019
Lake Lake 1 6.02 5.90
Lake 2 5.92 6.30
Lake 3 6.36 6.26
Lake 4 4.80 6.10
Sherbrooke River 5.96 5.39
Forties River 5.75 5.14
Stream Pine Lake Brook 5.33 5.02
Zwicker Brook 5.79 5.68
Butler Brook 5.79 5.72
Gully River 5.62 4.58
Peter Veinot Brook 5.27 5.15
2.2.5. Total Dissolved Solids
Total dissolved solids (TDS) – a measurement of dissolved materials in water – is an invaluable
parameter. TDS can be influenced by construction, deforestation, sewage effluent, urban and
agricultural run-off, industrial waste, road salts, forest fires, and rainfall/flooding events, and therefore
provides insight into potential pollution issues affecting the water. Although there is no CCME guideline
for TDS, high concentrations of TDS can affect water’s taste, colour, and clarity (NSSA, 2014), and
reductions in clarity can decrease the depth of light penetration and affect rooted vegetation. For most
of Nova Scotia’s lakes, TDS ranges from 5 to 235 mg/L (Nova Scotia Lake Inventory Program, 2017).
TDS of the six SL lake sites never exceeded 20.0 mg/L, while most streams had TDS concentrations >20
mg/L (Table 4, Figures 14 and 15). Of the four bimonthly stream sites monitored, all sites indicated an
increase in TDS during the rainfall sampling event, suggesting an increase in solids due to overland flow.
As the rainfall-dependent samples are only collected during rainfall events, it is unclear whether their
values represent normal or elevated conditions due to the rain. In addition, although the seven streams
had high TDS concentrations during the rainfall event, the influence on lake water quality appears
minimal, as lake site TDS concentrations did not exceed their normal ranges. Butler Brook had the
highest recorded TDS concentration (33 mg/L), which is consistent with its 2017 preliminary data (33.8
mg/L) and 2018 data (39 mg/L), suggesting that the brook has naturally high TDS concentrations. TDS
concentrations from SL fall along the lower end of the TDS range for Nova Scotia’s lakes.
18
Table 4: Mean and maximum TDS concentrations from lake and river sites during the 2018 and 2019 SL field seasons.
Site Type Site Mean TDS (mg/L) Maximum TDS (mg/L)
2018 2019 2018 2019
Lake
Lake 1 18.8 16.7 20.0 17
Lake 2 18.2 16.3 19.0 17
Lake 3 18.2 16.2 19.0 17
Lake 4 18.5 16.5 19.0 17
Stream
Sherbrooke River 21.3 16.3 23 19
Forties River 19.0 19.3 24 29
Pine Lake Brook 17.9 18.3 21 28
Zwicker Brook 19.0 17.3 23 24
Butler Brook - - 39 33
Gully River - - 14 20
Peter Veinot Brook - - 21 24
Figure 14: TDS at four monthly lake sites (Lake 1-4) during the May-October 2019 SL water quality field season.
0
5
10
15
20
25
30
35
05-May-19 09-Jun-19 01-Jul-19 11-Aug-19 09-Sep-19 06-Oct-19Total Dissolved Solids (mg/L)Lake 1 Lake 2 Lake 3 Lake 4
19
Figure 15: TDS at four bimonthly and rainfall-dependent stream sites (Sherbrooke River, Forties River, Pine Lake, and Zwicker
Brook), in addition to three rainfall-dependent stream sites (Butler Lake Brook, Gully River, and Peter Veinot Brook), during the
May-October 2019 SL water quality field season.
2.3. Chemical Water Parameters
2.3.1. Total Suspended Solids
Total suspended solids (TSS) is a measurement of all suspended materials in the water column. Increases
in TSS can be natural due to erosion or general disturbance of land upstream or can be unnatural
(release of substance from deforestation, mining, etc.). According to the Nova Scotia Environment Act
(1994-95), ‘No person shall release or permit the release into the environment of a substance in an
amount, concentration or level of at a rate of release that causes or may cause adverse effect, unless
authorized by an approval of the regulations’; by monitoring and obtaining an initial reference point of
TSS and other water quality parameters prior to future potential land disturbances, the SLSC can address
and mitigate any possible substance release events.
TSS concentrations ranged from <1 mg/L to 11 mg/L for SL lake and river sites (Table 5, Figures 16 and
17). Most lake sites had <1 mg/L of TSS during the field season, with one outlying measurement of 5.6
mg/L at Lake 1 on July 1st, 2019. It appears no stream is consistently higher than others feeding into SL,
with the 11 mg/L July 1st, 2019 sample at Pine Lake Brook appearing to be an anomaly. It is unclear what
caused the Pine Lake Brook and Lake 1 anomalies for July 2019.
No stream or lake sites increased outside of normal site-specific TSS ranges during the rainfall sampling
event. This is similar to what was observed during the 2018 rainfall-dependent sampling event, when six
of the seven streams observed no difference in TSS concentrations. In Nova Scotia, TSS in lakes ranges
from 0.8 to 15 mg/L (Nova Scotia Lake Inventory Program, 2017); SL TSS concentrations fall along the
lower end of this range, except for the Pine Lake Brook July 2019 anomaly.
0
5
10
15
20
25
30
35
05-May-19 01-Jul-19 09-Sep-19Total Dissolved Solids (mg/L)Sherbrooke River Forties River Pine Lake Brook Zwicker Brook
Butler Lake Brook Gully River Peter Veinot Brook
20
Table 5: Mean TSS concentrations from lake and river sites during the 2018 and 2019 SL field seasons. As Lake 3 only sampled
bacteria in 2019, no data are available for TSS for 2019.
Site Type Site Mean TSS (mg/L)
2018 2019
Lake
Lake 1 1.1 2.3
Lake 2 1.1 1.4
Lake 3 1.0 -
Lake 4 1.1 1.5
Stream
Sherbrooke River 1.6 1.9
Forties River 1.4 1.7
Pine Lake Brook 1.3 4.6
Zwicker Brook 1.6 1.1
Butler Brook 1.8 1.0
Gully River 1.0 1.0
Peter Veinot Brook 1.0 1.0
Figure 16: TSS at three monthly lake sites (Lake 1, 2, and 4) during the May-October 2019 SL water quality field season. As Lake
3 only sampled bacteria in 2019, no data are available for 2019 and therefore Lake 3 is not included.
0
1
2
3
4
5
6
7
8
9
10
11
12
05-May-19 09-Jun-19 01-Jul-19 11-Aug-19 09-Sep-19 06-Oct-19Total Suspended Solids (mg/L)Lake 1 Lake 2 Lake 4
21
Figure 17: TSS at four bimonthly and rainfall-dependent stream sites (Sherbrooke River, Forties River, Pine Lake, and Zwicker
Brook), in addition to three rainfall-dependent stream sites (Butler Lake Brook, Gully River, and Peter Veinot Brook), during the
May-October 2019 SL water quality field season.
Secchi disk depth – the depth to which a black and white disk is just barely visible within a waterbody –
can act as a proxy for TSS in lakes. In SL, Secchi disk depths were measured for sites Lake 1-4 (Table 6).
Lake 2 had the clearest water, with a maximum depth of 4.05 m. The clarity of Lake 2 has increased
since the max depth of 2.84 m in 2018. The clarity of Lake 2 has been greater than Lake 1 for both 2018
and 2019. Both Lake 3 and 4 have maximum depths down to the lake bottom. Although Secchi depth
provides an indication of light penetration into waterbodies, the measurements can be skewed due to
the depth of the site, an individual’s eyesight, and different individuals performing the measurement on
different days.
Table 6: Maximum and mean Secchi disk depths from lake sites during the 2018 and 2019 SL field seasons. No maximum Secchi
depth is available for Lake 3 and 4, as both are visible down to the lake bottom.
Site Type Site Mean Secchi (m) Maximum Secchi (m)
2018 2019 2018 2019
Lake
Lake 1 2.21 2.10 2.65 3.55
Lake 2 2.43 2.55 2.84 4.05
Lake 3 1.78 1.46 - -
Lake 4 2.38 2.60 - -
2.3.2. Total Phosphorus
Phosphorus concentrations (both organic and inorganic) are extremely important in healthy ecosystems;
phosphorus acts as a nutrient to various organisms and plants within watersheds. Due to minimal
natural sources of phosphorus and a high demand by plants, phosphorus concentrations are low in
0
1
2
3
4
5
6
7
8
9
10
11
12
05-May-19 01-Jul-19 09-Sep-19Total Suspended Solids (mg/L)Sherbrooke River Forties River Pine Lake Brook Zwicker Brook
Butler Lake Brook Gully River Peter Veinot Brook
22
aquatic environments and therefore a growth-limiting factor. As phosphorus is a key nutrient in
freshwater environments, and not considered a toxic substance, the CCME does not have set guidelines;
however, Ontario’s Ministry of Environment and Climate Change (MOECC) has set a total phosphorus
guideline of ≤0.02 mg/L for lakes, and ≤0.03 mg/L for rivers and streams (MOE, 1979). By monitoring
phosphorus, pollution sources can be identified due to ‘pockets’ of elevated phosphorus concentrations.
In addition, by monitoring phosphorus below a lake’s thermocline, we can assess how nutrients are
being used/supplied in deeper waters, and if nutrient-enrichment will be a problem once the waters mix
during fall and spring turnover.
On average, lake sites were consistently lower than streams (Figures 18 and 19, Table 7). Lake
phosphorus concentrations ranged from <0.004 mg/L to 0.017 mg/L, while streams ranged from 0.012
mg/L to 0.032 mg/L. No lake phosphorus concentrations exceeded the MOECC lake guideline of 0.02
mg/L, while only one stream site – Pine Lake Brook – exceeded the MOECC stream guideline of 0.03
mg/L. Phosphorus concentrations increased at the four bimonthly streams during the rainfall event.
Phosphorus concentrations were also elevated at the three rainfall-dependent sites, but as these sites
were not sampled more than once, it is unclear if these phosphorus concentrations are elevated or
natural. Due to the increase in phosphorus in the bimonthly streams, it is reasonable to assume that the
rainfall caused increased flushing of phosphorus into the streams. The water quality of the lake appears
to be minimally affected by the rainfall-induced increased stream inputs, as phosphorus concentrations
did not increase at any lake sites; however, effects on the lake may be delayed due to the lag between
pollutants reaching the streams, and the travel of the pollutants downstream to the lake.
Figure 18: Total phosphorus at three monthly lake sites (Lake 1, 2, and 4) during the May-October 2019 SL water quality field
season. Red line indicates the MOECC 0.02 mg/L guideline for phosphorus in lakes. As Lake 3 only sampled bacteria in 2019, no
data are available for nutrients and therefore Lake 3 is not included.
0
0.01
0.02
0.03
0.04
0.05
05-Apr-19 05-May-19 04-Jun-19 04-Jul-19 03-Aug-19 02-Sep-19 02-Oct-19 01-Nov-19Total Phosphorus (mg/L)Lake 1 Lake 2 Lake 4
23
Figure 19: Total phosphorus at four bimonthly and rainfall-dependent stream sites (Sherbrooke River, Forties River, Pine Lake,
and Zwicker Brook), in addition to three rainfall-dependent stream sites (Butler Lake Brook, Gully River, and Peter Veinot Brook),
during the May-October 2019 SL water quality field season. Red line indicates the MOECC 0.03 mg/L guideline for phosphorus in
streams.
Phosphorus concentrations during the 2019 field season are comparable to those of 2018 (Table 7).
Minimum phosphorus concentrations within the lake sites have increased from 2018 values, while the
four bimonthly stream sites remain consistent with 2018 concentrations. Two of the three rainfall-
dependent stream sites – Butler Lake Brook and Gully River – had lower phosphorus concentrations
than the 2018 rainfall event, while Peter Veinot Brook concentrations increased by 0.001 mg/L
compared to 2018.
Table 7: Range in total phosphorus concentrations between 2018 and 2019; July-September for lake and stream samples. As
Lake 3 only sampled bacteria in 2019, no data are available for total phosphorus for 2019.
Site Type Site Total Phosphorus Range
2018 2019
Lake Lake 1 0.004-0.008 0.007-0.012
Lake 2 0.004-0.009 0.006-0.009
Lake 3 0.004-0.005 -
Lake 4 0.004 0.006-0.011
Stream Sherbrooke River 0.015-0.04 0.02-0.022
Forties River 0.017-0.04 0.015-0.026
Pine Lake Brook 0.015-0.03 0.019-0.032
Zwicker Brook 0.018-0.04 0.016-0.018
Butler Lake Brook 0.03 0.017
Gully River 0.03 0.016
Peter Veinot Brook 0.02 0.021
0
0.01
0.02
0.03
0.04
0.05
05-Apr-19 05-May-19 04-Jun-19 04-Jul-19 03-Aug-19 02-Sep-19 02-Oct-19Total Phosphorus (mg/L)Sherbrooke River Forties River Pine Lake Brook Zwicker Brook
Butler Lake Brook Gully River Peter Veinot Brook
24
Elevated phosphorus concentrations below the thermocline may indicate a possible nutrient-
enrichment event during fall turnover, with a potential for eutrophication and algal blooms. In SL,
phosphorus concentrations below the thermocline (‘phosphorus at-depth’) were equal to or higher than
surface concentrations (Table 8), indicating that the deeper lake waters are nutrient enriched. As
phosphorus concentrations were higher at-depth, it appears that there is minimal assimilation of
phosphorus below the thermocline; however, as orthophosphate concentrations were below detection
limits (0.01 mg/L), the bioavailable fraction of phosphorus is minimal, reducing the risk of nutrient
enrichment from internal loading during SL’s fall turnover.
Table 8: Total phosphorus concentrations from two lake sites, obtained both at the surface and below the thermocline, taken in
August for the SL 2018 and 2019 Water Quality Monitoring Programs, in addition to orthophosphate concentrations taken
below the thermocline in 2019.
Site Surface Phosphorus (mg/L) Phosphorus At-Depth (mg/L) Orthophosphate At-Depth
(mg/L)
2018 2019 2018 2019 2018 2019
Lake 1 0.008 0.007 0.007 0.007 - <0.01
Lake 2 0.004 0.006 0.025 0.008 - <0.01
2.3.3. Total Nitrogen
Like phosphorus, nitrogen is also a limiting nutrient for plants and other organisms in freshwater
environments. No CCME guidelines exist for nitrogen; however, Dodds and Welch (2000) have
established a ≤0.9 mg/L guideline for freshwater environments, while Underwood and Josselyn (1979)
reported a guideline of ≤0.3 mg/L for oligotrophic waterbodies.
Lake nitrogen concentrations ranged from 0.215 mg/L to 0.327 mg/L, while stream nitrogen
concentrations ranged from 0.219 mg/L to 0.784 mg/L (Figures 20 and 21, Table 9). Total nitrogen, like
total phosphorus, was lower in lake sites than stream sites. In addition, the nitrogen concentrations for
all lake sites were higher in 2019 than 2018. No stream or lake site exceeded the Dodds and Welch
(2000) 0.9 mg/L threshold; however, the Lake 1 site did exceed the Underwood and Josselyn (1979) 0.3
mg/L threshold for oligotrophic waterbodies on one occasion – 0.327 mg/L on August 11th, 2019.
Nitrogen concentrations increased following the Hurricane Dorian rainfall event. Of the bimonthly
streams monitored during the sampling program, all four streams had increases in total nitrogen during
the rainfall-dependent sampling. The three rainfall-only stream sites had similar levels as 2018 – as
these are only monitored during rainfall-only events, the range of nitrogen concentrations outside these
rainfall events is unknown. Like phosphorus, no lake sites had increases in nitrogen following the rainfall
event – this may indicate minimal impact on the lake or may be due to the lag between flushing of
nutrient pollutants into the streams and eventual transportation of these waters into the lake.
Elevated nitrogen concentrations in the 2019 lake sites, in addition to increases at all seven streams
during the rainfall event, suggests that nitrogen pollution is an issue in SL. Although the oligotrophic
25
threshold was only exceeded once in 2019, the increase in nitrogen concentrations within SL from 2018
to 2019 increases the risk of eutrophication within the lake.
Figure 20: Total nitrogen at three monthly lake sites (Lake 1, 2, and 4) during the May-October 2019 SL water quality field
season. Red solid line indicates the Dodds and Welch (2000) 0.9 mg/L nitrogen threshold for freshwaters, and red dashed line
indicates the Underwood and Josselyn (1979) 0.3 mg/L nitrogen threshold for oligotrophic lakes. As Lake 3 only sampled
bacteria in 2019, no data are available for nutrients and therefore Lake 3 is not included.
Figure 21: Total nitrogen at four bimonthly and rainfall-dependent stream sites (Sherbrooke River, Forties River, Pine Lake, and
Zwicker Brook), in addition to three rainfall-dependent stream sites (Butler Lake Brook, Gully River, and Peter Veinot Brook),
during the May-October 2019 SL water quality field season. Red line indicates the Dodds and Welch (2000) 0.9 mg/L nitrogen
threshold for freshwaters.
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
05-Apr-19 05-May-19 04-Jun-19 04-Jul-19 03-Aug-19 02-Sep-19 02-Oct-19 01-Nov-19Total Nitrogen (mg/L)Lake 1 Lake 2 Lake 4
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
05-Apr-19 05-May-19 04-Jun-19 04-Jul-19 03-Aug-19 02-Sep-19 02-Oct-19Total Nitrogen (mg/L)Sherbrooke River Forties River Pine Lake Brook Zwicker Brook
Butler Lake Brook Gully River Peter Veinot Brook
26
Table 9: Range in total nitrogen concentrations between 2018 and 2019; July-September for lake and stream samples. As Lake 3
only sampled bacteria in 2019, no data are available for total nitrogen for 2019.
Site Type Site Total Nitrogen Range (mg/L)
2018 2019
Lake Lake 1 0.185-0.359 0.267-0.327
Lake 2 0.18-0.258 0.247-0.286
Lake 3 0.19-0.29 -
Lake 4 0.194 0.215-0.27
Stream Sherbrooke River 0.503-0.714 0.409-0.59
Forties River 0.534-0.751 0.443-0.784
Pine Lake Brook 0.497-0.781 0.472-0.684
Zwicker Brook 0.66-0.711 0.398-0.516
Butler Lake Brook 0.883 0.544
Gully River 0.483 0.529
Peter Veinot Brook 0.66 0.654
Unlike phosphorus, lower nitrogen concentrations below the thermocline limit the potential for a
nutrient-enrichment event during fall turnover. In SL, nitrogen concentrations were only slightly lower
at-depth than the surface concentrations (Table 10). Lake 1 at-depth nitrogen concentrations were only
0.017 mg/L below those at the surface, while Lake 2 samples were 0.003 mg/L below surface
concentrations. Surface nitrogen concentrations have increased since 2018 for both lake sites, while
Lake 1 at-depth nitrogen concentrations have increased while Lake 2 at-depth concentrations have
decreased since 2018. As nitrogen concentrations are lower at-depth, the deeper SL waters are not a
source of internal loading, thereby minimizing the potential for eutrophication and algal blooms in the
fall season.
Table 10: Total nitrogen concentrations from two lake sites, obtained both at the surface and below the thermocline, in August
for the SL 2018 and 2019 Water Quality Monitoring Programs.
Site Surface Nitrogen (mg/L) Nitrogen At-Depth (mg/L)
2018 2019 2018 2019
Lake 1 0.263 0.327 0.223 0.31
Lake 2 0.258 0.263 0.46 0.26
2.3.4. Chlorophyll a
Chlorophyll a is a parameter used as a proxy for biological activity within water and can be an indicator
for potential algal blooms if it increases to elevated levels (Stumpf, 2001). For SL, chlorophyll a never
exceeded 7 µg/L (Figures 22 and 23, Table 11). Chlorophyll a concentrations were consistently higher at
the lake sites than stream sites, which may be due to the lower velocity of the waters and therefore
greater ability for algae to grow and thrive. The lake sites, and three of the four bimonthly stream sites,
had lower mean chlorophyll concentrations than 2018 values. All three rainfall-dependent stream
samples increased from 2018, but as these are only collected annually, it is unclear whether these
increases are beyond the normal streams’ chlorophyll a range.
27
2019 chlorophyll a concentrations are inconsistent with previous findings. Although the seasonal
variations for the 2019 stream sites are consistent with 2018 values, the lake sites diverge from 2018
trends. There is a decrease in chlorophyll a concentrations throughout the first three months at the lake
sites, as was also observed in 2018; however, there is a subsequent increase come August 2019. The
August 2019 increase does not correspond to increases in nutrient availability, as both nitrogen and
phosphorus concentrations remain within expected ranges during this period. The August increase also
does not appear to be rainfall related, as only 2 mm of rain fell in the three days prior to the August
2019 sampling event. The maintained increase in chlorophyll a concentrations during the September
and October sampling events is consistent with 2018 values, as rainfall increased and resulted in the
flushing of more materials into the lake. It is unclear why chlorophyll a concentrations increased in
August, while the three earlier months – when various algal blooms were reported within the lake – fell
below 3 mg/L. The increase in chlorophyll in the fall months is not consistent with the 2018 data; further
sampling is required to understand why concentrations increased.
Figure 22: Chlorophyll a at three monthly lake sites (Lake 1, 2, and 4) during the May-October 2019 SL water quality field season.
As Lake 3 only sampled bacteria in 2019, no data are available for chlorophyll a and therefore Lake 3 is not included.
0
1
2
3
4
5
6
7
8
9
10
05-Apr-19 05-May-19 04-Jun-19 04-Jul-19 03-Aug-19 02-Sep-19 02-Oct-19 01-Nov-19Chlorophyll A (µg/L)Lake 1 Lake 2 Lake 4
28
Figure 23: Chlorophyll a at four bimonthly and rainfall-dependent stream sites (Sherbrooke River, Forties River, Pine Lake, and
Zwicker Brook), in addition to three rainfall-dependent stream sites (Butler Lake Brook, Gully River, and Peter Veinot Brook),
during the May-October 2019 SL water quality field season.
Table 11: Maximum and mean chlorophyll a from lake and river sites during the 2018 and 2019 SL field seasons. As Lake 3 only
sampled bacteria in 2019, no data are available for chlorophyll a for 2019.
Site Type Site Mean Chlorophyll a (µg/L) Maximum Chlorophyll a (µg/L)
2018 2019 2018 2019
Lake
Lake 1 3.73 2.70 2.65 3.55
Lake 2 2.79 2.54 2.84 4.05
Lake 3 2.11 - 2.3 -
Lake 4 2.10 1.93 2.63 3.85
Stream
Sherbrooke River 1.72 0.99 3.88 1.21
Forties River 1.71 0.83 2.97 1.47
Pine Lake Brook 0.76 1.38 0.94 3.10
Zwicker Brook 5.18 1.19 17.41 1.85
Butler Brook 0.89 1.35 0.89 1.35
Gully River 0.85 1.30 0.85 1.30
Peter Veinot Brook 0.79 0.99 0.79 0.99
2.3.5. E. Coli Bacteria
Escherichia coli (E. coli) is a species of fecal coliform bacteria which are found in the waste of warm-
blooded animals and used as indicators of fecal pollution within freshwater environments. Sources of
bacteria can include agricultural lands – due to the spreading of manure on crops, stream crossings by
livestock, and livestock feces (Stephenson and Street, 1978; Hunter et al., 1999; Crane et al., 1983),
0
1
2
3
4
5
6
7
8
9
10
05-Apr-19 05-May-19 04-Jun-19 04-Jul-19 03-Aug-19 02-Sep-19 02-Oct-19Chlorophyll A (µg/L)Sherbrooke River Forties River Pine Lake Brook Zwicker Brook
Butler Lake Brook Gully River Peter Veinot Brook
29
domestic and wild animal feces, leachate from landfills (Maqbool et al., 2011), malfunctioning septic
systems, illegal straight-pipes, and stormwater run-off (both urban areas and overland flow in rural
regions).
In recreational waters, the presence of fecal pollution presents a risk to the public, as the possible
presence of pathogenic microorganisms can infect humans and animals and cause serious illnesses. As
testing for the hundreds of disease-causing microorganisms is costly and impractical, this program uses
E. coli measured in coliform forming units per 100 mL (CFU/100 mL) as an indicator of fecal pollution.
The program switched from testing fecal coliforms in 2018 to E. coli in 2019 to align with Health
Canada’s standards of using E. coli as the primary indicator bacteria of fecal contamination in
freshwaters. For recreational waters, Health Canada has set a limit of <400 CFU/100 mL of E. coli during
primary contact activities (activities where the body, face, or trunk are submersed, and it is likely that
water will be swallowed, such as: swimming, surfing, canoeing, etc.) (Health Canada, 2012). Although
the presence of E. coli indicates the presence of fecal contamination, the absence of E. coli should not
be interpreted to mean that all pathogenic organisms are absent.
In the four lake sites and seven inlet stream sites monitored during the 2019 field season, only once was
a measurement above the Health Canada primary contact limit (Figures 24 and 25). The highest E. coli
count within the lake sites was 20 CFU/100 mL, found at Lake 2 and 3 in September 2019. Samples were
below laboratory detection limits for all seven Lake 1 samples (including one replicate sample), six of
eight Lake 2 samples (including two replicate samples), four of six Lake 3 samples, and all eight Lake 4
samples (including two replicates). For the streams, concentrations ranged from <10 CFU/100 mL to 720
CFU/100 mL; the bacteria concentrations from 2019 are higher than those of 2018, which ranged from
<10 CFU/100 mL to 350 CFU/100 mL. The highest bacteria concentration was recorded at Forties River
(720 CFU/100 mL), during the rainfall-dependent event.
Elevated stream bacteria concentrations were recorded following the rainfall event of Hurricane Dorian
– these elevated concentrations may be due to flushing of bacteria on land into the streams and was
also observed in the 2018 measurements. Increases in bacteria in waterbodies following rainfall is
commonly reported in the literature (Rodgers et al., 2003; Hunter, McDonald, and Beven, 1992;
Stephenson and Street, 1978); however, it appears that the increases did not greatly affect lake water
quality. As the rainfall-dependent sampling of the seven inlet streams coincided with the September
sampling event of the four lake sites, the influence of the rainfall and streams can be observed on the
lake’s water quality. Although all streams had elevated levels of E. coli, only Lake 2 and 3 had increases
from the previous month’s E. coli levels; however, these increases were minimal, as concentrations
never exceeded 20 CFU/100 mL. Caution should still be maintained by the public after rainfall events, to
avoid exposure to high fecal bacteria concentrations, especially around streams and where streams and
the lakes intersect. In addition, caution should be taken in streams that have known bacteria sources
upstream.
30
Figure 24: E. coli at four monthly lake sites (Lake 1-4) during the May-October 2019 SL water quality field season. Red solid line
indicates Health Canada’s primary limit for recreation in freshwaters (400 CFU/100 mL), and red dashed line indicates Health
Canada’s secondary limit for recreation in freshwaters (1,000 CFU/100 mL).
Figure 25: E. coli at four bimonthly and rainfall-dependent stream sites (Sherbrooke River, Forties River, Pine Lake, and Zwicker
Brook), in addition to three rainfall-dependent stream sites (Butler Lake Brook, Gully River, and Peter Veinot Brook), during the
May-October 2019 SL water quality field season. Red solid line indicates Health Canada’s primary limit for recreation in
freshwaters (400 CFU/100 mL), and red dashed line indicates Health Canada’s secondary limit for recreation in freshwaters
(1,000 CFU/100 mL).
0
100
200
300
400
500
600
700
800
900
1000
05-May-19 09-Jun-19 01-Jul-19 11-Aug-19 09-Sep-19 06-Oct-19E. coli (CFU/100 mL)Lake 1 Lake 2 Lake 3 Lake 4
0
100
200
300
400
500
600
700
800
900
1000
05-May-19 01-Jul-19 09-Sep-19E. coli (CFU/100mL)Sherbrooke River Forties River Pine Lake Brook Zwicker Brook
Butler Lake Brook Gully River Peter Veinot Brook
31
2.4. Sediment Sampling
2.4.1. Metals
Sediments can have adverse effects on water quality in lakes and rivers, as sediment acts as a reservoir
for metals, nutrients, and organisms. During turbulence in streams, chemicals held within sediment can
be released, causing an influx of more than just TSS and TDS, but increases in metals, bacteria, organic
matter, and nutrients (Reddy et al., 1999; Brylinsky, 2004) – all of which can negatively affect a lake’s
fragile chemical equilibrium.
For sediments found at the bottom of lakes, resuspension is less likely; however, sediments can affect
bottom-feeding organisms due to high concentrations of metals which settle out of suspension and
accumulate on the lake bottom (Guthrie and Perry, 1980). Affecting bottom-feeders thereby affects
other organisms due to bioaccumulation of chemicals through the food-chain (Fishar and Ali, 2005; Chen
and Chen, 1999). In addition, different forms of phosphorus held in sediments can greatly affect lakes.
Orthophosphate is a bioavailable form of phosphorus which tends to be in lower concentrations due to
high demand by plants; however, as plants decompose, orthophosphate is released back into the
environment (CCME, 2004; Howell, 2010). For phosphorus held into complexes with metals, anoxic
conditions facilitate the dissolution of complexes and release of phosphorus from sediments (Hayes,
Reid, and Cameron, 1985). Increased levels of phosphorus released from sediments into the water
(internal phosphorus loading) can cause nutrient-enrichment and potential eutrophication and algal
blooms (Sondergaard, Jensen, and Jeppesen, 2003) – this is particularly susceptible during turnover,
when nutrient-rich bottom waters are mixed throughout the lake, providing new food sources for
organisms.
High concentrations of metals within the lake bottom sites, unlike the Zwicker Brook site, may
negatively affect aquatic life (Table 12). Within the Lake 1, 2 and 4 sites, arsenic and cadmium exceed
the CCME interim sediment quality guidelines (ISQG). Lake 1 and 2 also exceed ISQG guidelines for
mercury, with Lake 2 also exceeding manganese guidelines. In addition, selenium concentrations at Lake
2 and lead concentrations at Lake 1 appear to be close to CCME sediment guidelines and should be
monitored (CCME, 2001). The deepest parts of SL – Lake sites 1 and 2 – have the highest concentrations
of heavy metals in sediment. Water depth and slope are associated with increased metal concentrations
due to funneling of particulate matter towards deeper lake-bottom pockets, as observed by Hakanson
(1977) in Lake Vanern, Sweden.
Most SL lake sediment concentrations are comparable to metal concentrations found in four Kejimkujik
lakes monitored from 2000-2009. Sediment samples were collected by Environment and Climate Change
Canada from Hichemakaar Lake, Big Dam East, Cobrielle Lake, and Peskowesk between 2000 and 2009
(Kirk, 2018). Although the SL and Kejimkujik lakes have comparable sediment metal concentrations,
many of these metals’ concentrations exceed CCME guidelines. The high metal concentrations at Lake 1
are greater than the mean metal concentrations found at Kejimkujik for mercury and cadmium (Table
13). In addition, the concentration of cadmium in sediment at Lake 1, 2, and 4 is greater than the
maximum cadmium concentration found in the four Kejimkujik lakes. Lake 2 also exceeded the range of
manganese found within the Kejimkujik lakes, with a value 1.5 times the maximum concentration
measured within the four Kejimkujik lakes.
32
As Zwicker Brook does not exceed any guidelines, it does not appear to be a significant influence on
metal concentrations within the lake sites. It is possible that one (or multiple) of the other 13 inlet
streams is affecting metal concentrations within the lake sediments; the lake sediment metals may be
accumulating over time from metal inputs from other inlet streams. As the lake acts as a sink for all the
various metal inputs, the higher metal concentrations observed within the lake sites compared to
Zwicker Brook is reasonable, and consistent with 2018 results, where Forties River had lower metal
concentrations than the lake sites. The rotation of sediment analyses from the inlet streams will help
determine whether one or multiple streams are influencing lake sediment accumulation quantities.
33
Table 12: Concentration of metals within site sediment samples sampled on August 27th, 2018 and August 11th, 2019. Interim
sediment quality guideline (ISQG) is the recommendation by CCME of total concentrations of chemicals in surficial sediment,
while the probable effect level (PEL) is the CCME upper value in which adverse effects are expected (CCME, 2001). Nova Scotia
environmental quality standards (NSEQS) are sediment guidelines specifically set by the Nova Scotia Environment (NSE, 2014).
Light yellow indicates parameters approaching one of the guidelines, while dark yellow indicates an exceedance of one of the
guidelines.
Parameter Units
Lake
1 Lake 2 Lake
3
Lake
4
Forties
River
Zwicker
Brook RDL* Guidelines
2019 2018 2019 2018 2019 2018 2019 2018 2019 ISQG PEL NS
Aluminum (Al) mg/kg 22000 22000 25000 6700 7200 4300 4700 10 10
Antimony (Sb) mg/kg ND* ND ND ND ND ND ND 2 2
Arsenic (As) mg/kg 8.4 16 12 8.3 8.1 2.7 ND 2 2 5.9 17 17
Barium (Ba) mg/kg 49 42 50 26 17 26 18 5 5
Beryllium (Be) mg/kg ND ND 2.1 ND ND ND ND 2 2
Bismuth (Bi) mg/kg ND ND ND ND ND ND ND 2 2
Boron (B) mg/kg ND ND ND ND ND ND ND 50 50
Cadmium (Cd) mg/kg 0.76 1 0.99 1.5 0.76 ND ND 0.3 0.30 0.6 3.5 3.5
Chromium (Cr) mg/kg 15 14 14 4.6 5.1 4.7 4.0 2 2 37.3 90 90
Cobalt (Co) mg/kg 9.0 8.8 11 6.8 4.1 2.3 2.2 1 1
Copper (Cu) mg/kg 12 15 10 13 3.1 ND 4.2 2 2 35.7 197 197
Iron (Fe) mg/kg 14000 14000 15000 10000 9400 8300 6800 50 50 47766
Lead (Pb) mg/kg 34 49 24 13 13 3.3 3.3 0.5 0.50 35 91.3 91.3
Lithium (Li) mg/kg 17 10 9.7 11 14 20 21 2 2
Manganese
(Mn) mg/kg 540 480 1300 1000 290 200 110 2 2 1100
Mercury (Hg) mg/kg 0.27 0.27 0.20 0.16 ND ND ND 0.1 0.10 0.17 0.49 0.486
Molybdenum
(Mo) mg/kg ND ND 2.0 ND ND ND ND 2 2
Nickel (Ni) mg/kg 10 7.5 6.9 5.7 4.6 2.3 3.1 2 2 75
Phosphorus (P) mg/kg 1900 1900 2200 400 490 180 190 100 100
Rubidium (Rb) mg/kg 11 6.3 6.2 4.7 5.5 17 7.8 2 2
Selenium (Se) mg/kg 1.3 1.8 1.8 ND ND ND ND 1 1 2
Silver (Ag) mg/kg ND ND ND ND ND ND ND 0.5 0.50 1
Strontium (Sr) mg/kg 13 13 13 ND ND ND ND 5 5
Thallium (Tl) mg/kg 0.26 0.26 0.24 0.34 0.11 0.12 ND 0.1 0.10
Tin (Sn) mg/kg 2.5 3 1.5 2 ND ND ND 2 1
Uranium (U) mg/kg 4.3 5.7 6.5 1.7 2.0 0.52 0.77 0.1 0.10
Vanadium (V) mg/kg 23 30 34 11 12 11 9.0 2 2
Zinc (Zn) mg/kg 87 93 89 96 66 20 34 5 5 123 315 315
Orthophosphate
(P) mg/kg 0.15 0.067 0.086 0.26 0.24 0.33 0.38 0.05 0.050
*RDL = Reportable Detection Limit; ND = Not Detected
34
Table 13: Comparison of 2018 and 2019 sediment metal concentrations from SL lake and river sites to the range and mean
metal concentrations from four Kejimkujik Lakes (Hilchemakaar, Big Dam East, Cobrielle, and Peskowesk) monitored from 2000-
2009 (Kirk, 2018).
Metal Unit Lake
1
Lake 2 Lake
3
Lake
4
Forties
River
Zwicker
Brook
Kejimkujik
Range
Kejimkujik
Mean
Concentration
2019 2018 2019 2018 2019 2018 2019
Acid Extractable
Arsenic (As) mg/kg 8.4 16 12 8.3 8.1 2.7 ND* 3.55-27.1 10.50
Acid Extractable
Cadmium (Cd)
mg/kg 0.76 1.0 0.99 1.5 0.76 ND ND 0.1-0.4 0.26
Acid Extractable
Lead (Pb) mg/kg 34 49 24 13 13 3.3 3.3 43-62.5 48.40
Acid Extractable
Manganese (Mn) mg/kg 540 480 1300 1000 290 200 110 28.7-666 273.40
Acid Extractable
Mercury (Hg) mg/kg 0.27 0.27 0.20 0.16 ND ND ND 0.14-0.345 0.22
Acid Extractable
Selenium (Se) mg/kg 1.3 1.8 1.8 ND ND ND ND 1.39-3.17 2.24
*RDL = Reportable Detection Limit; ND = Not Detected
2.4.2. Hydrocarbons
Hydrocarbons are chains of carbon and hydrogen molecules which are the main components of natural
gases and petroleum products. Monitoring hydrocarbons provides insight to whether anthropogenic
activities are influencing water quality in the region - such as boating and combustion of petroleum
products causing atmospheric deposition of polycyclic aromatic hydrocarbons (PAHs) (Das, Routh, and
Roychoudhury, 2008; Andren and Strand, 1979).
Hydrocarbon testing was done for sediments rather than water samples for the 2019 field season, as
hydrocarbons are known to settle out of the water column and onto the substrate. Of the hydrocarbon
chains tested, the low molecular weight (LMW) chains were undetectable; however, the detection limits
for these chains were higher than the guidelines set by the CCME for specific LMW chains, therefore, it
is unclear whether concentrations pose a risk to the environment. Most high molecular weight (HMW)
chains were also non-detectable, but also had detection limits above select CCME HMW guidelines. For
the HMW chains between C21 and C32, the lab detected concentrations of 180,000 µg/kg for Lake 2,
87,000 µg/kg for Lake 4, and 28,000 µg/kg for Zwicker Brook. These values fall above the 6.22 µg/kg
ISQG and 135 µg/kg PEL for dibenz(a,h)anthracene; however, it is unlikely that dibenz(a,h)anthracene is
the only chain detectable between the C21-C32 chains tested, as many natural sources have long carbon
chain structures, therefore risks associated with high levels of dibenz(a,h)anthracene are unknown, but
should be considered minimal. Due to the lack of a sample available to perform hydrocarbon testing, no
data are available for hydrocarbons in the sediment at Lake 1.
Hydrocarbons should continue to be monitored at all lake sites to monitor for changes in detectable
amounts of hydrocarbons – especially at Lake 1 and Lake 4. Monitoring Lake 1 would provide
information regarding the accumulation of hydrocarbons where no data are available, while Lake 4 is
35
located near the proposed public boat launch, which would see an increase in boat traffic, and by
association, increases in the potential for hydrocarbon releases into the lake.
2.4.3. Nutrients
Regarding the phosphorus levels within the lake and river sediment (Table 14), although Lake 2 has the
highest amount of phosphorus in sediment, Zwicker Brook has the highest orthophosphate to
phosphorus ratio (0.2% orthophosphate). The higher levels of this bio-accessible phosphorus in the
stream is similar to what was observed in 2018, where Forties River also had the highest
orthophosphate to phosphorus ratio (0.18% orthophosphate). All four 2019 sites had low
orthophosphate to phosphorus ratios (≤0.2% each), indicating that the bioavailable orthophosphate is
being quickly assimilated by organisms and therefore most of the phosphorus in the sediment is in non-
bioavailable forms.
Phosphorus concentrations within SL suggest pollution within the lake. Although there is no sediment
phosphorus guideline set by the CCME, Ontario’s Provincial Sediment Quality Guidelines have a 600-
2000 mg/kg range, where 2000 mg/kg of phosphorus in sediment is the ‘severe effect level’ (Ontario
MOE, 2008). Lake 4 and Zwicker Brook are below the Ontario guidelines, suggesting minimal influence
by pollution and no negative effects on aquatic organisms; however, Lake 1 is close to the threshold,
while Lake 2 exceeds the 2000 mg/kg severe effect level, and therefore indicates pollution within the
lake. For Lake 2, the indication of pollution is greater, as both the concentrations of total phosphorus
and orthophosphate have increased from 2018 levels. The elevated phosphorus concentrations within
the Lake 1 and 2 sites indicate a potential for internal loading for phosphorus in the lake causing algal
blooms. Lake sites 1 and 2 should be considered ‘sites of concern’ and be continued to be monitored
due to high potential for nutrient-enrichment, eutrophication, and algal blooms.
Table 14: Phosphorus concentrations in sediment samples from lake and river sites sampled on August 27th, 2018, and August
11th, 2019.
Lake 1 Lake 2 Lake 3 Lake 4 Forties
River
Zwicker
Brook
Parameter (Units) 2019 2018 2019 2018 2019 2018 2019
Orthophosphate in sediment
(mg/kg)
0.15 0.0067 0.086 0.26 0.24 0.33 0.38
Acid extractable phosphorus in
sediment (mg/kg)
1900 1900 2200 400 490 180 190
3. Discussion
3.1. Trophic State of Sherbrooke Lake
Trophic states describe the productivity of a waterbody which can aid in tracking how a waterbody
changes over time. Trophic states range from oligotrophic (low productivity and minimal biomass) to
hypereutrophic (high productivity and maximum biomass). The trophic state index (TSI), proposed by
Carlson (1977), uses the depth of transparency (Secchi disk), and concentrations of chlorophyll a and
36
phosphorus to apply a number to the waterbody’s state (Equations 2, 3, and 4) – associated with its
trophic state. Tracking a waterbody’s TSI allows comparison between years using the same methods.
Equation 2: 𝑆𝑆𝐻(𝑆𝑐𝑐𝑐𝑖ℎ𝑐�ℎ𝑟𝑘)=60 −14.41 × ln(𝑀𝑐𝑎𝑘𝑆𝑐𝑐𝑐𝑖ℎ𝑐�ℎ𝑟𝑘[𝑘])
Equation 3: 𝑆𝑆𝐻(𝑐�𝑘𝑘𝑟𝑘𝑘�𝑦𝑘𝑘𝐴)=30.6 +9.81 × ln(𝑀𝑐𝑎𝑘𝑐�𝑘𝑘𝑟𝑘𝑘�𝑦𝑘𝑘𝐴[𝜇𝑔
𝐿])
Equation 4: 𝑆𝑆𝐻(𝑟𝑘𝑟𝑎𝑘𝑘�𝑘𝑟𝑘�𝑘𝑟𝑟𝑟)=4.15 +14.42 × ln(𝑀𝑐𝑎𝑘𝑟𝑘𝑟𝑎𝑘𝑘�𝑘𝑟𝑘�𝑘𝑟𝑟𝑟[𝜇𝑔
𝐿])
In SL, the lake’s TSI could be based on sites Lake 1, Lake 2, and Lake 4, therefore a TSI was created for all
three sites (Table 15; Figure 26). All sites have oligotrophic levels of phosphorus, indicating low
productivity. The phosphorus TSI scores have increased from 2018. For chlorophyll a, Lake 1 has
mesotrophic levels, while Lake 2 and 4 indicate oligotrophic levels of chlorophyll a. All three sites have
mesotrophic levels of transparency (calculated using Secchi disk depths). Concern should be minimal for
the Secchi disk/water transparency indices, as water transparency is not an exact indication of a
waterbody’s productivity, and can be influenced by factors other than biomass, such as suspended
particles within the water column (NSSA, 2014; EPA, 2002). In general, SL can be labelled primarily
oligotrophic; however, the increase in TSI phosphorus scores indicates the lake’s productivity may be
changing and being influenced by nutrient loading.
Table 15: Carlson (1977) 2018 and 2019 SL TSI scores and trophic states for total phosphorus, chlorophyll A, and Secchi disk for
Lake 1 (red), Lake 2 (blue), and Lake 4 (yellow – for 2019 only).
TSI Score Trophic State Phosphorus Chlorophyll A Secchi Disk
2018 2019 2018 2019 2018 2019
< 40 Oligotrophic 33.3
28.6
39.21
34.14
35.83
39.76
37.03
40-50 Mesotrophic 42.3
40.7
40.45 48.6
47.38
49.31
46.51
46.24
> 50 Eutrophic
37
Figure 26: Carlson TSI for lakes, with TSI ranks for SL Lake 1 (red star), Lake 2 (blue star), and Lake 4 (yellow star). Transparency
determined using Secchi disk depth. From Carlson (1977).
3.2. Algal Blooms
An algal bloom is the rapid increase and accumulation of microscopic plankton algae (phytoplankton) in
waterbodies and can be detrimental to ecosystems (Hallegraeff, 2003). Ecosystems have a fragile
balance, where biomass is sustained and limited by available nutrients; however, when excess nutrients
enter an ecosystem, biomass can expand (Heisler et al., 2008). In waterbodies, excess nutrients allow
algae to flourish, exceeding normal densities and assimilating all nutrients. The increased biomass
presence causes decreased water transparency – blocking off the depth of which sunlight penetrates a
waterbody – and as the algae decay, increased microbial decomposition reduces dissolved oxygen –
leading to hypoxic and anoxic conditions (Paerl et al., 2001).
In addition to the detrimental environmental effects, algae blooms can pose a risk to humans and
animals if they consist of cyanobacteria. Cyanobacteria, commonly referred to as blue-green algae, can
emit toxins into the water, causing serious illness and even death in humans (Lawton and Codd, 1991).
Aside from humans, cyanobacteria blooms have also been associated with fish kills (Rodger et al., 1994),
and the death of dogs (Backer et al., 2013). Although not all cyanobacteria are toxic, it is important to
test each bloom to confirm which strains are present and if toxins are a threat within the waterbody.
In 2019, SL experienced several algae blooms (Figure 27). These blooms were reported throughout the
lake, with no one singular source or location, indicating that algae growth appears to be a lake-wide
issue. From the sighting reports, blooms occurring along the north-eastern side of the lake disappated
overnight, with blooms then occuring the following day along the south-western side of the lake,
suggesting that wind and wave action may be partially responsible for the movement of blooms within
SL. The influence of wind and waves on bloom dispersion allows for greater distribution of blooms
throughout the lake, thereby affecting a greater portion of residents of SL.
38
Figure 27: Reported algae bloom locations (green triangles) within Sherbrooke Lake during the 2019 field season.
Of the reported blooms, two were sampled and sent to Maxxam Analytics to be tested for microcystins
– the toxin associated with cyanobacteria. For recreational use, total microcystins should be less than 20
µg/L (Health Canada, 2012); the two SL samples had levels below instrument detection limits, indicating
that the water was safe for recreation. In addition to the microcystin samples, an algae sample was also
sent to Dalhousie to identify the algae species present in the water. The predominant form of algae was
green algae – a non-toxic species. The increase in this species compared to previous years may be linked
to the higher concentrations of nutrients (nitrogen and phosphorus) measured within the lake in 2019
compared to 2018.
39
Bloom sightings have increased from 2018 when no bloom was reported, to nine sightings reported to
Coastal Action within the months of June and July 2019. The increase in blooms in SL is not a localized
phenomenon, as studies have observed an increase in both size and frequency of algae blooms globally,
with potential for further increases in the future (Ho et al., 2019; Michalak et al., 2013). Although the
increases in algal blooms have been linked to climate change and increasing temperatures (Ho et al.,
2019), land-use practices, such as the removal of natural filters – wetlands, vegetative buffers – and the
increased application of nutrient-rich fertilizers, have also been discussed as catalysts increasing bloom
occurrences (Huisman et al., 2018). Increased bloom sightings at SL may also be attributed to a greater
awareness of lake water quality and monitoring activities through the efforts of the SLSC. Although the
source of the blooms in SL is unclear, management of nutrients into SL is necessary, as its oligotrophic
state is easily influenced by excess nutrient loading, as observed with the increase in the lake’s
phosphorus TSI values, which can lead to an increase in the presence of algae blooms – and the
potential for toxic cyanobacteria blooms – in the lake.
3.3. Pollution
Nutrients and bacteria are two pollutants common in SL and its tributaries. Although both pollutants are
present in the natural environment, their concentrations increase with human activities. The increased
presence of nutrients poses a threat to both human and aquatic life, as nutrients can increase the lake’s
productivity, shifting its trophic status from oligotrophic to eutrophic, which increases the risk of the
formation of algal blooms. The increased presence of bacteria poses a risk for human health, as
recreation within waters with high counts of bacteria increases the risk of exposure to harmful bacteria,
viruses, and protozoa. Human activities can influence the levels of these pollutants via pollution inputs –
straight pipes, malfunctioning septic systems, lawn and crop fertilization, etc. – and the removal of
pollutant control measures – riparian zones in particular. Addressing the high levels of the nutrients and
bacteria within SL and its tributaries requires action regarding both human activity types.
As observed in 2018, rainfall events appear to be detrimental to the water quality of the SL tributaries.
The rain flushes pollutants from land-based sources towards nearby waterbodies. Spikes in both
nutrients and bacteria were observed following Hurricane Dorian at the seven inlet streams; however,
lake water quality was minimally affected. A settling time of 24 hours is advised prior to recreation
within the SL waters following a rainstorm event.
Heavy metals also appear to be pollutants within the lake, due to contaminated levels of metals found
within the lake sediment. Although heavy metals do have natural sources, and the metal concentrations
from SL sediment are comparable to nearby sediment in Kejimkujik, concentrations for mercury, arsenic,
cadmium, and manganese exceed CCME guidelines for aquatic life. The accumulation of heavy metals in
SL sediment may be exacerbated by development and atmospheric inputs originating from industry.
Although SL is considered an oligotrophic lake, its status is fragile. The lake is being influenced by
sources of nutrients and bacteria, while also experiencing long-term sediment contamination. Continued
pollutant inputs into the lake will affect the lake’s water quality, and it is important to continue
monitoring and highlighting these changes to develop management plans for the lake and encourage
the application of best management practices.
40
4. Recommendations
The following recommendations are suggested for the SL Water Quality Monitoring Program, based on
the 2019 water quality results:
● The SL Water Quality Monitoring Program should continue in 2020 and beyond, as construction
of the public access site - and increased lake usage - is expected to continue into future years,
and this program was developed to establish a water quality baseline to aid in evidence-based
decisions concerning the development of the property acquired by MODL for public use.
● Sampling of the seven inlet streams should continue during rainfall-dependent events, to
determine how rainfall events are affecting inlet streams. Overlapping monthly lake sampling
with the rainfall-dependent event is also advised, to assess how rainfall-induced changes in
stream water chemistry affect the lake.
● The stream sediment sample should continue to be rotated and sampled from a different inlet
stream each year, to gather more spatial information about nutrient and metal loading from the
different streams discharging into the lake. This will help determine if any inlet streams are
contributing excess pollutants and having an influence on lake sediment.
● In conjunction with the Sherbrooke Lake Communications Plan, both municipalities should
continue to create and distribute educational pieces to inform the public about water quality
protection and stewardship.
● There is a need for more consistency between MODL and MOC’s websites in regard to the SL
Water Quality Monitoring Program and how the information is provided. A link to each other’s
websites would be beneficial as well.
● There is a need for continued communication between the Sherbrooke Lake Stewardship
Committee and the Sherbrooke Lake Park Advisory Committee. It is recommended that these
two groups keep each other apprised of their activities and meet on a somewhat regular basis
once development of the public access site begins.
● Residents of SL should continue to be supplied with lab-certified bottles and sampling
procedures for the collection of water samples during an algae bloom.
o There should be a greater emphasis on algal bloom education, focused on increasing
awareness of what blooms are, how they occur, what they look like, and how to report
them. Information should be shared with lake residents and at the public access site for
visitors of the lake.
o A procedure should be created and shared by both municipalities to inform citizens of
the proper steps to take when they observe a potential algae bloom. Potential blooms
should be reported to Nova Scotia Environment, as the authority responsible for
assessing the bloom’s presence and risk to the public. Bloom sightings should also be
reported to the SLSC – for the purpose of tracking and analyzing bloom occurrences for
the water quality monitoring program.
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