HomeMy Public PortalAbout2022_Report_Sherbrooke Lake_Water Quality Monitoring
Sherbrooke Lake 2022 Water Quality Monitoring
Report
Kaylee MacLeod
Blake McNeely
February 2023
Prepared for:
Municipality of the District of Lunenburg
Municipality of Chester
Sherbrooke Lake Stewardship Committee
i
Sherbrooke Lake 2022 Water Quality Monitoring Report
Contributing Authors:
Kaylee MacLeod, MSc, Watersheds & Water Quality Project Coordinator, Coastal Action
Blake McNeely, BA, Watersheds & Water Quality Team Lead, Coastal Action
February 2023
Coastal Action
45 School Street, Suite 403
Mahone Bay, N.S., B0J 2E0
Ph: (902) 634-9977
Email: info@coastalaction.org
Correct citation for this publication:
MacLeod, K. & McNeely, B. (2023). Sherbrooke Lake 2022 Water Quality Monitoring Report.
Mahone Bay, Nova Scotia.
This work was supported by:
ii
Table of Contents
List of Figures ........................................................................................................................................................ iv
List of Tables ......................................................................................................................................................... vii
1.0 Introduction ..................................................................................................................................................... 1
1.1 Monitoring Program Background ....................................................................................................... 2
1.2 Review of the 2021 Sherbrooke Lake Water Quality Monitoring Report ........................... 2
2.0 2022 Water Quality Monitoring Results ............................................................................................... 3
2.1 Physical Water Quality Parameters ................................................................................................... 3
2.1.1. Chlorophyll-α, and Phycocyanin ................................................................................................. 3
2.1.2. Surface Water Temperatures....................................................................................................... 5
2.1.3 Surface Dissolved Oxygen .............................................................................................................. 7
2.1.4 pH ............................................................................................................................................................ 9
2.1.5 Total Dissolved Solids ................................................................................................................... 11
2.2 Chemical Water Quality Parameters ............................................................................................... 13
2.2.1 Total Suspended Solids ................................................................................................................ 13
2.2.2 Total Phosphorus ........................................................................................................................... 15
2.2.3 Total Nitrogen .................................................................................................................................. 18
2.3 Biological Water Quality Parameters ............................................................................................. 20
2.3.1 Fecal Bacteria ................................................................................................................................... 20
2.3.2 Microcystin-LR & Algal Blooms ................................................................................................ 21
2.4 Sediment Sampling ................................................................................................................................ 22
iii
2.4.1 Metals .................................................................................................................................................. 22
2.4.2 Sediment Phosphorus and Orthophosphate ........................................................................ 27
3.0 Discussion ...................................................................................................................................................... 28
3.1 Algae Blooms in Sherbrooke Lake ................................................................................................... 28
3.2 Trophic State of Sherbrooke Lake ................................................................................................... 29
4.0 Recommendations ...................................................................................................................................... 32
5.0 Acknowledgements .................................................................................................................................... 33
6.0 References ..................................................................................................................................................... 34
iv
List of Figures
Figure 1. Sherbrooke Lake Water Quality Monitoring Program 2022 monitoring sites........... 1
Figure 2. Phycocyanin (cells/mL) levels from the 2022 monthly sampling events at the lake
sites. The WHO provides two guidelines; Alert level 1 at 20,000 cells/mL, and Alert level 2 at
100,000 cells/mL. ................................................................................................................................................. 4
Figure 3. Phycocyanin (cells/mL) levels from the 2022 sampling events at the stream sites.
The WHO provides two guidelines; Alert level 1 at 20,000 cells/mL, and Alert level 2 at
100,000 cells/mL. ................................................................................................................................................. 4
Figure 4. Phycocyanin (cells/mL) levels from the 2022 rainfall dependent sampling event at
the stream sites, including the additional, rainfall-specific sites. The WHO provides two
guidelines; Alert level 1 at 20,000 cells/mL, and Alert level 2 at 100,000 cells/mL. Rainfall
dependent samples were taken December 1, 2022. ................................................................................ 5
Figure 5. Temperature (°C) readings from the 2022 monthly sampling events at the lake
sites. The red line indicates the 20°C threshold for cold-water fish set by NSSA. In August
Lake 2 was 24.1⁰C and Lake 4 was 24.2⁰C; in September Lake 2 was 18.5⁰C and Lake 4 was
18.3⁰C. ....................................................................................................................................................................... 6
Figure 6. Temperature (°C) readings from the 2022 sampling events at the stream sites. The
red line indicates the 20°C threshold for cold-water fish set by NSSA. ........................................... 6
Figure 7. Temperature (°C) readings from the 2022 rainfall dependent sampling at the
stream sites, including the additional, rainfall-specific sites. .............................................................. 7
Figure 8. Dissolved Oxygen (mg/L) readings from the 2022 monthly sampling events at the
lake sites. .................................................................................................................................................................. 8
Figure 9. Dissolved Oxygen (mg/L) readings from the 2022 sampling events at the stream
sites. ............................................................................................................................................................................ 8
Figure 10. Dissolved Oxygen (mg/L) readings from the 2022 rainfall dependent sampling
event at the stream sites, including the additional, rainfall-specific sites. ..................................... 9
Figure 11. pH readings from the 2022 monthly sampling events at the lake sites. The solid
red line indicates the 6.5 pH threshold set by CCME, and the dotted red line indicates the 5.0
pH threshold identified by NSSA. ................................................................................................................. 10
v
Figure 12. pH readings from the 2022 sampling events at the stream sites. The solid red line
indicates the 6.5 threshold set by CCME, and the dotted red line indicates the 5 threshold
identified by NSSA. ............................................................................................................................................ 10
Figure 13. pH readings from the 2021 rainfall dependent sampling event at the stream sites,
including the additional, rainfall-specific sites. ...................................................................................... 11
Figure 14. Total Dissolved Solids (mg/L) readings from the 2022 monthly sampling events
at the lake sites.................................................................................................................................................... 12
Figure 15. Total Dissolved Solids (mg/L) readings from the 2022 sampling events at the
stream sites. ......................................................................................................................................................... 12
Figure 16.Total Dissolved Solids (mg/L) readings from the 2022 rainfall dependent sampling
event at the stream sites, including the additional, rainfall-specific sites. .................................. 13
Figure 17. Total Suspended Solids (mg/L) readings from the 2022 monthly sampling events
at the lake sites. Lake 1, Lake 2 and Lake 4 had readings of 1.2 mg/L in August. Values of 0
are not detected. ................................................................................................................................................. 14
Figure 18. Total Suspended Solids (mg/L) readings from the 2022 sampling events at the
stream sites. Values of 0 are not detected. ............................................................................................... 14
Figure 19. Total Suspended Solids (mg/L) readings from the 2021 rainfall dependent
sampling event at the stream sites, including the additional, rainfall-specific sites. TSS was
not detected at Forties River. ........................................................................................................................ 15
Figure 20. Total Phosphorus (mg/L) levels from Lake 1, 2, and 4 from 2018, 2019, 2021, and
2022. ....................................................................................................................................................................... 16
Figure 21. Total Phosphorus (mg/L) readings from the 2022 sampling events at the stream
sites. ......................................................................................................................................................................... 17
Figure 22. Total Phosphorus (mg/L) readings from the 2022 rainfall dependent sampling
event at the stream sites, including the additional, rainfall-specific sites. .................................. 17
Figure 23. Total Nitrogen (mg/L) levels from Lake 1, 2, and 3 from 2018, 2019, and 2021.
................................................................................................................................................................................... 18
Figure 24. Total Nitrogen (mg/L) readings from the 2022 sampling events at the stream sites.
................................................................................................................................................................................... 19
vi
Figure 25. Total Nitrogen (mg/L) readings from the 2022 rainfall dependent sampling event
at the stream sites, including the additional, rainfall-specific sites ............................................... 19
Figure 26. E. coli (CFU/100 mL) readings from the 2022 sampling events at the stream sites.
................................................................................................................................................................................... 20
Figure 27. E. coli (CFU/100 mL) readings from the 2022 rainfall-dependent sampling event
at the stream sites, including the additional, rainfall-specific sites. .............................................. 21
Figure 28. Carlson TSI for Sherbrooke Lake in 2022 using the mean Secchi disk depth
(transparency), mean chlorophyll α concentration and mean total phosphorus
concentration. (Carlson 1977) ...................................................................................................................... 30
Figure 29. Comparison of Lake site TSI scores from 2018 to 2022 using the Carlson (1977)
trophic equations for total phosphorus, chlorophyll α, and Secchi disk (2020 excluded). ... 31
vii
List of Tables
Table 1. Concentrations of metals within Lake site sediment samples. Light yellow indicates
parameters approaching one of the guidelines, orange indicates an exceedance of ISQG, and
red indicates an exceedance of either the PEL or NSEQS guidelines. ............................................ 23
Table 2. Concentrations of metals within stream site sediment samples. ................................... 25
Table 3. Summary of guideline exceedances of metals in sediment samples. Light yellow
indicates parameters approaching one of the guidelines, orange indicates an exceedance of
the ISQG, and red indicates an exceedance of either the PEL or NSEQS guidelines ................. 27
Table 4. Orthophosphate and Total Phosphorus levels from the annual sediment samples at
the Lake and Stream Sites. FR = Forties River; ZB = Zwicker Brook; SR = Sherbrooke River;
PLB = Pine Lake Brook. .................................................................................................................................... 27
Table 5. TSI values for all lake sites in 2022 for three parameters. ............................................... 30
viii
Executive Summary
This report outlines the activities and results of the 2022 Sherbrooke Lake (SL) water quality
monitoring program. This project began in response to the planned development of a
municipal public access site at Sherbrooke Lake. The program’s goal was to determine a
baseline understanding of water quality conditions within SL before 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.
In June, August and September 2022, volunteers collected water samples at three lake sites
and three stream sites. Lake 3, a site that has previously been sampled, was not included in
the 2022 sample schedule except for Escherichia coli (E. coli). On December 1, 2022, Coastal
Action staff collected samples at seven stream sites following a rainfall event (rain >25 mm).
Sediment samples were also taken at the lake and one stream site once in the season. An at-
depth sample, taken below the thermocline at lake sites, was analyzed for total phosphorus
and total nitrogen.
Factors measuring or contributing to the production of algae in freshwater, including
phycocyanin, total phosphorus and total nitrogen, did not exceed guidelines set by the World
Health Organization or Ontario’s Ministry of Environment and Climate Change guidelines,
except for Pine Lake Brook, which exceeded the threshold of 0.03 mg/L for total phosphorus
in rivers and streams in August.
Surface water temperatures of all lake and stream sites exceeded or approached the 20oC
temperature threshold for cold-water fish species (NSSA 2014) during August.
Dissolved oxygen at all lake sites stayed above the minimum threshold of 6.5 mg/L set by the
Canadian Council of Ministers of the Environment (CCME) for cold-water species (CCME
1999). Some of the stream sites fell below this threshold in both August and September.
pH measurements for most sites fell below the 6.5-pH threshold set by the CCME (2002);
however, the acidity of SL waters is not uncommon for southwest NS lakes, which generally
have lower pH values than the 6.5 threshold. It appears that most of the time, the acidity of
the waters at SL poses minimal threat to organisms, except for some stream sites.
E. coli levels in the lake sites did not exceed or approach recreational guidelines. Sherbrooke
River approached the primary recreational guideline of E. coli (400 CFU/100 mL) in August.
In the rainfall-dependent sample, Pine Lake Brook and Zwicker Brook approached the
primary guideline, while Peter Veinot Brook exceeded it.
ix
Arsenic, cadmium, and mercury levels were elevated at all lake sites in the sediment samples.
Lead levels were low at most lake sites, except Lake 2 which exceeded Interim Sediment
Quality Guideline (ISQG). Metal concentrations in the stream site did not approach any of the
guidelines.
The water quality of Sherbrooke Lake and its tributaries did not identify any significant
water quality issues in 2022.
Based on the mean depth of transparency (Secchi disk), and mean concentrations of
chlorophyll-α and phosphorus, a Trophic State Index (TSI) score has been calculated
annually to assess biological productivity. Trophic states range from oligotrophic (low
productivity and minimal biomass) to hypereutrophic (high productivity and maximum
biomass). The trophic state of SL in 2018 and 2019 was oligotrophic-mesotrophic. The
transition from oligotrophic to mesotrophic is a TSI score of 40. In 2018 and 2019, the TSI
was less than a 10th of a decimal over 40, therefore classifying the lake as mesotrophic. In
2021, the TSI score was 39.4, putting the lake into an oligotrophic state. The trophic state
remained oligotrophic in 2022, with a TSI score of 39.11. SL appears to be maintaining a
steady TSI score over the four years this data has been collected.
Coastal Action recommends that the project continues in 2023, following the same program
structure as 2022, with bi-monthly monitoring of lake and stream sites; sediment sampling;
sampling regular stream sites and rainfall-dependent stream sites after rainfall exceeding 25
mm; and volunteers supplied with algae sampling equipment.
1
1.0 Introduction
The following report summarizes the results of the 2022 Sherbrooke Lake Water Quality
Monitoring Program. Monitoring activities were conducted at Sherbrooke Lake (SL) by
trained volunteers with support from Coastal Action in June, August and September 2022.
This marks the fourth year of the monitoring program, which began in 2018. Monitoring
activities did not occur in 2020 due to COVID-19 restrictions.
This program receives financial support from both the Municipality of the District of
Lunenburg (MODL) and the Municipality of Chester (MOC).
Figure 1. Sherbrooke Lake Water Quality Monitoring Program 2022 monitoring sites.
2
1.1 Monitoring Program Background
Following several years of consultations regarding the development of a municipal public
access site at Sherbrooke Lake, the Sherbrooke Lake Stewardship Committee (SLSC) was
formed. The SLSC, a joint commitment between MODL and 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 before
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.
Coastal Action acts as technical support for a group of trained volunteers, who conduct the
monthly sampling, and Coastal Action collect samples at seven stream sites following rainfall
exceeding 25 mm within 24 hours. Sampling after a significant rainfall monitors the potential
effect of runoff from land (i.e., nutrients, bacteria, sediment), which may impact water
quality. Following preliminary ground-truthing activities in 2017, the full Sherbrooke Lake
Water Quality Monitoring Program was conducted in 2018, 2019, 2021 and 2022.
Further details on the program can be found in the Sherbrooke Lake Water Quality
Monitoring Program, and the Sherbrooke Lake Water Quality Monitoring Report (2018, 2019
& 2021); all are available upon request from either MOC or MODL.
1.2 Review of the 2021 Sherbrooke Lake Water Quality Monitoring Report
In 2018 and 2019, the overall trophic state of Sherbrooke Lake was oligotrophic-
mesotrophic, indicating that the biological productivity of the lake did not change during that
period. In 2021, the trophic state of the lake was oligotrophic. The overall trophic state index
(TSI) scores have remained relatively steady over the three years this data has been
collected. The monitoring program did not identify any significant issues with the water
quality of SL in 2018, 2019 and 2021.
An algal bloom was detected at the outlet to Gully Lake on July 7, 2021. Volunteers collected
and submitted a water sample to BV Labs. No Microcystin-LR was detected in the sample.
3
None of the SL sites exceeded the phosphorus guideline of 0.02 mg/L in 2021. All stream
sites remained under the 0.03 mg/L MOECC stream guidelines for phosphorus.
Sediment was sampled at Lake sites 1, 2, and 4, and at the mouth of Sherbrooke River to test
for metal concentrations. At Lake 2 and 4, arsenic exceeded the ISQG (Interim Sediment
Quality Guidelines). At Lake 4, arsenic and cadmium exceeded the ISQG. Lake 1 had no metals
exceeding ISQG; however, mercury was approaching the ISQG. Sherbrooke River displayed
low concentrations of metals with no parameter exceeding or approaching any of the
sediment guidelines.
2.0 2022 Water Quality Monitoring Results
2.1 Physical Water Quality Parameters
2.1.1. Chlorophyll-α, and Phycocyanin
In 2021, a ProDSS Total Algae PC Sensor was purchased by MODL to use on the ProDSS YSI
unit owned jointly by MOC and MODL. This probe measures concentrations of chlorophyll-α
and phycocyanin present in water. Phycocyanin is a pigment found in cyanobacteria, or blue-
green algae, and provides an estimate of total cyanobacteria production. Chlorophyll-α is a
pigment produced by all types of algae and provides an estimate of total algae production.
Collecting this data over multiple seasons will provide baseline concentrations of
phycocyanin in SL, which can vary across waterbodies. Long-term monitoring with this
probe, paired with the collection of Microcystin-LR water samples during blooms, will help
to identify spikes in phycocyanin concentrations and build a predictive curve for the
relationship between the concentrations of these algal pigments and the occurrence of algal
blooms in SL.
Algal concentrations are measured as Relative Fluorescence Units (RFU). Phycocyanin RFU
units were converted to the total number of cells (Genzoli and Kann 2016). World Health
Organization (WHO) provides two guideline levels, ‘alert level 1’ is reached when 20,000
phycocyanin cells/mL are observed, and ‘alert level 2’ is reached when 100,000 phycocyanin
cells/mL are observed. At no point were the WHO guidelines exceeded or approached
(Figure 2, Figure 3, Figure 4). The data was not collected before, during, or immediately after
any known algae blooms.
4
Figure 2. Phycocyanin (cells/mL) levels from the 2022 monthly sampling events at the lake sites. The WHO provides two
guidelines; Alert level 1 at 20,000 cells/mL, and Alert level 2 at 100,000 cells/mL.
Figure 3. Phycocyanin (cells/mL) levels from the 2022 sampling events at the stream sites. The WHO provides two guidelines;
Alert level 1 at 20,000 cells/mL, and Alert level 2 at 100,000 cells/mL.
-1000
-800
-600
-400
-200
0
200
400
June July August September
Ph
y
c
o
c
y
a
n
i
n
(
C
e
l
l
s
/
m
L
)
Lake 1 Lake 2 Lake 4
-1000
-500
0
500
1000
1500
June July August September
Ph
y
c
o
c
y
a
n
i
n
(
C
e
l
l
s
/
m
L
)
Sherbrooke River Forties River Pine Lake Brook Zwicker Brook
5
Figure 4. Phycocyanin (cells/mL) levels from the 2022 rainfall dependent sampling event at the stream sites, including the
additional, rainfall-specific sites. The WHO provides two guidelines; Alert level 1 at 20,000 cells/mL, and Alert level 2 at
100,000 cells/mL. Rainfall dependent samples were taken December 1, 2022.
2.1.2. Surface Water Temperatures
Water temperatures were recorded in June, August and September at all lake sites, except
Lake 3 which was only sampled for Escherichia coli (E. coli) in the 2022 field season. The
stream sites were sampled in June, August, and September. Temperature readings were also
taken during a rainfall dependent event in December at all stream sites, including the
additional rainfall-specific sites. Temperatures at the lake sites ranged from 18.3°C to 24.2°C
(Figure 5). The highest temperature recorded was at Lake 4 in August, but all other lake sites
had similar temperatures during this time. Lake sites 2 and 4 exceeded the 20oC temperature
threshold for cold-water fish species in June, while all lake sites exceeded this threshold in
August (Nova Scotia Salmon Association [NSSA] 2014). All sites were below the threshold in
September.
The stream sites showed cooler temperatures than the lake, ranging from 12.5°C to 22.5°C
(Figure 6). The highest temperature recorded was at Sherbrooke River in August.
Sherbrooke River exceeded the 20°C temperature threshold for cold-water fish species in
June and August. Forties River and Zwicker Brook both exceeded the threshold in August,
while Pine Lake Brook was just below at 19.9°C.
0
500
1000
1500
2000
2500
3000
3500
Ph
y
c
o
c
y
a
n
i
n
(
C
e
l
l
s
/
m
L
)
Stream Site
6
Figure 5. Temperature (°C) readings from the 2022 monthly sampling events at the lake sites. The red line indicates the 20°C
threshold for cold-water fish set by NSSA. In August Lake 2 was 24.1⁰C and Lake 4 was 24.2⁰C; in September Lake 2 was
18.5⁰C and Lake 4 was 18.3⁰C.
Figure 6. Temperature (°C) readings from the 2022 sampling events at the stream sites. The red line indicates the 20°C
threshold for cold-water fish set by NSSA.
Surface water temperature readings were taken during the rainfall dependent sampling on
December 1, 2022, at each of the stream sites, including three additional sites not included
in the regular monthly samples. These samples were taken later than usual in the year due
to a lack of significant rainfall during the summer and fall months which led to low water
14
16
18
20
22
24
26
June July August September October
Te
m
p
e
r
a
t
u
r
e
(
⁰C
)
Lake 1 Lake 2 Lake 4
8
10
12
14
16
18
20
22
24
June July August September
Te
m
p
e
r
a
t
u
r
e
(
°C)
Sherbrooke River Forties River Pine Lake Brook Zwicker Brook
7
flow following rainfall events and staff safety for sampling following significant rainfall from
Hurricane Fiona. Temperatures from the rainfall sampling range from 5°C to 7.3°C (Figure
7).
Figure 7. Temperature (°C) readings from the 2022 rainfall dependent sampling at the stream sites, including the additional,
rainfall-specific sites.
2.1.3 Surface Dissolved Oxygen
Dissolved oxygen (DO) was recorded in June, August and September at all lake and stream
sites, except Lake 3 which was not sampled. DO readings were also taken during the rainfall
dependent sampling in December at all stream sites, including the additional rainfall-specific
sites. DO readings at the lake sites ranged from 8.18 mg/L to 9.94 mg/L (Figure 8). The
lowest reading was taken at Lake 4 in August. DO is a requirement for the survival of aquatic
organisms, with a minimum threshold of 6.5 mg/L set by the Canadian Council of Ministers
of the Environment (CCME) for cold-water species (CCME 1999). No readings below this
threshold were recorded at any regularly monitored lake site in 2022.
DO readings at the stream sites ranged from 3.42 mg/L to 10.10 mg/L (Figure 9). Forties
River and Pine Lake Brook were below the 6.5 mg/L threshold in both August and
September. Forties River was below the threshold in September.
0
1
2
3
4
5
6
7
8
Sherbrooke
River
Forties
River
Pine Lake
Brook
Zwicker
Brook
Butler Lake
Brook
Gully River Peter
Veinot
Brook
Te
m
p
e
r
a
t
u
r
e
(
°C)
Stream Site
8
Figure 8. Dissolved Oxygen (mg/L) readings from the 2022 monthly sampling events at the lake sites.
Figure 9. Dissolved Oxygen (mg/L) readings from the 2022 sampling events at the stream sites.
Dissolved oxygen readings were taken during the rainfall dependent sampling event on
December 1, 2022, at each of the stream sites, including three additional sites not included
in the regular monthly samples. DO levels ranged from 10.55 mg/L to 12.56 mg/L (Figure
10). None of the readings were below the 6.5 mg/L threshold.
7
8
9
10
11
12
June July August September October
Di
s
s
o
l
v
e
d
O
x
y
g
e
n
(
m
g
/
L
)
Lake 1 Lake 2 Lake 4
0
2
4
6
8
10
12
June July August September
Di
s
s
o
l
v
e
d
O
x
y
g
e
n
(
m
g
/
L
)
Sherbrooke River Forties River Pine Lake Brook Zwicker Brook
9
Figure 10. Dissolved Oxygen (mg/L) readings from the 2022 rainfall dependent sampling event at the stream sites, including
the additional, rainfall-specific sites.
2.1.4 pH
pH, a measurement of the acidity of a liquid, was recorded in June, August and September at
all lake and stream sites, except Lake 3 which was not sampled. pH readings were also taken
during a rainfall dependent sampling event in December at all stream sites, including the
additional, rainfall-specific sites. Although the pH measurements for most sites fell below the
6.5-pH threshold set by the CCME (CCME 2002), the acidity of SL waters is not uncommon
for southwest NS lakes. As Nova Scotia has experienced high amounts of acid precipitation
in the past, and its geology limits the replenishment of base cations to soils (NSSA 2015),
surface waters in southwest Nova Scotia are generally lower than the 6.5-pH threshold. In
addition, though the Sherbrooke Lakes’ pH values are lower than 6.5 pH, many fish species
can survive in waters >5.0-pH (NSSA 2014) and therefore it appears that most of the time,
the acidity of the waters at SL poses minimal threat to organisms, except for some stream
sites.
9.5
10
10.5
11
11.5
12
12.5
13
Sherbrooke
River
Forties
River
Pine Lake
Brook
Zwicker
Brook
Butler Lake
Brook
Gully River Peter
Veinot
Brook
Di
s
s
o
l
v
e
d
O
x
y
g
e
n
(
m
g
/
L
)
Stream Site
10
Figure 11. pH readings from the 2022 monthly sampling events at the lake sites. The solid red line indicates the 6.5 pH
threshold set by CCME, and the dotted red line indicates the 5.0 pH threshold identified by NSSA.
Figure 12. pH readings from the 2022 sampling events at the stream sites. The solid red line indicates the 6.5 threshold set by
CCME, and the dotted red line indicates the 5 threshold identified by NSSA.
4.5
5
5.5
6
6.5
7
7.5
8
June July August September October
pH
Lake 1 Lake 2 Lake 3 Lake 4
4.5
5
5.5
6
6.5
7
June July August September
pH
Sherbrooke River Forties River Pine Lake Brook Zwicker Brook
11
Figure 13. pH readings from the 2021 rainfall dependent sampling event at the stream sites, including the additional,
rainfall-specific sites.
2.1.5 Total Dissolved Solids
Total Dissolved Solids (TDS) were recorded in June, August and September at all lake and
stream sites, except Lake 3 which was not sampled. TDS readings were also taken during a
rainfall dependent sampling event in December at all stream sites, including the additional,
rainfall-specific sites. TDS readings at the lake sites ranged from 14 mg/L to 16 mg/L (Figure
14), and 2 mg/L to 27 mg/L at the stream sites (Figure 15). The highest reading of all lake
sites was taken in August, and the highest reading of the stream sites was taken at Zwicker
Brook in August.
0
1
2
3
4
5
6
Sherbrooke
River
Forties
River
Pine Lake
Brook
Zwicker
Brook
Butler Lake
Brook
Gully River Peter
Veinot
Brook
pH
Stream Site
12
Figure 14. Total Dissolved Solids (mg/L) readings from the 2022 monthly sampling events at the lake sites.
Figure 15. Total Dissolved Solids (mg/L) readings from the 2022 sampling events at the stream sites.
Total Dissolved Solids readings were taken during a rainfall dependent sampling event on
December 1, 2022, at each of the stream sites, including three additional sites not included
in the regular monthly samples. TDS levels ranged from 19.5 mg/L to 27.3 mg/L (Figure 16).
0
5
10
15
20
June August SeptemberTo
t
a
l
D
i
s
s
o
l
v
e
d
S
o
l
i
d
s
(
m
g
/
L
)
Lake 1 Lake 2 Lake 4
0
5
10
15
20
25
30
June August Sept
To
t
a
l
D
i
s
s
o
l
v
e
d
S
o
l
i
d
s
(
m
g
/
L
)
Sherbrooke River Forties River Pine Lake Brook Zwicker Brook
13
Figure 16.Total Dissolved Solids (mg/L) readings from the 2022 rainfall dependent sampling event at the stream sites,
including the additional, rainfall-specific sites.
There is no guideline for TDS set by the CCME for the protection of aquatic health; however,
Hinch and Underwood (1985) found that pristine Nova Scotian lakes had an average of 20
mg/L. The presence of high TDS is not necessarily harmful as dissolved materials can be from
both anthropogenic and natural sources. As TDS does not have a guideline for the protection
of aquatic organisms, TDS concentrations do not appear to be detrimental to Sherbrooke
Lake.
2.2 Chemical Water Quality Parameters
2.2.1 Total Suspended Solids
Total Suspended Solids (TSS) were measured as the value of solids suspended in a water
column that do not pass through a 45 µm glass fibre filter. Samples were recorded in June,
August, and September at all lake sites, except Lake 3 which was not sampled (Figure 17).
The stream sites were also sampled in June, August, and September (Figure 18). TSS samples
were also taken during a rainfall dependent sampling event in December at all stream sites,
including the additional, rainfall-specific sites. In some cases, TSS concentrations were so
low that lab results displayed a ‘not detected’ (ND) reading. The TSS samples from the lake
sites ranged from ND to 1.2 mg/L, and from ND to 25 mg/L at the stream sites.
0
5
10
15
20
25
30
Sherbrooke
River
Forties
River
Pine Lake
Brook
Zwicker
Brook
Butler Lake
Brook
Gully River Peter
Veinot
Brook
To
t
a
l
D
i
s
s
o
l
v
e
d
S
o
l
i
d
s
(
m
g
/
L
)
Stream Site
14
Figure 17. Total Suspended Solids (mg/L) readings from the 2022 monthly sampling events at the lake sites. Lake 1, Lake 2
and Lake 4 had readings of 1.2 mg/L in August. Values of 0 are not detected.
Figure 18. Total Suspended Solids (mg/L) readings from the 2022 sampling events at the stream sites. Values of 0 are not
detected.
Total Suspended Solids samples were taken during a rainfall dependent sampling event on
December 1, 2022, at each of the stream sites, including three additional sites not included
in the regular monthly samples. TSS levels ranged from ND to 2.4 mg/L (Figure 19).
0.00
0.20
0.40
0.60
0.80
1.00
1.20
1.40
June July August September
To
t
a
l
S
u
s
p
e
n
d
e
d
S
o
l
i
d
s
(
m
g
/
L
)
Lake 1 Lake 2 Lake 4
0
5
10
15
20
25
30
June August Sept
To
t
a
l
S
u
s
p
e
n
d
e
d
S
o
l
i
d
s
(
m
g
/
L
)
Sherbrooke River Forties River Pine Lake Brook Zwicker Brook
15
Figure 19. Total Suspended Solids (mg/L) readings from the 2021 rainfall dependent sampling event at the stream sites,
including the additional, rainfall-specific sites. TSS was not detected at Forties River.
As the CCME has a guideline of a 10 mg/L allowable increase from baseline in waterbodies
with TSS ≤ 100 mg/L (CCME 2002), the levels observed in 2022 are not a threat to aquatic
organisms.
2.2.2 Total Phosphorus
Total phosphorus (TP) levels were recorded in June, August and September at all lake and
stream sites, except Lake 3 which was not sampled. TP readings were also taken during a
rainfall dependent sampling event in December at all stream sites, including the additional,
rainfall-specific sites. TP readings at the lake sites ranged from not detected (ND) to 0.008
mg/L, and 0.012 mg/L to 0.033 mg/L at the stream sites. The highest lake concentration was
observed at all lake sites in August, and the highest concentration of the stream sites was
observed at Pine Lake Brook in August. Compared to the previous years, TP levels in the Lake
sites have been less varied, and lower in 2022; however, data from May, July, September and
October are missing for 2022 (Figure 20).
Ontario’s Ministry of Environment and Climate Change (MOECC) has established two
guidelines for phosphorus in water bodies: ≤ 0.02 mg/L for lakes, and ≤ 0.03 mg/L for rivers
and streams (Ontario’s Ministry of Environment [MOE] 1979). TP concentrations in the lake
did not exceed the MOECC guidelines. Pine Lake Brook exceeded the threshold of 0.03 mg/L
in August.
0
1
2
3
4
5
6
Sherbrooke
River
Forties
River
Pine Lake
Brook
Zwicker
Brook
Butler Lake
Brook
Gully River Peter
Veinot
Brook
To
t
a
l
S
u
s
p
e
n
d
e
d
S
o
l
i
d
s
(
m
g
/
L
)
Stream Site
16
Total phosphorus samples were taken during a rainfall dependent sampling event on
December 1, 2022, at each of the stream sites, including three additional sites not included
in the regular monthly samples. TP levels ranged from 0.007 mg/L to 0.015 mg/L (Figure
22).
Figure 20. Total Phosphorus (mg/L) levels from Lake 1, 2, and 4 from 2018, 2019, 2021, and
2022.
0.000
0.005
0.010
0.015
To
t
a
l
P
h
o
s
p
h
o
r
o
u
s
(
m
g
/
L
)
Date
Lake 1
2018 2019 2021 2022
0
0.005
0.01
0.015
To
t
a
l
P
h
o
s
p
h
o
r
o
u
s
(
m
g
/
L
)
Date
Lake 2
2018 2019 2021 2022
0
0.005
0.01
0.015
To
t
a
l
P
h
o
s
p
h
o
r
o
u
s
(
m
g
/
L
)
Date
Lake 4
2018 2019 2021 2022
17
Figure 21. Total Phosphorus (mg/L) readings from the 2022 sampling events at the stream sites.
Figure 22. Total Phosphorus (mg/L) readings from the 2022 rainfall dependent sampling event at the stream sites, including
the additional, rainfall-specific sites.
In September, Total Phosphorus samples were taken below the thermocline at Lake 1 and
Lake 2. Results show 0.008 mg/L at Lake 1, and 0.006 mg/L at Lake 2. These results do not
exceed the MOECC guidelines and are similar to the surface Total Phosphorus levels.
0.010
0.015
0.020
0.025
0.030
0.035
June August September
To
t
a
l
P
h
o
s
p
h
o
r
u
s
(
m
g
/
L
)
Sherbrooke River Forties River Pine Lake Brook Zwicker Brook
0.000
0.002
0.004
0.006
0.008
0.010
0.012
0.014
0.016
Sherbrooke
River
Forties
River
Pine Lake
Brook
Zwicker
Brook
Butler Lake
Brook
Gully River Peter
Veinot
Brook
To
t
a
l
P
h
o
s
p
h
o
r
u
s
(
m
g
/
L
)
Stream Sites
18
2.2.3 Total Nitrogen
Total Nitrogen (TN) levels were recorded in June, August and September at all lake and
stream sites, except Lake 3 which was not sampled. TN readings were also taken during a
rainfall dependent sampling event in December at all stream sites, including the additional,
rainfall-specific sites. TN readings at the lake sites ranged from 0.201 mg/L to 0.238 mg/L
(Figure 23), and 0.396 mg/L to 0.781 mg/L at the stream sites (Figure 24). The highest
concentration at the lake sites occurred at Lake 2 in August, and the highest stream
concentration occurred at Pine Lake Brook in August.
Total Nitrogen samples were taken during a rainfall dependent sampling event on December
1, 2022, at each of the stream sites, including three additional sites not included in the
regular monthly samples. TN levels ranged from 0.386 mg/L to 0.510 mg/L (Figure 25).
Dodds and Welch (2000) have established a guideline for nitrogen in waterbodies of 0.9
mg/L. This guideline was not approached or exceeded by any sites.
Figure 23. Total Nitrogen (mg/L) levels from Lake 1, 2, and 3 from 2018, 2019, and 2021.
0.15
0.20
0.25
0.30
0.35
0.40
To
t
a
l
N
i
t
r
o
g
e
n
(
m
g
/
L
)
Lake 1
2018 2019 2021 2022
0.15
0.20
0.25
0.30
0.35
0.40
To
t
a
l
N
i
t
r
o
g
e
n
(
m
g
/
L
)
Lake 2
2018 2019 2021 2022
0.15
0.20
0.25
0.30
0.35
0.40
To
t
a
l
N
i
t
r
o
g
e
n
(
m
g
/
L
)
Lake 4
2018 2019 2021 2022
19
Figure 24. Total Nitrogen (mg/L) readings from the 2022 sampling events at the stream sites.
Figure 25. Total Nitrogen (mg/L) readings from the 2022 rainfall dependent sampling event at the stream sites, including the
additional, rainfall-specific sites
Total Nitrogen concentrations were measured below the thermocline at Lake 1 and Lake 2.
Results show 1.47 mg/L at Lake 1, and 0.361 mg/L at Lake 2. The results from Lake 1
exceeded the Dodds and Welch guideline of 0.9 mg/L. Higher nitrogen concentrations below
the thermocline may indicate a possible nutrient-enrichment event during fall turnover, with
a potential for eutrophication and algal blooms.
0.000
0.100
0.200
0.300
0.400
0.500
0.600
0.700
0.800
0.900
June August September
To
t
a
l
N
i
t
r
o
g
e
n
(
m
g
/
L
)
Sherbrooke River Forties River Pine Lake Brook Zwicker Brook
0.000
0.100
0.200
0.300
0.400
0.500
0.600
Sherbrooke
River
Forties
River
Pine Lake
Brook
Zwicker
Brook
Butler Lake
Brook
Gully River Peter
Veinot
Brook
To
t
a
l
N
i
t
r
o
g
e
n
(
m
g
/
L
)
Steam Sites
20
2.3 Biological Water Quality Parameters
2.3.1 Fecal Bacteria
E. coli samples were taken in June, August, and September at all lake and stream sites.
Readings were also taken during a rainfall dependent sampling event in December at all
stream sites, including the additional, rainfall-specific sites. E. coli readings at the lake sites
ranged from not detected (ND) to 2 CFU/100 mL, and not detected to 370 CFU/100 mL at
the stream sites (Figure 27). Of the 12 total E. coli samples taken at the lake sites, only four
showed any detectable concentrations. The samples collected in August at Lake 1, Lake 3,
and Lake 4, as well as Lake 4 in September, showed 2 CFU/100 mL. All other samples did not
detect any E. coli. The highest concentration was observed at Sherbrooke River in August
(Figure 26).
Figure 26. E. coli (CFU/100 mL) readings from the 2022 sampling events at the stream sites.
E. coli samples were taken during a rainfall dependent sampling event on December 1, 2022,
at each of the stream sites, including three additional sites not included in the regular
monthly samples. E. coli concentrations ranged from 30 CFU/100 mL to 550 CFU/100 mL
(Figure 27).
0
50
100
150
200
250
300
350
400
June August September
E.
c
o
l
i
(C
F
U
/
1
0
0
m
L
)
Sherbrooke River Forties River Pine Lake Brook Zwicker Brook
21
Figure 27. E. coli (CFU/100 mL) readings from the 2022 rainfall-dependent sampling event at the stream sites, including the
additional, rainfall-specific sites.
Health Canada has set primary and secondary recreational contact guidelines for E. coli in
freshwaters, ≤400 CFU/100 mL and ≤1000 CFU/100 mL, respectively (Health Canada 2012).
Sherbrooke River approached this guideline in August. Pine Lake Brook and Zwicker Brook
also approached this guideline in the rainfall dependent sample. Peter Veinot Brook
exceeded the primary guideline of 400 CFU/100 mL in the rainfall-dependent sample.
2.3.2 Microcystin-LR & Algal Blooms
The recreational guideline for cyanobacterial toxins – Microcystin-LR is 10 µg/L (Health
Canada 2012). This guideline is meant to protect against exposure to microcystins and other
toxins that may be present in an algal bloom. Microcystin-LR can persist in aquatic
environments after a visible bloom has dissipated (Jones and Orr 1994).
Not all algal blooms are toxic cyanobacteria blooms, and Microcystin-LR is only one of the
possible toxins in a cyanobacteria bloom. For this reason, every algal bloom should be
treated with caution and reported to Nova Scotia Environment (NSE).
An algal bloom was reported at the North East section of the lake along the shoreline of
Sherbrooke Forest in 2022. This bloom dissipated before volunteers could sample it.
0
100
200
300
400
500
600
Sherbrooke
River
Forties
River
Pine Lake
Brook
Zwicker
Brook
Butler Lake
Brook
Gully River Peter
Veinot
Brook
E.
c
o
l
i
CF
U
/
1
0
0
m
L
Stream Sites
22
2.4 Sediment Sampling
Sediment sampling at sites Lake 1, 2, and 4 has occurred each year since 2018. Sediment
samples are collected from one stream each year. In 2022, the bottom substrate was
analyzed for metals, phosphorus, and orthophosphate, to assess the risk of internal nutrient
loading within the lake and the potential risk from the accumulation of metals within the
sediments.
2.4.1 Metals
Three guidelines are used for sediment analysis; the CCME’s recommended Interim
Sediment Quality Guideline (ISQG), the CCME’s Probable Effect Levels (PEL), and the Nova
Scotia Environmental Quality Standards (NSEQS) contamination threshold. Sediment
samples are collected annually from the lake sites and one stream site. In 2018, Lake 2, Lake
3, and Forties River were sampled. In 2019, and 2021 Lake 1, Lake 2, and Lake 4 were
sampled. The 2019 stream was Zwicker Brook and the 2021 stream was Sherbrooke River.
Arsenic concentrations were noticeably high and exceeded the ISQG guidelines at all lake
sites every year except at Lake 1 in 2021. In 2018 and 2019, Lake 2 had the highest recorded
levels of arsenic, with 2018 levels approaching the PEL & NSEQS guidelines. Increased
arsenic levels reduce the abundance of benthic invertebrates, the main food source for many
aquatic species (CCME 2002). Of the four stream sites sampled, none have arsenic levels of
concern, and no metal concentrations show levels approaching any of the guidelines. Arsenic
levels increased from 2021 to 2022 at Lakes 1 and 2, whereas Lake 4 had a slight decrease
of 1.5 mg/kg.
Cadmium levels exceeded the ISQG guidelines at all lake sites in all years except at Lake 1
and Lake 2 in 2021. The highest cadmium concentration recorded was 1.5 mg/kg at Lake 3
in 2018. Like arsenic, cadmium reduces the abundance of benthic invertebrates and damages
aquatic species. However, cadmium levels are generally low at all sites and were not detected
at any of the stream sites. The highest concentration recorded only exceeded the ISQG
guidelines by 0.9 mg/kg.
Lead levels were low at all sites each year, with only the ISQG guideline being exceeded in
2018 and 2022 at Lake 2. At Lake 1 in 2019, the ISQG guideline was approached but not
exceeded with a level of 34 mg/kg. Lead levels at the stream sites were very low in all years.
Lead can reduce the abundance of benthic invertebrates, and depending on the
physicochemical conditions, can be harmful to other aquatic organisms (CCME 2002).
23
Mercury levels are relatively high at all lake sites. The ISQG guideline was either exceeded or
approached at each lake site each year except Lake 4 in 2019. The level of mercury increased
at each site from 2021 to 2022. Mercury was not detected at any of the stream sites.
Selenium levels approached the NSEQ guideline at Lake 2 in 2018, 2021, and 2022, and at
Lake 4 in 2021. Selenium was undetected at all stream sites.
Table 1. Concentrations of metals within Lake site sediment samples. Light yellow indicates parameters approaching one of
the guidelines, orange indicates an exceedance of ISQG, and red indicates an exceedance of either the PEL or NSEQS guidelines.
UNITS Lake 1 Lake 2
Lake
3 Lake 4
Concentration
Guidelines
Metals 2019 2021 2022 2018 2019 2021 2022 2018 2019 2021 2022 ISQG PEL NS
Acid Extractable Aluminum
(Al) mg/kg 22000 12000 18000 22000 25000 16000 18000 6700 7200 22000 20000
Acid Extractable Antimony (Sb) mg/kg ND ND <2 (ND) ND ND ND <2 (ND) ND ND ND <2 (ND) 25
Acid Extractable Arsenic (As) mg/kg 8.4 4.8 6.8 16 12 6.8 12 8.3 8.1 9.8 8.3 5.9 17 17
Acid Extractable Barium (Ba) mg/kg 49 26 42 42 50 30 35 26 17 35 33
Acid Extractable Beryllium
(Be) mg/kg ND ND 1.5 ND 2.1 ND 1.6 ND ND ND 1.5
Acid Extractable Bismuth (Bi) mg/kg ND ND <2 (ND) ND ND ND <2 (ND) ND ND ND <2 (ND)
Acid Extractable Boron (B) mg/kg ND ND <50
(ND) ND ND ND <50
(ND) ND ND ND <50
(ND)
Acid Extractable Cadmium
(Cd) mg/kg 0.76 0.31 0.69 1 0.99 0.46 0.81 1.5 0.76 0.63 0.66 0.6 3.5 3.5
Acid Extractable Chromium (Cr) mg/kg 15 8 13 14 14 8.7 11 4.6 5.1 14 12 37.3 90 90
Acid Extractable Cobalt (Co) mg/kg 9 4.3 5.7 8.8 11 5.2 5.7 6.8 4.1 6.6 6.2
Acid Extractable Copper (Cu) mg/kg 12 6 9.3 15 10 6.1 8.7 13 3.1 9.5 8.4 35.7 197 197
Acid Extractable Iron (Fe) mg/kg 14000 6600 9300 14000 15000 9100 11000 10000 9400 9000 8400 47,766
24
Acid Extractable Lead (Pb) mg/kg 34 8.8 30 49 24 8 43 13 13 8.9 17 35 91.3 91.3
Acid Extractable Lithium (Li) mg/kg 17 8 15 10 9.7 4.9 8.9 11 14 13 12
Acid Extractable Manganese (Mn) mg/kg 540 230 260 480 1300 430 380 1000 290 460 420 1,100
Acid Extractable Mercury (Hg) mg/kg 0.27 0.15 0.25 0.27 0.2 0.12 0.21 0.16 ND 0.12 0.14 0.17 0.486 0.486
Acid Extractable Molybdenum
(Mo) mg/kg ND ND <2
(ND) ND 2 ND <2
(ND) ND ND 2 <2
(ND)
Acid Extractable Nickel (Ni) mg/kg 10 4.9 8 7.5 6.9 4.3 5.8 5.7 4.6 8.7 7.2 75
Acid Extractable Phosphorus
(P) mg/kg 1900 1600 1900 2200 1600 400 490 1700
Acid Extractable Rubidium
(Rb) mg/kg 11 5.9 9.5 6.3 6.2 3.5 5.2 4.7 5.5 7 6.5
Acid Extractable Selenium
(Se) mg/kg 1.3 0.89 1.2 1.8 1.8 1.1 1.5 ND ND 1.7 1.5 2
Acid Extractable Silver (Ag) mg/kg ND ND <0.5 (ND) ND ND ND <0.5 (ND) ND ND ND <0.5 (ND) 1
Acid Extractable Strontium
(Sr) mg/kg 13 6.1 9.3 13 13 8.1 9.6 ND ND 8.7 7.8
Acid Extractable Thallium (Tl) mg/kg 0.26 0.13 0.18 0.26 0.24 0.13 0.17 0.34 0.11 0.31 0.21
Acid Extractable Tin (Sn) mg/kg 2.5 ND 2 3 1.5 ND 2.1 2 ND ND 1.1
Acid Extractable Uranium (U) mg/kg 4.3 2.6 3.5 5.7 6.5 3.7 4.3 1.7 2 7.3 5.7
Acid Extractable Vanadium (V) mg/kg 23 12 17 30 34 21 25 11 12 24 22
Acid Extractable Zinc (Zn) mg/kg 87 46 71 93 89 48 70 96 66 110 100 123 315 315
Orthophosphate (P) mg/kg 0.15 0.39 0.51 0.067 0.086 0.27 0.24 0.26 0.24 0.24 0.26
25
Table 2. Concentrations of metals within stream site sediment samples.
UNITS Forties
River
Zwicker
Brook
Sherbrooke
River
Pine Lake
Brook
Concentration
Guidelines
Metals 2018 2019 2021 2022 ISQG PEL NS
Acid Extractable Aluminum (Al) mg/kg 4300 4700 3300 730
Acid Extractable Antimony (Sb) mg/kg ND ND ND ND 25
Acid Extractable Arsenic (As) mg/kg 2.7 ND ND ND 5.9 17 17
Acid Extractable Barium (Ba) mg/kg 26 18 18 ND
Acid Extractable Beryllium (Be) mg/kg ND ND ND ND
Acid Extractable Bismuth (Bi) mg/kg ND ND ND ND
Acid Extractable Boron (B) mg/kg ND ND ND ND
Acid Extractable Cadmium (Cd) mg/kg ND ND ND ND 0.6 3.5 3.5
Acid Extractable Chromium (Cr) mg/kg 4.7 4 4 ND 37.3 90 90
Acid Extractable Cobalt (Co) mg/kg 2.3 2.2 1.9 ND
Acid Extractable Copper (Cu) mg/kg ND 4.2 ND ND 35.7 197 197
Acid Extractable Iron (Fe) mg/kg 8300 6800 5800 1200 47,766
Acid Extractable Lead (Pb) mg/kg 3.3 3.3 4.2 1 35 91.3 91.3
Acid Extractable Lithium (Li) mg/kg 20 21 16 4.1
Acid Extractable Manganese (Mn) mg/kg 200 110 150 40 1,100
Acid Extractable Mercury (Hg) mg/kg ND ND ND ND 0.17 0.486 0.486
Acid Extractable Molybdenum (Mo) mg/kg ND ND ND ND
Acid Extractable Nickel (Ni) mg/kg 2.3 3.1 2.2 ND 75
Acid Extractable Phosphorus (P) mg/kg 180 190 ND
Acid Extractable Rubidium (Rb) mg/kg 17 7.8 11 3.1
Acid Extractable Selenium (Se) mg/kg ND ND ND ND 2
26
Acid Extractable Silver (Ag) mg/kg ND ND ND ND 1
Acid Extractable Strontium (Sr) mg/kg ND ND ND ND
Acid Extractable Thallium (Tl) mg/kg 0.12 ND ND ND
Acid Extractable Tin (Sn) mg/kg ND ND ND ND
Acid Extractable Uranium (U) mg/kg 0.52 0.77 0.46 0.17
Acid Extractable Vanadium (V) mg/kg 11 9 7.3 ND
Acid Extractable Zinc (Zn) mg/kg 20 34 20 ND 123 315 315
Orthophosphate (P) mg/kg 0.28 0.38 0.36 0.79
27
Table 3. Summary of guideline exceedances of metals in sediment samples. Light yellow indicates parameters approaching one
of the guidelines, orange indicates an exceedance of the ISQG, and red indicates an exceedance of either the PEL or NSEQS
guidelines
UNITS Lake 1 Lake 2 Lake 3 Lake 4
Metals 2019 2021 2022 2018 2019 2021 2022 2018 2019 2021 2022
Acid Extractable Arsenic (As) mg/kg 8.4 4.8 6.8 16 12 6.8 12 8.3 8.1 9.8 8.3
Acid Extractable Cadmium (Cd) mg/kg 0.76 0.31 0.69 1 0.99 0.46 0.81 1.5 0.76 0.63 0.66
Acid Extractable Lead (Pb) mg/kg 34 8.8 30 49 24 8 43 13 13 8.9 17
Acid Extractable Mercury (Hg) mg/kg 0.27 0.15 0.25 0.27 0.2 0.12 0.21 0.16 ND 0.12 0.14
2.4.2 Sediment Phosphorus and Orthophosphate
Concentrations of both acid-extractable (total) phosphorus and bioavailable orthophosphate
in sediment were analyzed from 2018 to 2022, with total phosphorus being excluded from
the 2021 sample.
Table 4. Orthophosphate and Total Phosphorus levels from the annual sediment samples at the Lake and Stream Sites. FR =
Forties River; ZB = Zwicker Brook; SR = Sherbrooke River; PLB = Pine Lake Brook.
Lake 1 Lake 2 Lake
3
Lake 4 FR ZB SR PLB
Parameter
(Units)
2019 2021 2022 2018 2019 2021 2022 2018 2019 2021 2022 2018 2019 2021 2022
Orthophosphate
in sediment
(mg/kg)
0.15 0.39 0.51 0.0067 0.086 0.27 0.24 0.26 0.24 0.24 0.26 0.33 0.38 0.36 0.79
Acid extractable
phosphorus in
sediment
(mg/kg)
1900 1600 1900 2200 1600 400 490 1700 180 190 ND
28
Orthophosphate levels increased at all sites in 2022, except for Lake 2, which had a decrease
of 0.03 in 2022. The sample results from Pine Lake Brook showed higher levels of
orthophosphate than the three other stream sites sampled in previous years. According to
Ontario’s provincial sediment quality guidelines, pollution can range from clean/marginally
polluted (‘lowest effect level’) at 600 mg/kg of phosphorus to heavily contaminated (‘severe
effect level’) at >2000 mg/kg of phosphorus in sediment (Ontario MOE 2008). These
guidelines have previously been approached and exceeded at Lake 1, Lake 2, and Lake 4, but
not Lake 3 or stream sites.
Orthophosphate is a bioavailable form of phosphorus that 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). 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 a turnover when nutrient-rich
bottom waters are mixed throughout the lake, providing new food sources for organisms.
3.0 Discussion
Similar to 2018, 2019, and 2021 monitoring results, the water quality of Sherbrooke Lake
and its tributaries did not identify any significant water quality issues in 2022. Only one
bloom was reported in SL in 2022; however, sampling blooms and determining their toxicity
remains a challenge. All visible blooms should be treated with caution and ongoing efforts
will continue to improve the reporting and advisory process.
3.1 Algae Blooms in Sherbrooke Lake
NS Environment’s current system of notifying lake residents of potentially harmful algae
blooms is reactive and can be ineffective. NSE responds to reports of suspected blooms but
inspectors are not always able to respond in time to witness the bloom. NSE rarely collects
water samples for analysis and often has to post precautionary advisories based on the
appearance of a bloom in photographs from residents. Lake closure advisories are posted via
Twitter and other online locations.
29
Microcystin-LR is not the only toxin produced by cyanobacteria. Anatoxins,
Cylindrospermopsins, Nodularins, Saxitoxins, Dermatoxtoxins, and other irritant toxins are
also produced by cyanobacteria (Health Canada 2012). The majority of commercial labs in
Canada do not test for these toxins. This means that the absence of Microcystin-LR in a water
sample does not mean that a bloom does not contain other toxins. Because of this, lake
residents should be made aware of all blooms and treat all blooms with the same level of
caution.
As algal blooms can be induced and intensified by increases in nutrients to ecosystems
(whether naturally from the mixing of waters or anthropogenically from pollution), trends
in algal blooms are hard to predict and can vary spatially. The literature predicts increases
in both size and frequency of blooms, globally, in the future (Michalak et al. 2013). Although
nitrogen and phosphorus levels remain low, algal blooms should continue to be monitored
and tested within Sherbrooke Lake, with residents made aware of algal bloom causes, health
effects, precautions to take, and the reporting procedure if a bloom occurs.
3.2 Trophic State of Sherbrooke Lake
The biological productivity of SL has been assessed and monitored for changes over time by
identifying its trophic state annually. Based on the mean depth of transparency (Secchi disk),
and mean concentrations of chlorophyll-α and phosphorus, a Trophic State Index (TSI) score
can be calculated using the Carlson (1977) equations (Equations 1, 2, and 3). Trophic states
range from oligotrophic (low productivity and minimal biomass) to hypereutrophic (high
productivity and maximum biomass). The following information was based on data collected
from Lake sites 1, 2, and 4 in June, August and September of 2022.
Equation 1: 𝑆𝑆𝐼 (𝑆𝑐𝑐𝑐𝑖ℎ 𝑐�ℎ𝑟𝑘)=60 −14.41 × 𝑘𝑘(𝑀𝑐𝑎𝑘 𝑆𝑐𝑐𝑐𝑖ℎ 𝑐�ℎ𝑟𝑘 [𝑘])
Equation 2: 𝑆𝑆𝐼 (𝐶�𝑘𝑘𝑟𝑘𝑘�𝑦𝑘𝑘 𝐴)=30.6 +9.81 × 𝑘𝑘(𝑀𝑐𝑎𝑘 𝐶�𝑘𝑘𝑟𝑘𝑘�𝑦𝑘𝑘 𝑎 [𝜇𝑔
𝐿])
Equation 3: 𝑆𝑆𝐼 (𝑆𝑘𝑟𝑎𝑘 𝑃�𝑘𝑟𝑘�𝑘𝑟𝑟𝑟)=4.15 +14.42 × 𝑘𝑘(𝑀𝑐𝑎𝑘 𝑆𝑘𝑟𝑎𝑘 𝑃�𝑘𝑟𝑘�𝑘𝑟𝑟𝑟 [𝜇𝑔
𝐿])
30
Table 5. TSI values for all lake sites in 2022 for three parameters.
Parameter Calculated TSI Value
Secchi disk
(transparency)
40.85
Chlorophyll-α 45.37
Total Phosphorus 31.11
TSI Value 39.11
Figure 28. Carlson TSI for Sherbrooke Lake in 2022 using the mean Secchi disk depth (transparency), mean chlorophyll α
concentration and mean total phosphorus concentration. (Carlson 1977)
31
The trophic state of SL in 2018 and 2019 was oligotrophic-mesotrophic. The transition from
oligotrophic to mesotrophic is a TSI score of 40. In 2018 and 2019, the TSI was less than a
10th of a decimal over 40, therefore classifying the lake as mesotrophic. In 2021, the TSI score
was 39.4, putting the lake into an oligotrophic state. The trophic state has remained
oligotrophic in 2022, with a TSI score of 39.11. SL appears to be maintaining a steady TSI
score over the four years this data has been collected (Figure 29). The Total Phosphorus
remains the lowest of all TSI scores every year, while the Chlorophyll-a TSI score is the
highest. Secchi depth readings are highly influenced by several factors; therefore, the TSI
score for Total Phosphorus should be considered the most accurate reflection of biological
productivity in SL, resulting in an oligotrophic status.
Figure 29. Comparison of Lake site TSI scores from 2018 to 2022 using the Carlson (1977) trophic equations for total
phosphorus, chlorophyll α, and Secchi disk (2020 excluded).
20
25
30
35
40
45
50
55
2017 2018 2019 2020 2021 2022 2023
TS
I
V
a
l
u
e
TSI Secchi Chl-a TP
32
4.0 Recommendations
The following recommendations are suggested for the Sherbrooke Lake Water Quality
Monitoring Program:
1. The Sherbrooke Lake Water Quality Monitoring Program should continue in 2023 as
this program was developed to establish a water quality baseline to aid in evidence-based
decisions concerning the development of the public access property acquired by MODL for
public use. Development at this site has yet to begin, meaning that further monitoring will
continue to establish a baseline understanding of SL water quality before the potential
impacts of this development start. The 2023 monitoring program will be the 5th and final
year of baseline monitoring, as outlined in the initial project proposal.
2. When MODL decides to move forward with the park development and if they decide
to re-establish the public access site planning committee, this committee should meet with
the SLSC members to receive an update on the water quality program that was managed by
SLSC and to discuss future monitoring activities that should be conducted. Any
recommendations from these two committees would need to be presented to both the MODL
and MODC councils.
3. Attempts should be made to identify a lake resident willing and able to host the SL
weather station. The station should be installed as early as possible in the monitoring season
and checked monthly to ensure it is working properly.
4. Monitoring of the seven inlet streams should continue during rainfall-dependent
events, to determine how rainfall is affecting inlet streams.
5. Volunteer monitors should continue to be supplied with bottles for Microcystin-LR
sample collection.
6. Algae blooms should continue to be monitored, recorded, and reported to Nova Scotia
Environment. Efforts should continue to improve the reporting and advisory process
between the NS Department of Environment and Climate Change, municipal units, and SL
cottage associations.
7. Depth profiles at all lake sites should be continued during regular monitoring activity
given the varying strength and depth of the thermocline observed at these sites in previous
years and considering the elevated nutrient concentrations observed in deeper waters.
8. Sediment total phosphorus should be included in the final year of sampling. BV labs
now require a separate analysis for this parameter.
33
5.0 Acknowledgements
This project is funded by the Municipality of the District of Lunenburg (MODL) and the
Municipality of Chester (MOC). Coastal Action would like to thank the volunteers and
Sherbrooke Lake Stewardship Committee for their contributions that made for a successful
2022 field season.
34
6.0 References
Canadian Council of Ministers of the Environment (CCME). 1999. Canadian water quality
guidelines for the protection of aquatic life: Dissolved oxygen (Freshwater). In: Canadian
environmental quality guidelines, 1999, Canadian Council of Ministers of the Environment,
Winnipeg.
Canadian Council of Ministers of the Environment (CCME). 2002. Canadian water quality
guidelines for the protection of aquatic life: Total particulate matter. In: Canadian
environmental quality guidelines, 1999, Canadian Council of Ministers of the Environment,
Winnipeg.
Carlson, R. E. 1977. A trophic state index for lakes. Limnol. Oceanogr., 22(2), 361-369.
Dodds, W.K. and Welch, E.B. 2000. Establishing nutrient criteria in streams. J. N. Am. Benthol.
Soc., 19(1), 186-196.
Genzoli, L. and Kann, J. 2016. Evaluation of phycocyanin probes as a monitoring tool for
toxigenic cyanobacteria in the Klamath River below Iron Gate Dam.
10.13140/RG.2.2.23897.31841.
Hayes, F.R., Reid, B.L, and Cameron, M.L. 1985. Lake water and sediment. Limnol. Oceanogr,
3, 308-317.
Health Canada. 2012. Guidelines for Canadian recreational water quality, Third Edition.
Water Air, and Climate Change Bureau, Healthy Environments and Consumer Safety Branch,
Health Canada, Ottawa, Ontario. (Catalogue No H129-15/2012E).
Hinch, P.R. and Underwood, J.K. 1985. A study of aquatic conditions in Lake Echo during
1984. N.S. Dept. Env. Lib. L192.1 85/00 C2. 38 p.
Jones, G.J. and Orr, P.T. 1994. Release and degradation of microcystin following algicide
treatment of a Microcystis aeruginosa bloom in a recreational lake, as determined by HPLC
and protein phosphatase inhibition assay. Water Res., 28: 871–876.
Michalak, A.M., Anderson, E.J., Beletsky, D., Boland, S., Bosch, N.S., Bridgeman, T.B., Chaffin,
J.D., Cho, K., Confesor, R., Daloğlu, I. and DePinto, J.V. 2013. Record-setting algal bloom in Lake
Erie caused by agricultural and meteorological trends consistent with expected future
conditions. P. Natl. Acad. Sci., 201216006.
Nova Scotia Environment (NSE). 2014. Environmental Quality Standards for Contaminated
Sites, Rationale and Guidance Document. Version 1.0, April 2014. 57 p.
35
Nova Scotia Salmon Association (NSSA) NSLC Adopt-A-Stream Program. 2014. Walking the
river: A citizen’s guide to interpreting water quality data. 43 p.
Nova Scotia Salmon Association (NSSA) NSLC Adopt-a-Stream Program. 2015. Acid Rain.
[http://www.nssalmon.ca/issues/acid-rain].
Ontario Ministry of the Environment (MOE). 1979. Rationale for the establishment of
Ontario’s provincial water quality objectives. Queen’s Printer for Ontario. 236 p.
Ontario Ministry of the Environment (MOE). 2008. Guidelines for identifying, assessing and
managing contaminated sediments in Ontario. Queen’s Printer for Ontario. 112 p.
Søndergaard, M., Jensen, J. P., and Jeppesen, E. 2003. Role of sediment and internal loading of
phosphorus in shallow lakes. Hydrobiologia, 506(1-3), 135-145.