HomeMy Public PortalAbout2018_Report_Sherbrooke Lake_Water Quality MonitoringSherbrooke Lake
2018 Water Quality Monitoring Report
Prepared for
Municipality of Chester
Municipality of the District of Lunenburg
Sherbrooke Lake Stewardship Committee
By
Bluenose Coastal Action Foundation
37 Tannery Road, PO Box 730
Lunenburg, N.S.
B0J 2C0
December 2018
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Table of Contents
1. Introduction .......................................................................................................................................... 6
1.1. Sherbrooke Lake Background ....................................................................................................... 6
1.2. Program Background .................................................................................................................... 7
1.3. Objectives and Scope of Work .................................................................................................... 10
2. Water Quality Monitoring Results ...................................................................................................... 10
2.1. Physical Water Parameters ......................................................................................................... 10
2.1.1. Surface Water Temperature ............................................................................................... 10
2.1.2. Surface Dissolved Oxygen ................................................................................................... 12
2.1.3. Depth Profiles...................................................................................................................... 13
2.1.4. pH ........................................................................................................................................ 16
2.1.5. Total Dissolved Solids .......................................................................................................... 18
2.2. Chemical Water Parameters ....................................................................................................... 20
2.2.1. Total Suspended Solids ....................................................................................................... 20
2.2.2. Total Phosphorus ................................................................................................................ 22
2.2.3. Total Nitrogen ..................................................................................................................... 25
2.2.4. Hydrocarbons ...................................................................................................................... 27
2.2.5. Chlorophyll a ....................................................................................................................... 27
2.2.6. Fecal Coliform Bacteria ....................................................................................................... 28
2.3. Sediment Sampling ..................................................................................................................... 30
3. Discussion ............................................................................................................................................ 33
3.1. Trophic State of Sherbrooke Lake ............................................................................................... 33
3.2. Algal Blooms ................................................................................................................................ 35
3.3. Pollution ...................................................................................................................................... 35
4. Recommendations .............................................................................................................................. 36
5. References .......................................................................................................................................... 37
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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). .................................................................... 6
Figure 2: Sherbrooke Lake 2018 Water Quality Monitoring Program sampling locations. .......................... 8
Figure 3: Water temperatures at four monthly lake sites (Lake 1-4), and two summer-only sites (Chl 1
and Chl 2) during the May-October 2018 SL water quality field season. ................................................... 11
Figure 4: 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). ..................................................................................... 11
Figure 5: DO at four monthly lake sites (Lake 1-4), and two summer-only sites (Chl 1 and Chl 2) during
the May-October 2018 SL water quality field season. ................................................................................ 12
Figure 6: 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). .................................................................................................................. 13
Figure 7: Water temperature depth profile from two lakes during the August 2018 sampling of SL. ....... 14
Figure 8: DO depth profile from two lake sites during the August 2018 sampling of SL. ........................... 15
Figure 9: Four common water temperature and DO depth profiles, from Hutchinson, 1957. .................. 15
Figure 10: pH at four monthly lake sites (Lake 1-4), and two summer-only sites (Chl 1 and Chl 2) during
the May-October 2018 SL water quality field season. ................................................................................ 17
Figure 11: 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). ......................................................................................................... 17
Figure 12: TDS at four monthly lake sites (Lake 1-4), and two summer-only sites (Chl 1 and Chl 2) during
the May-October 2018 SL water quality field season. ................................................................................ 19
Figure 13: 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). ......................................................................................................... 19
Figure 14: TSS at four monthly lake sites (Lake 1-4) during the May-October 2018 SL water quality field
season. ........................................................................................................................................................ 21
Figure 15: 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). ......................................................................................................... 21
Figure 16: Total phosphorus at four monthly lake sites (Lake 1-4) during the May-October 2018 SL water
quality field season. .................................................................................................................................... 23
Figure 17: 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). ..................................................................................... 23
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Figure 18: Total nitrogen at four monthly lake sites (Lake 1-4) during the May-October 2018 SL water
quality field season. .................................................................................................................................... 25
Figure 19: 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). ..................................................................................... 26
Figure 20: Chlorophyll a at four monthly lake sites (Lake 1-4), and two summer-only sites (Chl 1 and Chl
2) during the May-October 2018 SL water quality field season. ................................................................ 28
Figure 21: Fecal coliform at four monthly lake sites (Lake 1-4) during the May-October 2018 SL water
quality field season. .................................................................................................................................... 29
Figure 22: Fecal coliform 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). ..................................................................................... 30
Figure 23: Carlson TSI for lakes, with TSI ranks for SL Lake 1 (red star) and Lake 2 (blue star).
Transparency determined using Secchi disk depth. From Carlson (1977). ................................................ 34
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List of Tables
Table 1: Monitoring program parameters, site locations, and sampling frequencies for the 2018
Sherbrooke Lake Water Quality Monitoring Program. New coordinates to access river sites via road are
in blue. .......................................................................................................................................................... 9
Table 2: Mean and maximum TDS concentrations from lake and river sites during the 2018 SL field
season. ........................................................................................................................................................ 18
Table 3: Range in total phosphorus concentrations between 2017 and 2018; July-August for lake
samples, August for river samples. ............................................................................................................. 24
Table 4: Total phosphorus concentrations from two lake sites, obtained both at the surface and below
the thermocline, in August for the SL 2018 Water Quality Monitoring Program....................................... 24
Table 5: Range in total nitrogen concentrations between 2017 and 2018; July-August for lake samples,
August for river samples. ............................................................................................................................ 26
Table 6: Total nitrogen concentrations from two lake sites, obtained both at the surface and below the
thermocline, in August for the SL 2018 Water Quality Monitoring Program. ............................................ 27
Table 7: Concentration of metals within site sediment samples sampled on August 27th, 2018. 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.
.................................................................................................................................................................... 32
Table 8: Comparison of 2018 sediment metal concentrations from SL Lake 2, Lake 3, and Forties River to
the range and mean metal concentrations from four Kejimkujik Lakes (Hilchemakaar, Big Dam East,
Cobrielle, and Peskowesk) monitored from 2000-2009 (Kirk, 2018). ......................................................... 33
Table 9: Phosphorus concentrations in sediment samples from lake and river sites sampled on August
27th, 2018. ................................................................................................................................................... 33
Table 10: Carlson (1977) 2018 SL TSI scores and trophic states for total phosphorus, chlorophyll A, and
Secchi disk for Lake 1 (red) and Lake 2 (blue). ............................................................................................ 34
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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 South-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 of the status of the
watershed and the individual sites is reported annually and available at the Coastal Action website
(http://coastalaction.org/Wordpress/).
Forestry, silviculture, and agriculture dominate the LaHave River watershed and SL sub-watershed. 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).
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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 determined to be 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 Bluenose Coastal Action Foundation (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 Sherbrooke Lake 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.
Although a preliminary monitoring program was implemented in 2017, the full Sherbrooke Lake Water
Quality Monitoring Program began in May 2018. The 2018 monitoring program consisted of three lake
sites monitored for various chemicals monthly from May to October, two additional lake sites monitored
during the summer months for chlorophyll a, four streams monitored bimonthly from May to October,
seven streams monitored once after a rainfall event (>20 mm rainfall within 24 hours), two lake sites
and one stream site where one-time sediment samples were obtained for analyses, and two lake sites
where one-time lake profiles and nutrients at-depth were obtained for analyses (Figure 2, Table 1). The
2018 monitoring program incorporated trained volunteers to collect the water and sediment samples
throughout the field season, while Coastal Action coordinated the sampling and analyzed the data (for
full methodology please refer to the Sherbrooke Lake Water Quality Monitoring Program available upon
request from either the Municipality of Chester or the Municipality of the District of Lunenburg).
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Figure 2: Sherbrooke Lake 2018 Water Quality Monitoring Program sampling locations.
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Table 1: Monitoring program parameters, site locations, and sampling frequencies for the 2018 Sherbrooke Lake Water Quality
Monitoring Program. New 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, fecal coliform,
chlorophyll a, Secchi disk depth. One-time depth
profile.
Lake 2 376072 E, 4943018 N Monthly (May-
Oct.)
YSI, hydrocarbons, total suspended solids, total
phosphorus, total nitrogen, fecal coliform,
chlorophyll a, Secchi disk depth. One-time dept
profile and sediment grab.
Lake 3 (Public
Access)
376831 E, 4943540 N Monthly (May-
Oct.)
YSI, hydrocarbons, total suspended solids, total
phosphorus, total nitrogen, fecal coliform,
chlorophyll a, Secchi disk depth. One-time
sediment grab.
Lake 4* (Public
Access Boat
Launch)
376844 E, 4943371 N Monthly (Sept –
Oct.)
YSI, hydrocarbons, total suspended solids, total
phosphorus, total nitrogen, fecal coliform,
chlorophyll a.
Chl 1 371682 E, 4949984 N Monthly (June-
Aug.)
YSI, chlorophyll a, Secchi disk depth.
Chl 2 372466 E, 4949027 N Monthly (June-
Aug.)
YSI, chlorophyll a, Secchi disk depth.
Butler Lake
Brook
370079 E, 4952036 N One-time, rainfall-
dependent
YSI, total suspended solids, total phosphorus,
total nitrogen, fecal coliform, chlorophyll a.
Sherbrooke
River
370845 E, 4952984 N
369774 E, 4954072 N
Bi-monthly (May,
July, Sept.) &
rainfall-dependent
YSI, total suspended solids, total phosphorus,
total nitrogen, fecal coliform, chlorophyll a.
Gully River 372050 E, 4953315 N
372246 E, 4953404 N
One-time, rainfall-
dependent
YSI, total suspended solids, total phosphorus,
total nitrogen, fecal coliform, chlorophyll a.
Forties River 373210 E, 4949840 N
373539 E, 4949823 N
Bi-monthly (May,
July, Sept.) &
rainfall-dependent
YSI, total suspended solids, total phosphorus,
total nitrogen, fecal coliform, chlorophyll a. One-
time sediment grab.
Pine Lake
Brook
373705 E, 4945670 N Bi-monthly (May,
July, Sept.) &
rainfall-dependent
YSI, total suspended solids, total phosphorus,
total nitrogen, fecal coliform, chlorophyll a.
Zwicker Brook 376582 E, 4944469 N Bi-monthly (May,
July, Sept.) &
rainfall-dependent
YSI, total suspended solids, total phosphorus,
total nitrogen, fecal coliform, chlorophyll a.
Peter Veinot
Brook
376552 E, 4942058 N
376507 E, 4941558 N
One-time, rainfall-
dependent
YSI, total suspended solids, total phosphorus,
total nitrogen, fecal coliform, 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.
*Lake 4 site added in September 2018 after a Sherbrooke Park Design Meeting to obtain water quality specifically at the lake site near the
planned boat launch.
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1.3. 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 2018 Water Quality Monitoring Program
● Ordering and ensuring correct bottles from Maxxam Analytics
● Creating and printing waterproof field sheets for each sampling month
● Implementing two days of volunteer training
● Calibrating and caring for the MODL-MOC YSI monthly
● Ensuring volunteers obtained all required field equipment for field work
● Transferring data from field sheets and Maxxam into a database and analyzing data
● Attending SLSC meetings and presenting water quality results
● Preparing this report to summarize results and recommendations for water quality related to
Sherbrooke Lake
2. Water Quality Monitoring Results
2.1. Physical Water Parameters
2.1.1. 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 10.2-26.7oC, while streams ranged from 13-26.5oC (Figures 3
and 4). The lake sites exceeded 20oC between June to August 2018, while the stream sites exceeded
20oC in July and August 2018. In the lake, surface temperatures exceeding 20oC will not greatly affect
organisms, as aquatic life can take refuge in the cooler deep waters below; however, this is not the case
for streams. The highest water temperatures were recorded at Sherbrooke River and Forties River. The
lower temperatures observed at Pine Lake Brook and Zwicker Brook may be due to higher percentage of
shade covering the waters (from tree canopies) due to smaller stream widths (compared to Sherbrooke
and Forties). Pine Lake Brook and Zwicker Brook exceeded that 20oC threshold only once (by 0.1oC in
July 2018) – these streams appear to provide a suitable habitat for aquatic organisms year-round.
Following the one-time rainfall sampling event, 5/7 streams were below 20oC, with only Sherbrooke and
Forties exceeding the threshold.
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Figure 3: Water temperatures at four monthly lake sites (Lake 1-4), and two summer-only sites (Chl 1 and Chl 2) during the May-
October 2018 SL water quality field season. Red line indicates the 20oC limit for survival of aquatic organisms.
Figure 4: 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).
Red line indicates the 20oC limit for survival of aquatic organisms.
0
5
10
15
20
25
30
Temperature (oC)Lake 1 Lake 2 Lake 3 Lake 4 Chl 1 Chl 2
0
5
10
15
20
25
30
Temperature (oC)Sherbrooke River Forties River Pine Lake Brook Zwicker Brook
Butler Lake Brook Gully River Peter Veinot Brook
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2.1.2. 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 at ≥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 also is 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).
Of the lake and stream sites, only one stream site had DO below 6.5 mg/L throughout the 2018 field
season (Figures 5 and 6). The six lake sites monitored in SL were always >7 mg/L, even as DO decreased
during summer months due to biological demand. The high DO concentrations may be attributed to the
sampling depths for these monthly and bimonthly samples, as only surface water was monitored and
therefore influenced by the DO engulfment via winds and waves. The seven stream sites also appear to
be well oxygenated and suitable for aquatic life – even the Peter Veinot Brook measurement below 6.5
mg/L was only 0.09 mg/L below the threshold.
Figure 5: DO at four monthly lake sites (Lake 1-4), and two summer-only sites (Chl 1 and Chl 2) during the May-October 2018 SL
water quality field season. Red line indicates CCME’s 6.5 mg/L DO minimum-threshold for survival of aquatic organisms.
4
5
6
7
8
9
10
11
12
Dissolved Oxygen (mg/L)Lake 1 Lake 2 Lake 3 Lake 4 Chl 1 Chl 2
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Figure 6: 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.
2.1.3. Depth Profiles
2.1.3.1. At-Depth Water Temperature
The water profile at lake sites 1 and 2 in August 2018 indicate that both sites have a thermal
stratification – Lake 2 having a stronger stratification than Lake 1 (Figure 7). Stratification begins at a
shallower depth (5 m) for Lake 2 than Lake 1 (8 m). Lake 2’s thermocline is 8 m thick, separating the
>20oC surface waters from the <10oC deep waters. Lake 1’s thermocline is only 2 m thick, with ~5oC
separation between surface and deep waters. 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 inhibit mixing.
4
5
6
7
8
9
10
11
12
Dissolved Oxygen (mg/L)Sherbrooke River Forties River Pine Lake Brook Zwicker Brook
Butler Lake Brook Gully River Peter Veinot Brook
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Figure 7: Water temperature depth profile from two lakes during the August 2018 sampling of SL. Red line indicates the 20oC
limit for survival of aquatic organisms.
2.1.3.2. 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 8). Of the four common DO profiles in lakes (Figure 9), Lake 1 presents a clinograde
curve, where DO is highest in the surface waters and lowest in the deep waters. Clinograde curves often
occur in mesotrophic and eutrophic lakes, where microbial decomposition uses and depletes the lake’s
DO. Lake 2 appears 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.
There is a drop of DO at the base of the lake in Lake 2 - this may be due to increased microbial presence
– again due to increased nutrients available (decaying organisms and litter would sink to the sediment,
acting as a food source of microbes).
0
5
10
15
20
25
30
0 5 10 15 20 25
Depth (m)Temperature (oC)
Lake 1 Lake 2
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Figure 8: DO depth profile from two lake sites during the August 2018 sampling of SL. Red line indicates CCME’s 6.5 mg/L DO
minimum-threshold for survival of aquatic organisms.
Figure 9: Four common water temperature and DO depth profiles, from Hutchinson, 1957.
0
5
10
15
20
25
30
0 1 2 3 4 5 6 7 8 9
Depth (m)Dissolved Oxygen (mg/L)
Lake 1 Lake 2
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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
available. 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 the water’s DO is replenished during fall turnover.
It appears at the bottom of the lake at both Lake 1 and 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). 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.
2.1.4. pH
pH is a parameter used to access 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
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 2018 SL monitoring program varied between 3.2-6.6 (Figures 10
and 11). Lake 3 consistently had the highest pH values, while only Lake 2 and Lake 4 fell below 5.5 (4.22
and 3.24, respectively). It is unclear what caused Lake 4’s pH to drop to 3.24 during the October
sampling, and more data is required to understand if the pH of this site is commonly acidic, or if this was
an anomaly. Of the stream sites, the lowest recorded pH was 5.05 at Pine Lake Brook – Pine Lake Brook
was consistently one of the lowest pH sites during the 2018 field season.
Even with pH values below the CCME’s 6.5-pH threshold at lake and river sites, the data suggest that pH
would not negatively affect aquatic life in the streams and most lake sites. For the stream sites, pH >5.0
is adequate for the survival of fish and invertebrates (Morris, Taylor, and Brown, 1989). Of the lake sites,
only Lake 2 and Lake 4 pose a threat to aquatic life; however, as the length of the low-pH conditions are
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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.
Figure 10: pH at four monthly lake sites (Lake 1-4), and two summer-only sites (Chl 1 and Chl 2) during the May-October 2018 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).
Figure 11: 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). Red line
indicates the 5.0-pH minimum threshold for survival of fish and invertebrates (Morris, Taylor, and Brown, 1989).
3
3.5
4
4.5
5
5.5
6
6.5
7
pHLake 1 Lake 2 Lake 3 Lake 4 Chl 1 Chl 2
3
3.5
4
4.5
5
5.5
6
6.5
7
pHSherbrooke River Forties River Pine Lake Brook Zwicker Brook
Butler Lake Brook Gully River Peter Veinot Brook
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2.1.5. 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 a 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 2, Figures 12 and 13). TDS was very similar between lake sites, while streams had slightly
more TDS concentration variation between sites. Of the four bimonthly stream sites monitored, no site
indicated an increase in TDS during the rainfall sampling event. Butler Brook had the highest recorded
TDS concentration (39 mg/L), which is consistent with its 2017 preliminary data (33.8 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.
Table 2: Mean and maximum TDS concentrations from lake and river sites during the 2018 SL field season.
Site Type Site Mean TDS (mg/L) Maximum TDS (mg/L)
Lake
Lake 1 18.8 20.0
Lake 2 18.2 19.0
Lake 3 18.2 19.0
Lake 4 18.5 19.0
Chl 1 19.0 20.0
Chl 2 18.3 19.0
Stream
Sherbrooke River 21.3 23
Forties River 19.0 24
Pine Lake Brook 17.9 21
Zwicker Brook 19.0 23
Butler Brook - 39
Gully River - 14
Peter Veinot Brook - 21
19 | Page
Figure 12: TDS at four monthly lake sites (Lake 1-4), and two summer-only sites (Chl 1 and Chl 2) during the May-October 2018
SL water quality field season.
Figure 13: 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).
0
5
10
15
20
25
30
35
40
45
50
Total Dissolved Solids (mg/L)Lake 1 Lake 2 Lake 3 Lake 4 Chl 1 Chl 2
0
5
10
15
20
25
30
35
40
45
50
Total Dissolved Solids (mg/L)Sherbrooke River Forties River Pine Lake Brook Zwicker Brook
Butler Lake Brook Gully River Peter Veinot Brook
20 | Page
2.2. Chemical Water Parameters
2.2.1. 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 3.4 mg/L for SL lake and river sites (Figures 14 and 15). Most
lake sites had <1 mg/L of TSS during the field season, with minimal differences between lake sites. For
the stream sites, Zwicker Brook had, in general, the highest TSS concentrations; however, Sherbrooke
River did have the highest TSS of the 2018 field season (3.4 mg/L). The high TSS concentration at
Sherbrooke River coincides with the rainfall-dependent event; however, no other stream experienced
increased TSS during the rainfall event. 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.
Secchi disk depth – the depth to which a black and white disk just is 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. Lake 1 was
visible to a maximum depth of 2.65 m, with a mean depth of 2.21 m. Lake 2 had a maximum visible
depth of 2.84 m and mean depth of 2.43 m. At Lake 3 and 4, the Secchi depths were equivalent to the
depth of water, due to the shallowness of the sites (mean depth of 1.78 m and 2.38 m, respectively).
Although Secchi depth provides an indication of light penetration into waterbodies, the measurements
can be skewed due to an individual’s eyesight, and different individuals performing the measurement on
different days.
21 | Page
Figure 14: TSS at four monthly lake sites (Lake 1-4) during the May-October 2018 SL water quality field season.
Figure 15: 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).
0
0.5
1
1.5
2
2.5
3
3.5
4
Total Suspended Solids (mg/L)Lake 1 Lake 2 Lake 3 Lake 4
0
0.5
1
1.5
2
2.5
3
3.5
4
Total Suspended Solids (mg/L)Sherbrooke River Forties River Pine Lake Brook Zwicker Brook
Butler Lake Brook Gully River Peter Veinot Brook
22 | Page
2.2.2. 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 high demand of phosphorus by plants, phosphorus concentrations
are low in 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 located 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.
Lake sites were consistently lower than streams (Figures 16 and 17, Table 3). Lake phosphorus
concentrations ranged from <0.004 mg/L to 0.017 mg/L, while streams ranged from 0.011 mg/L to 0.04
mg/L. No lake phosphorus concentrations exceeded the MOECC lake guideline of 0.02 mg/L, while three
stream sites exceeded the MOECC stream guideline of 0.03 mg/L. Zwicker Brook, Forties River, and
Sherbrooke River all exceeded the guideline by 0.01 mg/L, while Pine Lake Brook, Butler Lake Brook, and
Gully River were at the threshold (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 of the bimonthly
streams, it is reasonable to assume that the rainfall caused increased flushing of phosphorus into the
streams. As the monthly sampling for August did not occur until 10 days after the rainfall event, the
effects of the stream phosphorus flushing on lake sites would be minimal.
23 | Page
Figure 16: Total phosphorus at four monthly lake sites (Lake 1-4) during the May-October 2018 SL water quality field season.
Red line indicates the MOECC 0.02 mg/L guideline for phosphorus in lakes.
Figure 17: 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).
Red line indicates the MOECC 0.03 mg/L guideline for phosphorus in streams.
0
0.01
0.02
0.03
0.04
0.05
Total Phosphorus (mg/L)Lake 1 Lake 2 Lake 3 Lake 4
0
0.01
0.02
0.03
0.04
0.05
Total Phosphorus (mg/L)Sherbrooke River Forties River Pine Lake Brook Zwicker Brook
Butler Lake Brook Gully River Peter Veinot Brook
24 | Page
Phosphorus concentrations during the 2018 field season differ at several sites compared to the 2017
preliminary data (Table 3). Phosphorus concentrations are similar for all lake sites, while all stream sites
have increased phosphorus concentrations. The difference between the stream concentrations may be
due to the weather differences during sampling events, as the 2017 samples were collected on a day
without rain, while the 2018 samples collected during the same month (August) were collected during
the rainfall-dependent event.
Table 3: Range in total phosphorus concentrations between 2017 and 2018; July-August for lake samples, August for river
samples.
Site 2017 Range 2018 Range
Lake 1 0.005-0.008 0.004-0.008
Lake 2 0.004-0.005 0.004-0.009
Lake 3 No data 0.004-0.005
Lake 4 No data 0.004-0.007
Sherbrooke River 0.007 0.04
Forties River 0.016 0.04
Pine Lake Brook 0.019 0.03
Zwicker Brook 0.024 0.04
Butler Lake Brook 0.013 0.03
Gully River 0.01 0.03
Peter Veinot Brook 0.01 0.02
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 not significantly lower
than surface concentrations (Table 4). Phosphorus at-depth was 0.001 mg/L lower than Lake 1 surface
waters, while Lake 2 saw an increase of 0.021 mg/L between surface and at-depth concentrations. High
phosphorus concentrations in the deeper lake waters suggests that the thermocline is not allowing
nutrient mixing within the lake profile, and that there is minimal assimilation of phosphorus at-depth.
Although no algal bloom occurred during fall turnover in SL, caution should be advised to residents of SL
during the fall, as the mixing of elevated phosphorus concentrations increases the risk of a fall algal
bloom in the future.
Table 4: Total phosphorus concentrations from two lake sites, obtained both at the surface and below the thermocline, in August
for the SL 2018 Water Quality Monitoring Program.
Site Surface Phosphorus (mg/L) Phosphorus At-Depth (mg/L)
Lake 1 0.008 0.007
Lake 2 0.004 0.025
25 | Page
2.2.3. Total Nitrogen
Like phosphorus, nitrogen concentrations are also key and limiting nutrients 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 0.18 mg/L to 0.359 mg/L, while stream nitrogen
concentrations ranged from 0.35 mg/L to 0.883 mg/L (Figures 18 and 19, Table 5). Total nitrogen, just as
total phosphorus, was lower in lake sites than stream sites, and total nitrogen increased at all stream
sites compared to the 2017 preliminary sampling data – possibly due to a difference in sampling event
types. 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 once – 0.359 mg/L on July 31st, 2018.
Exceedance of the oligotrophic threshold, in addition to the elevated nitrogen concentrations at all
seven streams during the rainfall event suggests that nitrogen pollution may be a problem in SL in the
future, and that rainfall may be a key driver of how pollutants enter the lake. Of the bimonthly streams
monitored during the sampling program, all four streams had increases in total nitrogen during the
rainfall-dependent sampling. Of the lake sites sampled during the monthly August event, nitrogen
concentrations only increased at Lake 2, while Lake 1 and 3 dropped from the July concentrations – as
sampling occurred 10 days after the rainfall-dependent sampling, it is possible that the influx of nitrogen
from the inlet streams had been assimilated by plants, and therefore the lake’s elevated nitrogen
concentrations associated with the rainfall event may have been missed.
Figure 18: Total nitrogen at four monthly lake sites (Lake 1-4) during the May-October 2018 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
Total Nitrogen (mg/L)Lake 1 Lake 2 Lake 3 Lake 4
26 | Page
Figure 19: 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). Red
line indicates the Dodds and Welch (2000) 0.9 mg/L nitrogen threshold for freshwaters.
Table 5: Range in total nitrogen concentrations between 2017 and 2018; July-August for lake samples, August for river samples.
Site 2017 Range 2018 Range
Lake 1 0.258-0.36 0.185-0.359
Lake 2 0.234-0.324 0.18-0.258
Lake 3 No data 0.19-0.29
Lake 4 No data 0.189-0.196
Sherbrooke River 0.511 0.714
Forties River 0.685 0.751
Pine Lake Brook 0.629 0.781
Zwicker Brook 0.592 0.711
Butler Lake Brook 0.434 0.883
Gully River 0.441 0.483
Peter Veinot Brook 0.374 0.66
Just as with phosphorus, elevated nitrogen concentrations below the thermocline may indicate a
possible nutrient-enrichment event during fall turnover, with a potential for eutrophication and algal
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
Total Nitrogen (mg/L)Sherbrooke River Forties River Pine Lake Brook Zwicker Brook
Butler Lake Brook Gully River Peter Veinot Brook
27 | Page
blooms. In SL, nitrogen concentrations at-depth were not significantly lower than surface concentrations
(Table 6). Lake 2 had almost double the surface nitrogen concentration in the waters below the
thermocline. With elevated phosphorus and nitrogen concentrations below the thermocline, SL fall
turnover is essential for nutrient dispersal – and a concern for eutrophication. Although no algal bloom
occurred in fall 2018 in SL, caution should be taken in the future, especially at Lake 2 where nutrients
are particularly high.
Table 6: Total nitrogen concentrations from two lake sites, obtained both at the surface and below the thermocline, in August
for the SL 2018 Water Quality Monitoring Program.
Site Surface Nitrogen (mg/L) Nitrogen At-Depth (mg/L)
Lake 1 0.263 0.223
Lake 2 0.258 0.46
2.2.4. 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).
No hydrocarbons were detectable at any lake sites during either the preliminary-2017 and full-2018 SL
Water Quality Monitoring Program. Hydrocarbons should continue to be monitored at all lake sites to
monitor for changes in detectable amounts of hydrocarbons – especially at sites Lake 3 and 4, where a
public boat launch is proposed, which would see an increase in boat traffic, and by association, increases
in the potential for hydrocarbon releases into the lake. As hydrocarbons commonly form particulate
complexes that settle out of solution, collecting sediment hydrocarbon samples at sites Lake 3 and 4
may also be useful in developing a reference point prior to the installment of the SL public access site.
2.2.5. 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 (Figure 20). Chlorophyll a decreased over the 2018 sampling season and plateaued
from August to October. The highest chlorophyll a concentration was observed at Lake 1 in May 2018,
while Lake 3 consistently had the lowest chlorophyll a concentrations. The low chlorophyll a
concentrations throughout the 2018 field season, and no increase in chlorophyll a during the fall
turnover, coincide with the lack of algal blooms observed within the lake.
28 | Page
Figure 20: Chlorophyll a at four monthly lake sites (Lake 1-4), and two summer-only sites (Chl 1 and Chl 2) during the May-
October 2018 SL water quality field season.
2.2.6. Fecal Coliform Bacteria
Fecal coliform bacteria 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), 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
fecal coliforms measured in coliform forming units per 100 mL (CFU/100mL) as an indicator of fecal
pollution. Fecal coliforms act as a proxy for Escherichia coli (E. coli), Health Canada’s indicator bacteria
for fecal contamination in freshwaters, under the assumption that 90% of fecal coliforms are E. coli. For
recreational waters, Health Canada has set a limit of < 400 CFU/100 mL of fecal coliforms and 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 fecal coliforms indicates the presence of fecal contamination, the absence of
fecal coliforms 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 2018 field season, no site
exceeded the Health Canada primary contact limit (Figures 21 and 22). The highest fecal coliform count
0
1
2
3
4
5
6
7
8
9
10
Chlorophyll A (ug/L)Lake 1 Lake 2 Lake 3 Lake 4 Chl 1 Chl 2
29 | Page
within the lake sites was 20 CFU/100 mL, found at Lake 2 in July 2018. Samples were below laboratory
detection limits for all eight Lake 1 samples, six of seven Lake 2 samples, six of seven Lake 3 samples,
and two of three Lake 4 samples. For the streams, concentrations ranged from <10 CFU/100 mL to 350
CFU/100 mL. The highest bacteria concentration was recorded at Butler Lake Brook (350 CFU/100 mL),
during the rainfall-dependent event.
Elevated stream bacteria concentrations were recorded during both the August rainfall-dependent
event and September bimonthly event – these elevated concentrations may be due to flushing of
bacteria on land into the streams, as both samples coincided with heavy rainfall. 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 affect lake water quality. Although the rainfall-dependent sampling did not include sampling lake
sites, the September sampling event coincided with heavy rainfall and required both lake and bimonthly
sampling of the four primary inlet streams. Though the four streams had elevated September bacteria
concentrations, no increase in bacteria concentrations was recorded at any lake site. 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.
Figure 21: Fecal coliform at four monthly lake sites (Lake 1-4) during the May-October 2018 SL water quality field season. Red
line indicates Health Canada’s fecal coliform concentration limit for recreation in freshwaters (400 CFU/100 mL).
0
50
100
150
200
250
300
350
400
Fecal Coliform (CFU/100 mL)Lake 1 Lake 2 Lake 3 Lake 4
30 | Page
Figure 22: Fecal coliform 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 Health Canada’s fecal coliform concentration limit for recreation in freshwaters (400 CFU/100 mL).
2.3. Sediment Sampling
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
0
50
100
150
200
250
300
350
400
Fecal Coliform (CFU/100 mL)Sherbrooke River Forties River Pine Lake Brook
Zwicker Brook Butler Lake Brook Gully River
Peter Veinot Brook
31 | Page
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 Forties River site, may negatively
affect aquatic life (Table 7). Within the Lake 2 and 3 sites, arsenic, cadmium, lead, and mercury exceed
the CCME interim sediment quality guidelines (ISQG). In addition, manganese and selenium
concentrations appear to be close to CCME sediment guidelines and should be monitored (CCME, 2001).
Lake 2 has more exceedances of metal guidelines than Lake 3 – this may be due to the increased depth
and greater slope of Lake 2. 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.
Sediment metal concentrations at both SL lake sites 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 2 are greater than the mean metal concentrations found at Kejimkujik for
arsenic, cadmium, lead, manganese, and mercury (Table 8). In addition, the concentration of cadmium
in sediment at Lake 2 and 3 is greater than the maximum cadmium concentration found in the four
Kejimkujik lakes. Although Lake 1 sediment was not sampled during the 2018 monitoring program, it is
recommended that sediment sampling be done at the site in the future, due to the high metal
concentrations recorded at the Lake 2 and 3 sites.
As Forties River 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 sediments may also just be the
accumulation over time from metal inputs from other inlet streams. Expanding sediment analyses to
slowly assess sediment quality from the other six main inlet streams would help determine whether one
or multiple streams are influencing lake sediments accumulation quantities.
32 | Page
Table 7: Concentration of metals within site sediment samples sampled on August 27th, 2018. 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.
Sediment Sample Concentrations Concentration
Guidelines
Metal UNITS Lake 2 Lake 3 Forties
River RDL* ISQG PEL NSEQS
Acid Extractable Aluminum (Al) mg/kg 22000 6700 4300 10 - - -
Acid Extractable Antimony (Sb) mg/kg ND* ND ND 2.0 - - -
Acid Extractable Arsenic (As) mg/kg 16 8.3 2.7 2.0 5.9 17 17
Acid Extractable Barium (Ba) mg/kg 42 26 26 5.0 - - -
Acid Extractable Beryllium (Be) mg/kg ND ND ND 2.0 - - -
Acid Extractable Bismuth (Bi) mg/kg ND ND ND 2.0 - - -
Acid Extractable Boron (B) mg/kg ND ND ND 50 - - -
Acid Extractable Cadmium (Cd) mg/kg 1.0 1.5 ND 0.30 0.6 3.5 3.5
Acid Extractable Chromium (Cr) mg/kg 14 4.6 4.7 2.0 37.3 90 90
Acid Extractable Cobalt (Co) mg/kg 8.8 6.8 2.3 1.0 - - -
Acid Extractable Copper (Cu) mg/kg 15 13 ND 2.0 35.7 197 197
Acid Extractable Iron (Fe) mg/kg 14000 10000 8300 50 - - 47,766
Acid Extractable Lead (Pb) mg/kg 49 13 3.3 0.50 35 91.3 91.3
Acid Extractable Lithium (Li) mg/kg 10 11 20 2.0 - - -
Acid Extractable Manganese
(Mn) mg/kg 480 1000 200 2.0 - - 1,100
Acid Extractable Mercury (Hg) mg/kg 0.27 0.16 ND 0.10 0.17 0.486 0.486
Acid Extractable Molybdenum
(Mo) mg/kg ND ND ND 2.0 - - -
Acid Extractable Nickel (Ni) mg/kg 7.5 5.7 2.3 2.0 - - 75
Acid Extractable Phosphorus (P) mg/kg 1900 400 180 100 - - -
Acid Extractable Rubidium (Rb) mg/kg 6.3 4.7 17 2.0 - - -
Acid Extractable Selenium (Se) mg/kg 1.8 ND ND 1.0 - - 2
Acid Extractable Silver (Ag) mg/kg ND ND ND 0.50 - - 1
Acid Extractable Strontium (Sr) mg/kg 13 ND ND 5.0 - - -
Acid Extractable Thallium (Tl) mg/kg 0.26 0.34 0.12 0.10 - - -
Acid Extractable Tin (Sn) mg/kg 3.0 2.0 ND 2.0 - - -
Acid Extractable Uranium (U) mg/kg 5.7 1.7 0.52 0.10 - - -
Acid Extractable Vanadium (V) mg/kg 30 11 11 2.0 - - -
Acid Extractable Zinc (Zn) mg/kg 93 96 20 5.0 123 315 315
Orthophosphate (P) mg/kg 0.067 0.26 0.33 0.050 - - -
*RDL = Reportable Detection Limit; ND = Not Detected
33 | Page
Table 8: Comparison of 2018 sediment metal concentrations from SL Lake 2, Lake 3, and Forties River 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 2 Lake 3 Forties River Kejimkujik
Range
Kejimkujik Mean
Concentration
Acid Extractable Arsenic (As) mg/kg 16 8.3 2.7 3.55-27.1 10.50
Acid Extractable Cadmium (Cd) mg/kg 1.0 1.5 ND* 0.1-0.4 0.26
Acid Extractable Lead (Pb) mg/kg 49 13 3.3 43-62.5 48.40
Acid Extractable Manganese
(Mn) mg/kg 480 1000 200 28.7-666 273.40
Acid Extractable Mercury (Hg) mg/kg 0.27 0.16 ND 0.14-0.345 0.22
Acid Extractable Selenium (Se) mg/kg 1.8 ND ND 1.39-3.17 2.24
*RDL = Reportable Detection Limit; ND = Not Detected
Regarding the phosphorus levels within the lake and river sediment (Table 9), although Lake 2 has the
highest amount of phosphorus in sediment, Forties River has the highest orthophosphate to phosphorus
ratio. All three 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. 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 3 and Forties River are below the Ontario guidelines, suggesting minimal influence by pollution and
no negative effects on aquatic organisms; however, Lake 2 is close to the 2000 mg/kg severe effect level
(1900 mg/kg at Lake 2) and therefore may indicate pollution affecting the lake, and a potential for
internal loading for phosphorus in the lake causing algal blooms. Lake 2 should be considered a ‘site of
concern’ and be continued to be monitored due to high potential for nutrient-enrichment,
eutrophication, and algal blooms.
Table 9: Phosphorus concentrations in sediment samples from lake and river sites sampled on August 27th, 2018.
Lake 2 Lake 3 Forties River
Orthophosphate in sediment (mg/kg) 0.0067 0.26 0.33
Acid extractable phosphorus in sediment (mg/kg) 1900 400 180
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
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.
34 | Page
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 and Lake 2, therefore a TSI was created for both sites
(Table 10; Figure 23). Both sites indicate mainly mesotrophic conditions, with phosphorus
concentrations towards oligotrophic status. Concern should be minimal for the Secchi disk/water
transparency eutrophic-approaching 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). For 2018, the SL trophic status should be
considered borderline oligotrophic-mesotrophic.
Table 10: Carlson (1977) 2018 SL TSI scores and trophic states for total phosphorus, chlorophyll A, and Secchi disk for Lake 1
(red) and Lake 2 (blue).
TSI Score Trophic State Phosphorus Chlorophyll A Secchi Disk
< 40 Oligotrophic 33.3 28.6
40-50 Mesotrophic 42.3 40.7 48.6 47.38
> 50 Eutrophic
Figure 23: Carlson TSI for lakes, with TSI ranks for SL Lake 1 (red star) and Lake 2 (blue star). Transparency determined using
Secchi disk depth. From Carlson (1977).
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3.2. Algal Blooms
An algal bloom is the rapid increase and accumulation of microscopic plankton algae (phytoplankton) in
water bodies and can be detrimental of 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.
For SL, algal blooms have been reported in previous years; however, no bloom was sampled and
confirmed during the 2018 field season. Chlorophyll a – a proxy for biomass and indicator of potential
blooms – remained low throughout the summer and did not spike after fall turnover when nutrients
increased. In addition, algal blooms can occur in pockets, and it is possible that a bloom did occur, but
not at the sampling sites. Although no algal bloom was detected in 2018, the literature suggests an
increase in both size and frequency of algae blooms in the future (Michalak et al., 2013), therefore SL
may still experience algae blooms in years to come.
3.3. Pollution
Based on the low nutrient and bacteria concentrations, lack of detectable hydrocarbons and algal
blooms, and an oligotrophic-mesotrophic state of the lake, pollution appears to be minimal within SL.
Rainfall appears to be the biggest threat to water quality within the lake – affecting the seven inlet
streams via bacteria and nutrient levels. Though no effect was observed within the lake during the
rainfall events, the continued input from these streams may influence long-term productivity of the
lake.
Heavy metals within the lake sediments suggests that some degree of pollution does exist within the
lake. 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
lead 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.
As the SL water quality is not heavily affected by human pollution – aside from long-term sediment
contamination - it is important to continue monitoring and highlighting changes in water quality within
the lake and its inlet streams, to ensure issues are identified and best management practices are
applied. In addition, as high metal concentrations have been found within SL sediment, sediment
analyses should also be included in long-term monitoring and management plans of SL.
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4. Recommendations
The following recommendations are suggested for the SL Water Quality Monitoring Program, based on
the 2018 water quality results:
● The SL Water Quality Monitoring Program should continue in 2019 and beyond, as construction
of the public access site - and expected 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 properties acquired by MODL for
public use.
o Sampling of the seven inlet streams should continue during rainfall-dependent events,
to determine how rainfall events are affecting inlet streams. Sampling of one lake site
during the rainfall-dependent event would also add information regarding how the
streams are influencing the lake during rainfall events.
o The program should consider purchasing a rainfall and water level gauge, to be set up
and monitored by volunteers, to provide volunteers greater decision-making tools when
trying to capture a rainfall-dependent sampling event.
● The Lake 4 site should be added to the 2019 water quality monitoring program, with a minimum
of hydrocarbons being sampled at the location.
● The addition of monitoring hydrocarbons in the sediment of sites Lake 3 and 4 should be
considered to track hydrocarbon loading at the lake bottom in areas with projected high traffic
and potential high contamination.
● The 2019 stream sediment sample should be obtained from a different inlet stream, to gather
more spatial information about nutrient and metal loading from the different streams
discharging into the lakes, especially to locate if one stream is contributing excess pollutants and
highly influencing lake sediment.
● Fecal bacteria testing should be switched from fecal coliforms to E. coli, as E. coli is Health
Canada’s primary indicator of fecal contamination.
● Monitoring of Chl 1 and Chl 2 sites should be ceased, as Lake 1 is close enough to both sites that
duplication of sampling should be avoided.
● Monitoring of Lake 1 bottom sediments should be undertaken to determine the levels of
phosphorus and metals in bottom sediments.
● Residents of SL should continue to be supplied with laboratory-certified bottles and sampling
procedures for the collection of water samples during an algae bloom.
o There should be emphasis in public education about the SL monitoring program, with
increased awareness of what blooms are, how they occur, what they look like, and
actions to take in the event of a bloom. Information should be shared with both
residents of the lake, and at the public access site for visitors of the lake.
o Caution should be advised to SL users during the fall, due to fall turnover and high
potential for an algal bloom – especially at the Lake 2 site.
37 | Page
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