HomeMy Public PortalAboutFox Point Lake Water Quality Monitoring Report 2016
Fox Point Lake
2016 Water Quality Monitoring Report
Prepared for
Municipality of the District of Chester
Water Quality Monitoring Committee (Mill Cove)
By
Bluenose Coastal Action Foundation
37 Tannery Road, PO Box 730
Lunenburg, N.S.
B0J 2C0
January 2017
Table of Contents
Page
1.0 Introduction
1.1 Project Background……………………………………………………………………………………………………….. 1
1.2 Review of 2015 Water Quality Report……………………………………………………………………………. 4
1.3 Changes to the 2016 Water Quality Monitoring Program………………………………………………. 4
2.0 Water Quality Monitoring Results
2.1 Algae Bloom…………………………………………………………………………………………………………………... 7
2.2 Trophic State………………………………………………………………………………………………………………….. 8
2.3 Thermal Stratification…………………………………………………………………………………………………….. 11
2.4 Water Temperature……………………………………………………………………………………………………….. 17
2.5 Dissolved Oxygen…………………………………………………………………………………………………………… 18
2.6 pH………………………………………………………………………………………………………………………………….. 20
2.7 Total Dissolved Solids…………………………………………………………………………………………………….. 22
2.8 Total Suspended Solids………………………………………………………………………………………………….. 23
2.9 Total Phosphorus…………………………………………………………………………………………………………… 24
2.10 Total Nitrogen……………………………………………………………………………………………………………… 26
2.11 Fecal Coliform……………………………………………………………………………………………………………… 28
2.12 Rainfall and Water Level……………………………………………………………………………………………… 30
2.13 Stream Discharge………………………………………………………………………………………………………… 30
3.0 Discussion………………………………………………………………………………………………………………………………….. 32
4.0 Recommendations……………………………………………………………………………………………………………………… 33
References……………………………………………………………………………………………………………………………………….. 35
Page
List of Figures
Figure 1. Fox Point Lake drainage basin and locations of four water quality monitoring sites………….. 3
Figure 2. Relocation of the North Inlet sample site at FPL in 2016……………………………………………………. 5
Figure 3. Location of second dissolved oxygen/water temperature profile site in FPL……………………… 6
Figure 4. TSI calculations for Fox Point Lake in 2016………………………………………………………………………… 10
Figure 5. Thermal stratification of a water column displaying three layers of varying densities………. 11
Figure 6. Thermal stratification in oligotrophic and eutrophic lakes represented by
Dissolved oxygen/water temperature depth profiles………………………………………………………….. 12
Figure 7. Common dissolved oxygen profiles found in thermally stratified lakes……………………………… 13
Figure 8. Dissolved oxygen/water temperature depth profiles at Lake Site 1 in 2016………………………. 15
Figure 9. Dissolved oxygen/water temperature depth profiles at Lake Site 2 in 2016………………………. 16
Figure 10. Water temperatures at five FPL sample sites from June to October, 2016………………………. 18
Figure 11. Dissolved oxygen at five FPL sample sites from June to October, 2016……………………………. 20
Figure 12. pH at five FPL sample sites from June to October, 2016………………………………………………….. 22
Figure 13. Total dissolved solids at five FPL sample sites from June to October, 2016……………………… 23
Figure 14. Total phosphorus at four FPL sample sites from June to October, 2016………………………….. 26
Figure 15. Total nitrogen at four FPL sample sites from June to October, 2016……………………………….. 28
Figure 16. Rainfall and water level results at FPL from June 22, 2016 to October 21, 2016……………… 30
Figure 17. Stream discharge rates in the outlet and inlet streams at FPL from June to
October, 2016…………………………………………………………………………………………………………………….. 31
List of Tables
Table 1. Locations of monitoring sites at FPL in 2016………………………………………………………………………… 6
Table 2. Mean and range values for key parameters from Lake Site 1 from June to
September, 2016………………………………………………………………………………………………………………….. 9
Table 3. Means and ranges of variables associated with trophic levels in lakes…………………………………. 9
Table 4. Comparison of Secchi disk, chlorophyll a, and total phosphorus TSI scores in
2015 and 2016 at Fox Point Lake………………………………………………………………………………………….. 10
Table 5. Mean and maximum summer water temperatures from July to September,
2016 and 2015 maximum summer water temperatures……………………………………………………….. 18
Page
Table 6. Mean and maximum summer dissolved oxygen results from July to September,
2016 with 2015 results for comparison……………………………………………………………………………… 19
Table 7. Mean and minimum pH results from June to October, 2016 with 2015
results for comparison………………………………………………………………………………………………………. 21
Table 8. Total suspended solids (mg/L) results at four FPL sample sites from June
to October, 2016………………………………………………………………………………………………………………. 24
Table 9. Mean and maximum total phosphorus results from June to October,
2016 with 2015 results for comparison…………………………………………………………………………….. 25
Table 10. Mean and maximum total nitrogen results from June to October,
2016 with 2015 results for comparison…………………………………………………………………………….. 27
Table 11. Fecal coliform (cfu/100 mL) results at four sample sites from June to
October, 2016…………………………………………………………………………………………………………………… 29
Table 12. Mean and range of stream discharge rates in FPL outlet and inlet streams
from June to October, 2016……………………………………………………………………………………………… 31
1
1.0 Introduction
1.1 Project Background
The Fox Point Lake Water Quality Monitoring Committee was appointed by the Municipality of
the District of Chester in November 2014, in response to ongoing concerns about the water
quality of Fox Point Lake (FPL) and the Aspotogan Ridge development project in Mill Cove.
Aspotogan Ridge will be a 550-acre family lifestyle community, with the construction of over
500 residential units and an 18-hole golf course planned over the next several years. Residents
of Fox Point Lake have documented several siltation run-off events in the lake during
construction of the golf course, leading to concerns over the impacts of the development
project on the health of Fox Point Lake and its drainage basin.
The Water Quality Monitoring Committee was tasked with developing a Water Quality
Monitoring Program to document the baseline water quality conditions of Fox Point Lake and
track any changes in the health of the lake over the course of the development project. In 2015,
Bluenose Coastal Action Foundation was contracted to develop this monitoring program,
provide training and assistance to a group of volunteers, and to analyze and report on the
water quality results of the initial monitoring period. A description of the monitoring program,
including the sampling methodology and field procedures, can be found in Fox Point Lake
Water Quality Monitoring Program (2015), and the results of the first monitoring season can be
found in Fox Point Lake Water Quality Monitoring Report (2015), available on request from the
Municipality of the District of Chester.
The goals and objectives of the monitoring program remain unchanged from those stated in
2015 and are as follows:
Program Goals:
1. Establish a baseline of the water quality conditions and trophic status of Fox Point Lake
based on an initial monitoring period of May-October 2015, with the understanding that
conditions may already be degraded to a certain degree as a result of development
activities.
2. Monitor the water quality conditions and trophic status of Fox Point Lake throughout the
course of the multi-year Aspotogan Ridge development project.
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Program Objectives:
a) Monitor various biological, chemical, and physical water quality parameters in Fox
Point Lake to establish a baseline of these indicators and track any changes as a result of
development.
b) Determine the current trophic status of Fox Point Lake based on results of the initial
monitoring period (May-October 2015), using the following key parameters: total
phosphorus, total nitrogen, chlorophyll a, and Secchi disk depths.
c) Monitor the trophic status of Fox Point Lake throughout the course of development for
signs of cultural eutrophication.
d) Monitor the water depth of Fox Point Lake throughout the course of development as
an indicator of sediment in-filling or altered drainage basin hydrology.
e) Monitor precipitation amounts throughout the course of development to track local
rainfall patterns and the severity of associated siltation events in Fox Point Lake.
f) Monitor stream flow discharge in two inlet streams and one outlet stream of Fox Point
Lake throughout the course of development as an indicator of altered hydrology within
the drainage basin.
g) Monitor and document siltation events and algal blooms occurring in Fox Point Lake
throughout the course of development.
h) Monitor thermal stratification of Fox Point Lake by conducting temperature/
dissolved oxygen profiles to track the influence of increased nutrient loading on the
algal and dissolved oxygen conditions of the lake.
Fox Point Lake is the largest lake on the Aspotogan Peninsula. This 1.4 km² lake is shallow, long,
and narrow, with 11 small islands and an average depth of 4.9 m (Beanlands, 1980). The lake
receives drainage from its 8 km² catchment area through two inlet streams. The northern inlet
flows through wetland habitat and drains the northern half of the catchment area, while the
southern inlet flows directly through the golf course development site and drains the southern
end of the catchment. A single outlet stream in the southeast corner of the lake flows directly
into St. Margaret’s Bay.
The FPL Water Quality Monitoring Program was designed to be carried out by residents of the
lake on a volunteer basis, with the assistance of the Coastal Action Project Manager throughout
the summer. In 2015, four sample sites were established around the lake, as well as a rainfall
and water level monitoring station on a volunteer’s shoreline property. Sample site locations
3
were chosen to monitor water quality conditions in the lake, the outlet stream, and the north
and south inlet streams before they enter the lake (see Fig. 1).
Figure 1 – Fox Point Lake drainage basin and locations of four water quality monitoring sites.
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1.2 Review of 2015 Water Quality Report
The 2015 monitoring season provided valuable baseline data on the overall health of Fox Point
Lake and its outlet and inlet streams. Following the initial monitoring period in 2015, it was
determined that Fox Point Lake is healthy but at risk of cultural eutrophication if anthropogenic
activities within its catchment area are not properly managed.
The trophic state was identified as oligotrophic approaching mesotrophic, meaning that the
lake has low to moderate biological productivity. Thermal stratification occurred in the lake
from June to October, leading to severe oxygen depletion in the bottom layer of the lake.
Surface water temperatures in the lake exceeded 20°C in July and August, which causes stress
for many aquatic organisms. These high surface water temperatures and low dissolved oxygen
conditions in the bottom layer of the lake indicate that the outlet and inlet streams are likely
providing important thermal refugia habitat for the fish populations of Fox Point Lake. The
North Inlet sample site displayed very low dissolved oxygen concentrations during the warmest
part of the summer. Nutrients (nitrogen and phosphorus) exceeded the recommended
guidelines at the South Inlet sample site on several occasions, indicating that this stream is
suffering from excessive nutrient loading. Fecal bacteria results fell well below Health Canada
guidelines established to protect human health, except for one occasion when guidelines were
exceeded at the North Inlet and South Inlet sample sites.
1.3 Changes to the 2016 Water Quality Monitoring Program
Two changes were made to the monitoring program in 2016, which involved the relocation of
the North Inlet sample site, and the addition of a second dissolved oxygen/water temperature
profile site in the lake.
The North Inlet sample site was moved approximately 100 m downstream from its original
location in 2015 (see Fig. 2). The construction of a beaver dam immediately downstream of the
original location caused a number of issues with accessing the site and collecting all the
required data throughout the 2015 monitoring period.
5
Figure 2 – Relocation of the North Inlet sample site at FPL in 2016.
In 2015, depth profiles for dissolved oxygen and water temperature were conducted on a bi-
weekly basis at the deepest point (19 m) in the lake (Lake sample site) to monitor thermal
stratification throughout the water column and dissolved oxygen conditions in the bottom layer
of the lake. These profiles revealed that Fox Point Lake was thermally stratified from June to
October and dissolved oxygen became severely depleted in the bottom layer of the water
column. In order to gain a better understanding of thermal stratification and oxygen depletion
in the lake, a second profile site was established at the northern end of the lake in another
deep spot (16 m) (see Fig. 3). The original Lake sample site will now be referred to as ‘Lake Site
1’ and the new depth profile site is called ‘Lake Site 2’. YSI and depth profile data are collected
from Lake Site 2; however, water samples for laboratory analysis are not collected from this
site.
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Figure 3 – Location of second dissolved oxygen/water temperature profile site in FPL.
Table 1 – Locations of monitoring sites at FPL in 2016.
Monitoring Site Site Coordinates
North Inlet N 44°36’55.14” W 64°05’24.21”
South Inlet N 44°35’47.00” W 64°04’60.00”
Lake Site 1 N 44°36’04.86” W 64°04.56.28”
Outlet N 44°35’52.92” W 64°04.31.99”
Lake Site 2 N 44°36’29.14” W 64°05’15.06”
Rainfall/Staff Gauges N 44°35’56.62” W 64°05’02.11”
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2.0 Water Quality Monitoring Results
The following section provides an analysis of the 2016 monitoring program results. Many of the
water quality parameters will be compared to established guidelines that have been designated
by the Canadian Council of Ministers of the Environment (CCME), Health Canada, or through
other research bodies.
According to residents of FPL, no siltation run-off events were observed during the summer
months of 2016 and the lake water was clearer than they have seen it over the past several
years. The Aspotogan Ridge development project, currently one of the most significant sources
of anthropogenic activities within the FPL catchment area, was not active during the 2016
monitoring period. Golf course operations and construction activities were put on hold and it is
currently unknown when this development project will recommence.
2.1 Algae Bloom
On June 22, 2016, an algae bloom occurred in Fox Point Lake. Members of the FPL volunteer
group collected a water sample to be analyzed at Maxxam Analytics laboratory for microcystin-
LR, which is a toxin produced by cyanobacteria (blue-green algae). Analysis of the water sample
indicated a level of microcystin-LR of 1.25 µg/L, confirming the presence of cyanobacterial
toxins in the bloom. The drinking water guideline for cyanobacterial toxins – microcystin-LR is
1.5 µg/L (Health Canada, 2010). This guideline is meant to protect against exposure to other
types of microcystins which may be present in a bloom. Microcystins can persist in aquatic
environments after a visible bloom has dissipated (Federal-Provincial-Territorial Committee on
Drinking Water, 2002).
Freshwater cyanobacteria can accumulate in surface waters, producing a ‘bloom’ or ‘scum’
layer on the surface of a waterbody. Cyanobacterial blooms can persist in water with adequate
supplies of nitrogen and phosphorus, water temperatures between 15-30°C, and a pH between
6.0 - 9.0 and tend to recur within the same waterbody year after year. There is no simple
method to distinguish between toxic and non-toxic blooms; therefore, every algal bloom should
be treated as potentially dangerous. In general, 50-75% of the isolates from a bloom are
capable of producing toxins and there is often more than one type of toxin present, although
not all cyanobacterial blooms will produce toxins. Exposure to cyanobacterial toxins is most
often through the consumption of drinking water, and minor exposure can occur through
recreational activities and other domestic water uses. Although rare, illnesses can occur from
recreational exposure through skin contact or inadvertent ingestion of water, and can include
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stomach cramps, vomiting, fever, headache, eye and skin irritation, and muscle pain and
weakness (WHO, 2003; Federal-Provincial-Territorial Committee on Drinking Water, 2002).
The analysis of microcystin-LR in the water sample from FPL was sent to a laboratory in Alberta
and results were not received by the Coastal Action Project Manager for several weeks. As a
precaution, all algae blooms in FPL should be treated with caution as soon as they occur rather
than wait for confirmation on the presence of cyanobacterial toxins. Domestic water use should
be restricted and recreational use of the lake by humans and pets should be avoided until after
the bloom has dissipated.
2.2 Trophic State
The trophic state of a lake describes its level of biological productivity and provides a valuable
benchmark from which to monitor changes in the health of a lake and its drainage basin as a
result of various anthropogenic activities. Oligotrophic lakes display low levels of productivity
and relatively pristine conditions, mesotrophic lakes have moderate biological production, and
eutrophic lakes exhibit high productivity and high densities of plant biomass. Eutrophication is
the natural, long-term process of lakes progressing from lower trophic states to higher ones,
while cultural eutrophication refers to the accelerated trend towards higher trophic states due
to anthropogenic impacts within the drainage basin of a lake. Symptoms of cultural
eutrophication include excessive nutrient loading, increased algal and rooted aquatic plant
growth, and low dissolved oxygen conditions (Brown & Simpson, 1998; Brylinsky, 2004).
Determining the trophic state of a lake involves the analysis of key variables: total phosphorus,
total nitrogen, chlorophyll a, and Secchi disk depth. In 2015, these water quality parameters
were used to assess the trophic state of Fox Point Lake by calculating the Carlson Trophic State
Index (TSI) scores (Carlson, 1977). The trophic state of Fox Point Lake in 2015 was determined
to be oligotrophic and approaching mesotrophic. This analysis has been repeated using results
from the 2016 monitoring season to identify any changes in trophic state.
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Table 2 – Mean and range values for key parameters from Lake Site 1 from June to October,
2016.
Total Phosphorus
(µg/L)
Total Nitrogen
(µg/L)
Chlorophyll a
(µg/L)
Secchi Disk Depth
(m)
Mean 6.8 214 3.05 2.69
Range 5 - 8 187 - 266 1.25- 5.21 1.72 – 3.26
Table 3 – Means and ranges of variables associated with trophic levels in lakes (Brown &
Simpson, 1998).
A comparison of the results from Lake Site 1 (see Table 2) to a set of ranges and means
established by Vollenweider & Kerekes (1982) (see Table 3) suggests that the trophic state of
Fox Point Lake is predominantly oligotrophic and approaching mesotrophic. Additional analysis
of trophic state, using the Carlson Trophic State Index (TSI), will provide a numerical score for
each key parameter which can be directly compared to the scores calculated in 2015. The TSI
ranges from 0 to 100 and can be calculated for each parameter individually using the following
formulas:
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Secchi disk: TSI(SD) = 60 – 14.41 ln(SD) TSI(SD) = 45.7
Chlorophyll a: TSI(CHL) = 9.81 ln(CHL) + 30.6 TSI(CHL) = 41.5
Total phosphorus: TSI(TP) = 14.42 ln(TP) + 4.15 TSI(TP) = 31.8
(ln = natural log)
Figure 4 – TSI calculations for Fox Point Lake in 2016.
Table 4 – Comparison of Secchi disk, chlorophyll a, and total phosphorus TSI scores in 2015 and
2016 at Fox Point Lake.
2015 2016
TSI (SD) 49 45.7
TSI (CHL) 34 41.5
TSI (TP) 37 31.8
Lakes with a TSI of less than 40 are oligotrophic, mesotrophic lakes have TSI values between 40
and 50, and lakes with a TSI value greater than 50 are classified as eutrophic. The TSI value for
chlorophyll a is often given priority as it provides the most accurate prediction of algal biomass.
TSI scores indicate, again, that Fox Point Lake has a trophic state of oligotrophic, approaching
mesotrophic, meaning that the lake has low to moderate biological productivity.
The decrease in TSI scores for Secchi disk depth from 49 in 2015 to 45.7 in 2016 reflect
improved water clarity. The average Secchi disk depth, in 2016, was 2.69 m at Lake Site 1 and
2.92 m at Lake Site 2, compared to an average Secchi disk depth of 2.09 at Lake Site 1 in 2015.
Residents of the lake have reported that the water clarity is better than they have seen in years.
The increase in TSI scores for chlorophyll a indicate an increase in algal biomass; however,
Secchi disk depth is not only influenced by algal biomass, but can be effected by the presence of
sediment, silt, and other materials in the water column (NSSA, 2014; EPA 2002).
This analysis of trophic state has not identified any significant changes in the biological
productivity of the lake from 2015 to 2016. The trophic state of oligotrophic approaching
mesotrophic remains the same as 2015, even with slight changes in TSI scores. Two years of
monitoring data have produced a valuable baseline of trophic conditions in FPL from which to
assess changes in future monitoring years.
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2.3 Thermal Stratification
Thermal stratification of a lake involves the separation of the water column into layers of
different densities based on changing water temperatures (see Fig. 5). This process begins with
spring turnover, when the water temperature of a lake is consistent from top to bottom. Wind
circulation draws dissolved oxygen from the surface to the bottom waters and pulls nutrients
from the bottom to the surface. In late spring/early summer, the surface waters begin to warm
and three layers begin to form throughout the water column. The epilimnion represents the
warmer surface layer, where light can penetrate and wind action circulates the water, adding
dissolved oxygen. The metalimnion, or thermocline, represents the middle layer where
temperature changes rapidly with depth. The bottom layer, or hypolimnion, holds the coldest,
densest water.
Figure 5 – Thermal stratification of a water column displaying three layers of varying densities
(Chowdhury et al., 2014).
By late summer, when stratification is at its strongest, there is little to no mixing between the
layers, which means that the hypolimnion is no longer receiving dissolved oxygen from the
surface. This finite supply of dissolved oxygen in the bottom layer can be depleted over the
course of the summer because of organic material sinking to the lake bottom and being
decomposed by bacteria. The available dissolved oxygen is consumed through microbial
decomposition, leading to extremely low dissolved oxygen levels in the hypolimnion and a
decreased ability to support aquatic life (Brylinsky, 2004).
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Low dissolved oxygen conditions have significant physiological and behavioural effects on
aquatic organisms. The CCME Guideline for the Protection of Aquatic Life for dissolved oxygen
is ≥ 6.5 mg/L for cold-water species and ≥ 5.5 mg/L for warm-water species (CCME, 1999).
Dissolved oxygen levels which fall below this guideline cause stress in aquatic organisms and
may result in relocation, dormancy, or death.
Thermal stratification is broken in autumn as surface waters cool and the water temperature
becomes uniform from top to bottom once again. Once the density layers have broken down,
mixing of the water column replenishes dissolved oxygen in the bottom waters (see Fig. 6).
Figure 6 – Thermal stratification in oligotrophic and eutrophic lakes represented by dissolved
oxygen/water temperature depth profiles (Wetzel, 2001).
There are four types of dissolved oxygen profiles that can develop during thermal stratification,
depending on the level of biological productivity (trophic state) of a lake (see Fig. 7). An
orthograde profile is seen in oligotrophic lakes (low nutrient input, low productivity) when the
dissolved oxygen concentration decreases in the epilimnion and increases in the hypolimnion.
Clinograde profiles are observed in eutrophic and mesotrophic lakes (high nutrient input, high
productivity) when the dissolved oxygen concentration decreases in the hypolimnion and
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increases in the epilimnion. Heterograde profiles develop when there are high or low
concentrations of dissolved oxygen at unlikely depths throughout the water column. Negative
heterograde profiles display low dissolved oxygen concentrations in the metalimnion
(thermocline), usually caused by an accumulation of decomposing organisms caught at the
density boundary. Positive heterograde profiles display high dissolved oxygen concentrations in
the metalimnion, usually caused by a high concentration of photosynthesizers in that part of
the water column (Mackie, 2004).
Figure 7 – Common dissolved oxygen profiles found in thermally stratified lakes (Mackie, 2004).
Depth profiles were conducted at both Lake Site 1 and Lake Site 2 from June to October, 2016
(see Fig. 8 and Fig. 9). At Lake Site 1, thermal stratification was established by June 15 with a
thermocline depth of 8 m and dissolved oxygen concentrations above the CCME guideline
throughout the water column. In July, the thermocline shifted upwards to approximately 4-6 m
depth, which increased the proportion of the hypolimnion layer in the water column. Depth
profiles on August 11 and August 23 displayed negative heterograde profiles, which means that
decomposing organisms were caught in the density boundary of the thermocline (metalimnion)
and consuming oxygen. By August 23, dissolved oxygen concentrations had fallen below the
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CCME guideline. Depth profiles in September displayed clinograde profiles and dissolved
oxygen concentrations had dropped as low as 2.74 mg/L. By October 27, thermal stratification
had broken down at Lake Site 1 and water temperatures and dissolved oxygen concentrations
were uniform throughout the water column.
At Lake Site 2, thermal stratification was established by June 15 with a thermocline depth of 8
m and dissolved oxygen conditions just above the CCME guideline. In July, the thermocline
shifted upwards to a depth of 4-6 m, which increased the proportion of the hypolimnion layer.
Depth profiles in July and August displayed clinograde profile curves, which indicates high
productivity and microbial decomposition in the hypolimnion. On September 9, dissolved
oxygen still displayed a clinograde profile, with concentrations dropping as low as 2.89 mg/L.
Thermal stratification was broken by September 30, with uniform water temperatures
throughout the water column and dissolved oxygen concentrations above the CCME guideline.
Thermal stratification was established at both Lake Site 1 and Lake Site 2 by June 15; however,
this stratification began to break down earlier at Lake Site 2. Both sites displayed clinograde
profiles and dissolved oxygen concentrations below 3 mg/L by late summer. Once established,
thermal stratification in FPL does not appear to break down at any point through the summer,
meaning that dissolved oxygen does not get replenished until fall turnover. Microbial
decomposition consumes most of this finite supply of oxygen, causing severe depletion in the
bottom waters of the lake.
If biological productivity increases in Fox Point Lake, oxygen conditions in the hypolimnion may
become hypoxic (< 2 mg/L) or anoxic (< 1 mg/L) (USGS, 2014), which causes a shift in microbial
decomposition from aerobic bacteria to anaerobic bacteria, which decompose organic material
20 times slower and release methane and hydrogen sulfide gases that are toxic to aquatic
organisms. Anoxic conditions can also lead to the release of phosphorus and metals from
bottom sediments through oxidation reduction reactions (Hayes et al., 1985). Bottom
sediments of Fox Point Lake may be holding a significant amount of phosphorus, given the
number of severe run-off siltation events that have occurred in recent years. If the bottom of
the lake becomes anoxic, internal phosphorus loading could lead to algal blooms and increased
aquatic plant growth in the lake (Brylinsky, 2004).
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Figure 8 – Dissolved oxygen/water temperature depth profiles at Lake Site 1 in 2016.
16
Figure 9 – Dissolved oxygen/water temperature depth profiles at Lake Site 2 in 2016.
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2.4 Water Temperature
Water temperature is one of the most important indicators of water quality which plays a
significant role in the health and productivity of aquatic ecosystems. Water temperature effects
many physical, chemical, and biological factors in an aquatic system. Dissolved oxygen is
strongly influenced by temperature, as cold water can hold more oxygen than warm water.
Aquatic organisms have varying levels of sensitivity to temperature as well as optimal
temperature ranges, and extreme temperature fluctuations outside of those optimal ranges,
both acute and chronic, can cause physiological stress, relocation, or death (NSSA, 2014).
Salmonids, such as Atlantic salmon (Salmo salar) and brook trout (Salvelinus fontinalis), require
cold water for survival. Brook trout, known to populate Fox Point Lake, are one of the most
temperature-sensitive salmonid species, and will begin to experience physiological stress if
water temperatures exceed 20°C. In response to high temperatures, fish will seek out areas of
thermal refugia, such as spring/groundwater-fed streams and streams with deep cold-water
pools (MacMillan et al., 2005).
Water temperature was monitored at all 5 sample sites on a bi-weekly basis from June to
October, 2016. Surface water temperatures were nearly identical at Lake Site 1 and Lake Site 2
(see Fig. 10), with both sites, as well as the Outlet site, exceeding 20°C from July to early
September. The South Inlet site displayed the lowest water temperatures, as much of this
stream flows through dense forest habitat which provides shade for the stream and maintains
cooler water temperatures.
Maximum recorded water temperatures increased from 2015 at the North Inlet, South Inlet,
and Outlet sites, while there was a decrease in the maximum temperature recorded at Lake Site
1 (see Table 5). Similar to what was observed in 2015, the inlet and outlet streams may be
providing important thermal refugia habitat for cold-water fish populations, such as brook
trout, as surface water temperatures exceed 20°C and dissolved oxygen levels decrease in the
bottom layers of the lake.
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Table 5 – Mean and maximum summer water temperatures from July to September, 2016 and
2015 maximum summer water temperatures.
North Inlet South Inlet Lake Site 1 Outlet Lake Site 2
Mean Summer Water Temperature (°C) 18.4 16.3 21.3 20.5 21.5
Maximum Summer Water Temperature (°C) 20.7 18.7 23 23.2 23.3
2015 Maximum Summer Water
Temperature (°C)
18.7 17.7 23.9 22.9 N/A
Figure 10 – Water temperatures at five FPL sample sites from June to October, 2016.
2.5 Dissolved Oxygen
Dissolved oxygen (DO) is one of the most important indicators of water quality and aquatic
ecosystem health. Sources of DO in water include wind and wave action, photosynthesis by
aquatic vegetation, rainfall, and cascading water. The amount of DO available to aquatic life in a
lake is influenced by several factors including thermal stratification, algal and aquatic plant
density, water temperature, and the oxygen content of inlet streams (EPA, 2002). The CCME
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Water Quality Guideline for the Protection of Aquatic Life for dissolved oxygen is ≥ 6.5 mg/L for
cold-water species and ≥ 5.5 mg/L for warm-water species (CCME, 1999).
Dissolved oxygen shows an inverse relationship with water temperature, with DO
concentrations decreasing at all sites during the warmest part of the monitoring period,
because oxygen becomes less soluble in water as temperature increases (CCME, 1999). Both
Lake Site 1 and Lake Site 2 display surface DO concentrations above the CCME guideline for the
entire monitoring period, due to wind and wave action and photosynthesis in the photic zone.
The North Inlet and South Inlet sample sites display DO conditions below the CCME guideline
from July to September. Both streams have very slow moving water, which limits the rate of
oxygen transfer from the atmosphere into surface waters. DO concentrations at the Outlet
sample site fell below the CCME guideline on three occasions; however, the cascading riffle
habitat upstream of this site normally maintains suitable DO conditions (see Fig. 11).
Table 6 – Mean and minimum summer dissolved oxygen results from July to September, 2016
with 2015 results for comparison.
North Inlet South Inlet Lake Site 1 Outlet Lake Site 2
Mean Summer Dissolved Oxygen (mg/L)
(2015 results)
3.36
(2.25)
5.63
(6.31)
8.02
(7.88)
6.97
(7.05)
8.09
(N/A)
Minimum Summer Dissolved Oxygen (mg/L)
(2015 results)
2.31
(1.38)
3.92
(5.86)
7.43
(7.33)
5.61
(5.75)
6.98
(N/A)
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Figure 11 – Dissolved oxygen at five FPL sample sites from June to October, 2016.
2.6 pH
pH is the measurement of the hydrogen-ion concentration in water, and is expressed on a
logarithmic scale from 0 to 14. A pH of 0 is the most acidic, a pH of 7 is neutral, and a pH of 14 is
the most basic. The CCME Guideline for the Protection of Aquatic Life is within the pH range of
6.5 – 9.0, while the drinking water guideline is 6.5 - 8.5, and the recreational water quality
guideline is 5.0 - 9.0 (CCME, 2002). Natural variation in pH occurs as a result of the composition
of soils and bedrock, drainage from coniferous forests, and the amount of aquatic vegetation
and organic material present. Anthropogenic influences on pH include wastewater discharge,
increased atmospheric carbon dioxide, and acid precipitation (B.C. MoE, 1998).
Fish and other aquatic organisms experience negative physiological impacts in acidic water with
pH < 5.0. Salmon can withstand a pH as low as 5.0, while trout are slightly hardier and can
withstand a pH as low as 4.7. The impact of low pH depends on the proportions of organic and
inorganic acids in the water. Organic acids, which leach out of soils and wetlands and give water
21
a tea color, are less harmful to aquatic life than inorganic acids (sulphuric and nitric acids) from
acid precipitation (NSSA, 2014).
Acidification of water bodies is a significant issue in Nova Scotia, with the province having lost
the greatest percentage of fish habitat, due to acid precipitation, in all of North America. Nova
Scotia lies directly downwind of the high emission polluting areas of central Canada and the
Midwestern United States. Southwestern Nova Scotia suffers significantly from acid
precipitation due to the poor buffering capacity of the soils in this region, which are unable to
neutralize the effects of the acids (NSSA, 2015).
All the pH readings fell below the CCME Guideline for the Protection of Aquatic Life at the
North Inlet, South Inlet, Outlet, and Lake Site 2, while Lake Site 1 had only two recorded pH
values above the guideline (see Fig. 12). The North Inlet site is the most acidic, and both this
site and the South Inlet site displayed pH < 5.0 on October 27, 2016. The average and minimum
pH values recorded in 2016 have all increased from 2015 (see Table 7).
Table 7 – Mean and minimum pH results from June to October, 2016 with 2015 results for
comparison.
North Inlet South Inlet Lake Site 1 Outlet Lake Site 2
Mean pH
(2015 results)
5.17
(4.56)
5.64
(5.08)
6.39
(6.11)
5.74
(5.45)
6.06
(N/A)
Minimum pH
(2015 results)
4.36
(3.88)
4.85
(4.10)
6.08
(5.66)
5.59
(5.04)
5.86
(N/A)
22
Figure 12 – pH at five FPL sample sites from June to October, 2016.
2.7 Total Dissolved Solids
Total dissolved solids (TDS) is a measure of the amount of dissolved materials in the water
column, such as calcium, magnesium, chloride, sodium, sulphate, nitrate, and bicarbonate.
Dissolved solids can come from natural sources in the environment as well as from sewage
effluent, urban and agricultural run-off, industrial wastewater, and road salts. High TDS will
influence the taste, color, and clarity of water, thus restricting its use as drinking water or for
irrigation (B.C. MoE, 1998; NSSA, 2014). There are no guidelines for the protection of aquatic
life in terms of dissolved solids; however, Health Canada has established a drinking water
guideline of ≤ 500 mg/L (Health Canada, 1991). The average TDS for pristine lakes in Nova
Scotia is 20 mg/L (Hinch & Underwood, 1985).
Fox Point Lake displayed an average TDS of 29.7 mg/L (at both Lake Site 1 and Lake Site 2) in
2016, compared to an average of 27.5 mg/L in 2015, which falls above the average for pristine
N.S. lakes but well below the Health Canada drinking water guideline. Lake Site 1, Lake Site 2,
23
and the Outlet site all displayed very similar TDS levels (see Fig. 13) ranging between 28.6-31.2
mg/L. The North Inlet site displayed the highest TDS concentrations in both 2015 and 2016.
Figure 13 – Total dissolved solids at five FPL sample sites from June to October, 2016.
2.8 Total Suspended Solids
Total suspended solids (TSS) is a measure of the solids suspended in a water column which do
not pass through a 45 µm glass fibre filter, such as silt, clay, plankton, microscopic organisms,
and fine organic and inorganic particles. TSS is one of the most visible indicators of water
quality, as it provides a measure of sedimentation and water clarity. Sources of suspended
solids include natural geological erosion, agriculture, forestry, construction, and wastewater
discharge. High TSS can cause an increase in surface water temperatures as particles in the
water column absorb solar radiation, and a decrease in dissolved oxygen as suspended particles
decrease light penetration and rates of photosynthesis. The average background concentration
24
in Nova Scotia lakes is 3.0 mg/L (Hinch & Underwood, 1985). The CCME Guideline for the
Protection of Aquatic Life is also dependent on background (baseline) levels of suspended
solids. When background levels are ≤ 100 mg/L, the maximum allowable increase is 10 mg/L
above the background level. When background levels are > 100 mg/L, the maximum allowable
increase is 10% of background levels (CCME, 2002).
Table 8 – Total suspended solids (mg/L) results at four FPL sample sites from June to October,
2016.
North Inlet South Inlet Lake Site 1 Outlet
15-June-2016 ND (RDL = 1.0) 1.8 1.4 1.4
21-July-2016 1.2 5.5 ND (RDL = 1.0) 1.4
23-August-2016 ND (RDL = 1.0) 1 1.2 1.2
30-September-2016 2.0 1.8 ND (RDL = 1.0) 2.4
27-October-2016 2.0 1.2 1.2 ND (RDL = 1.0)
ND = Not Detected
RDL = Reportable Detection Limit
TSS results from Lake Site 1 fall below the average background concentration of TSS in Nova
Scotia’s lakes (3.0 mg/L), as they did in 2015, indicating that suspended solids are not a
significant problem in Fox Point Lake and are likely not contributing to increased surface water
temperatures or decreased dissolved oxygen conditions (see Table 8). Residents of FPL have
stated that the water was clearer during the summer of 2016 than it has been for several years.
The highest concentration of TSS was 5.5 mg/L, which occurred at the South Inlet site on July
21, 2016.
2.9 Total Phosphorus
Total phosphorus is a measure of both inorganic and organic forms of phosphorus. Phosphorus
is an essential nutrient for plant growth, and has few natural sources in the environment. It is
usually the limiting factor for the growth of algae and aquatic plants in freshwater systems,
meaning that elevated levels in a waterbody are likely a result of anthropogenic activities.
Natural sources of phosphorus in the environment come from weathering and erosion of rocks,
and the decomposition of organic matter. Anthropogenic sources of phosphorus include
25
industrial effluent, fertilizers, sewage effluent, and run-off from urban, agricultural, or forestry
land-use (B.C. MoE, 1998).
Lakes which are not significantly impacted by anthropogenic activities usually display total
phosphorus levels < 0.01 mg/L (B.C. MoE, 1998). CCME has not established a guideline for total
phosphorus because it is not a ‘toxic substance’, rather it has secondary effects such as
eutrophication and oxygen depletion (CCME, 2004). Provincial guidelines have been established
in some parts of Canada, but not in Nova Scotia. Guidelines established by Ontario’s Ministry of
Environment and Climate Change (MOECC) are widely cited and include separate guidelines for
lake and stream habitats. The total phosphorus guideline in lakes is ≤ 0.02 mg/L, and for rivers
and streams the guideline is ≤ 0.03 mg/L (MOECC, 1979).
Table 9 – Mean and maximum total phosphorus results from June to October, 2016 with 2015
results for comparison.
North Inlet South Inlet Lake Site 1 Outlet
Mean Total Phosphorus (mg/L)
(2015 results)
0.018
(0.020)
0.149
(0.164)
0.007
(0.010)
0.012
(0.008)
Maximum Total Phosphorus (mg/L)
(2015 results)
0.031
(0.030)
0.320
(0.240)
0.008
(0.014)
0.027
(0.008)
26
Figure 14 – Total phosphorus at four FPL sample sites from June to October, 2016.
Total phosphorus concentrations at Lake Site 1 remained below the MOECC guideline for lakes
(≤ 0.02 mg/L) for the entire monitoring period. The Outlet sample site did not exceed the
MOECC guideline for stream habitats (≤0.03 mg/L) and the North Inlet site narrowly exceeded
this guideline by 0.001 mg/L on one occasion. The South Inlet site exceeded the stream
guideline throughout the entire monitoring period, reaching a maximum total phosphorus
concentration of 0.32 mg/L on July 21, 2016 (see Fig. 14).
Total phosphorus results in 2016 are similar to those in 2015, with the South Inlet sample site
exceeding guidelines for the entire monitoring period. The average total phosphorus
concentration at the South Inlet sample site has decreased from 0.164 mg/L in 2015 to 0.149
mg/L in 2016 (see Table 9).
2.10 Total Nitrogen
Total nitrogen is a measure of all forms of organic and inorganic nitrogen. Nitrogen is an
essential nutrient in plant growth, and is usually the limiting factor for the growth of algae and
27
aquatic plants in marine systems. Anthropogenic sources of nitrogen include sewage effluent,
urban and agricultural run-off, and industrial effluent (B.C. MoE, 1998). Similar to total
phosphorus, the CCME has not established a guideline for total nitrogen because it is not
considered a ‘toxic substance’ and its negative effects on the environment occur through
secondary effects (eutrophication and oxygen depletion) (CCME, 2004). Guidelines have been
established through extensive research on the fate of nutrients in freshwater systems. Dodds &
Welch (2000) have established a total nitrogen guideline of ≤ 0.9 mg/L for freshwater
environments in which excessive nutrient loading and eutrophication are likely to occur.
Table 10 - Mean and maximum total nitrogen results from June to October, 2016 with 2015
results for comparison.
North Inlet South Inlet Lake Site 1 Outlet
Mean Total Nitrogen (mg/L)
(2015 results)
0.481
(0.530)
0.612
(1.22)
0.214
(0.234)
0.236
(0.365)
Maximum Total Nitrogen (mg/L)
(2015 results)
0.584
(0.624)
0.763
(2.01)
0.266
(0.266)
0.298
(0.696)
28
Figure 15 – Total nitrogen at four FPL sample sites from June to October, 2016.
In 2015, the South Inlet was the only sample site to exceed the guideline for total nitrogen (see
Fig. 15). In 2016, there were no exceedances of the guideline and the average total nitrogen
concentrations decreased at all four sample sites. The South Inlet site displayed an average
concentration of 0.612 mg/L and a maximum concentration of 0.763 mg/L in 2016, compared
to an average of 1.221 mg/L and maximum of 2.01 mg/L in 2015 (see Table 10).
2.11 Fecal Coliform
Fecal coliform bacteria are found in the waste of warm-blooded animals and are used as an
indicator of fecal contamination in the environment. There are hundreds of types of disease-
causing bacteria, viruses, parasites and other harmful microorganisms, making it impractical to
test for all of them. Non-pathogenic fecal bacteria species, which are easier and more
affordable to test for, are used as ‘indicators’ of the possible presence of more harmful disease-
causing organisms. E. coli (Escherichia coli) is the most appropriate indicator of fecal
contamination in freshwater environments. Most fecal coliform bacteria are comprised of E.
29
coli and will be used as a proxy measurement for E. coli, to be compared to the Health Canada
guidelines for E. coli.
Health Canada has developed several comprehensive guidelines for the protection of human
health. Separate guidelines have been developed to protect human health during various forms
of water recreation:
Primary contact: Activities in which the whole body or the face and trunk are frequently immersed or the
face is frequently wetted by spray, and where it is likely that some water will be swallowed (e.g.,
swimming, surfing, waterskiing, whitewater canoeing/rafting/kayaking, windsurfing, subsurface diving).
Secondary contact: Activities in which only the limbs are regularly wetted and in which greater contact
(including swallowing water) is unusual (e.g., rowing, sailing, canoe touring, fishing).
(Health Canada, 2012)
Sources of fecal contamination include stormwater run-off, malfunctioning septic systems,
livestock, wildlife, domestic animals, and agricultural run-off. The abundance and persistence of
fecal bacteria in freshwater systems can be influenced by several factors, which means that
bacteria sampling results can be highly variable. Exposure to water which is contaminated with
fecal bacteria poses a significant risk to public health and can cause illnesses such as
gastroenteritis, hepatitis, and respiratory infections (B.C. MoE, 1998; Health Canada, 2012).
The Health Canada guideline for primary contact is ≤ 400 cfu/100 mL, and the secondary
contact guideline is ≤ 1000 cfu/100 mL. The results for all four FPL sample sites fell well below
both the primary and secondary contact guidelines (see Table 11).
Table 11 – Fecal coliform (cfu/100 mL) results at four FPL sample sites from June to October,
2016.
North Inlet South Inlet Lake Site 1 Outlet
15-June-2016 20 10 ND (RDL = 10) 10
21-July-2016 60 70 ND (RDL = 10) 10
23-August-2016 20 30 10 10
30-September-2016 20 50 ND (RDL = 10) 10
27-October-2016 ND (RDL = 10) ND (RDL = 10) ND (RDL = 10) ND (RDL = 10)
ND = Not Detected
RDL = Reportable Detection Limit
30
2.12 Rainfall and Water Level
Rainfall amount and the water level of Fox Point Lake were monitored daily from June 22 to
October 21, 2016 using a rainfall gauge and a staff gauge. This provides valuable baseline data
to gain insight into the natural variability of this lake and its catchment, as well as identify any
significant changes which may be attributable to anthropogenic activities such as land level
alterations, watercourse and wetland alterations, irrigation water usage, or vegetation removal
(Fisheries and Oceans Canada, 2006).
The total rainfall amount from June 22 to October 21, 2016 equalled 163 mm, compared to a
total rainfall amount of 318 mm over the same time period in 2015. The water level of the lake
fluctuated between 0.63 m – 0.78 m in 2016, similar to 2015 levels which fluctuated between
0.61 m – 0.80 m (see Fig. 16).
Figure 16 – Rainfall and water level results at FPL from June 22, 2016 to October 21, 2016.
2.13 Stream Discharge
Water velocity was monitored at the North Inlet, South Inlet, and Outlet sample sites on a bi-
weekly basis, along with water depths and stream widths, to determine stream discharge rates.
The discharge rate of a stream is a product of its velocity times the depth and width (cross-
31
sectional area) of the water flowing in that stream. Anthropogenic activities which effect the
hydrologic conditions in a catchment area may result in changes in stream discharge rates
(Meals & Dressing, 2008).
The average discharge rates in 2016 are lower than the average rates in 2015 for all three
stream sites. This may be a reflection of the different rainfall amounts recorded during the 2015
and 2016 monitoring periods (2015 = 318 mm; 2016 = 163 mm). The South Inlet stream displays
the lowest discharge rate and the least variability (see Fig. 17).
Table 12 – Mean and range of stream discharge rates in FPL outlet and inlet streams from June
to October, 2016.
North Inlet South Inlet Outlet
Mean Stream Discharge (m³/s)
(2015 results)
0.213
(0.428)
0.027
(0.036)
0.178
(0.235)
Range of Stream Discharge (m³/s)
(2015 results)
0.161 – 0.271
(0.202 – 0.701)
0.012 – 0.035
(0.021 – 0.058)
0.032 – 0.540
(0.052 – 0.749)
Figure 17 – Stream discharge rates in the outlet and inlet streams at FPL from June to October,
2016.
32
3.0 Discussion
Fox Point Lake did not experience any siltation run-off events during the 2016 monitoring
season, and residents of the lake have stated that the water clarity was better than they have
seen in several years. Total suspended solids results have increased slightly from 2015 results in
the lake; however, they continue to fall below the average TSS concentration in Nova Scotia
lakes, and Secchi disk depths (another measure of water clarity) have improved since 2015.
An algal bloom occurred in the lake on June 22, 2016. Water sample analysis confirmed the
presence of the cyanobacterial toxin microcystin-LR. The concentration of this toxin did not
exceed drinking water guidelines. Cyanobacterial blooms tend to recur in the same waterbody
year after year, and it is likely that an algal bloom occurred during the summer of 2015, as
reported by FPL residents (samples were not taken to confirm the presence of toxins) (WHO,
2003).
Surface water temperatures in the lake and the outlet stream exceeded 20°C from July to early
September, which causes stress for fish and other aquatic organisms. Water temperatures in
the North and South Inlet streams remained cooler throughout the summer, indicating that
these streams may be providing important thermal refugia for fish populations in the lake.
While surface water temperatures were high at the Outlet sample site, this stream does have
deep, cold-water pools as well as better dissolved oxygen conditions compared to the North
and South Inlet sample sites; therefore, the Outlet stream is likely providing important summer
habitat for fish as well. It is important to maintain the health of these inlet and outlet streams
so they can continue to support aquatic life and to prevent excessive nutrient loading and
sedimentation from entering the lake from these streams.
Similar to 2015 results, exceedances of nutrient (phosphorus and nitrogen) guidelines were
only observed at the South Inlet sample site. This site exceeded the guideline for total
phosphorus throughout the entire monitoring period, although the average concentration did
decrease slightly from 2015. Total nitrogen concentrations have also decreased in the South
Inlet, with two guideline exceedances occurring at this site in 2015 and no exceedances in 2016.
With few natural sources in the environment, it is likely that the excessive phosphorus loading
in this stream is due to anthropogenic activities (B.C. MoE, 1998). The poor water quality in this
stream warrants further investigation.
An analysis of trophic state has confirmed the results from 2015, indicating that Fox Point Lake
is oligotrophic and approaching mesotrophic, which means it has low to moderate biological
33
productivity. Increased biological productivity could shift the trophic state to mesotrophic;
highlighting the importance of managing anthropogenic activities within the drainage basin to
prevent cultural eutrophication.
Thermal stratification was monitored at two locations in the lake in 2016. The lake was
thermally stratified from June to October and both monitoring sites displayed severe dissolved
oxygen depletion in the bottom layer of the lake (hypolimnion), with oxygen concentrations
dropping to < 3 mg/L. If biological productivity increases in Fox Point Lake, oxygen conditions in
the hypolimnion may become hypoxic (< 2 mg/L) or anoxic (< 1 mg/L) (USGS, 2014), which
causes a shift in microbial decomposition from aerobic bacteria to anaerobic bacteria, which
decompose organic material 20 times slower and release gases that are toxic to aquatic
organisms. Anoxic conditions can also lead to the release of phosphorus and metals from
bottom sediments through oxidation reduction reactions (Hayes et al., 1985). Bottom
sediments of Fox Point Lake may be holding a significant amount of phosphorus, given the
number of run-off siltation events in recent years. If the bottom of the lake becomes anoxic,
internal phosphorus loading could lead to algal blooms and increased aquatic plant growth in
the lake (Brylinsky, 2004).
4.0 Recommendations
The monitoring program at Fox Point Lake should continue. If biological productivity increases
in the lake, due to excessive external or internal nutrient loading, the lake is at risk of increased
algal blooms, anoxic conditions, and a decrease in its ability to support aquatic life. The South
Inlet stream has exhibited poor water quality, it is a source of excessive nutrient loading for the
lake, and it is likely suffering from anthropogenic impacts.
Increase monitoring efforts in the South Inlet stream. A detailed stream assessment
should be conducted along the entire length of this stream to identify sources of habitat
degradation, pollution, and nutrient inputs. Pending the results of a stream health
assessment, a second sampling site may be recommended further upstream towards
the headwaters of this stream.
Residents of FPL should continue to visually monitor the lake for algal blooms.
Information on algal blooms, including how to identify a bloom and what precautions to
take during a bloom, should be distributed to all residents of the lake.
34
Members of the volunteer group should continue to be equipped with sampling
materials to collect water samples in the event of an algal bloom. Follow-up sampling
should occur after a bloom has dissipated to confirm that cyanobacterial toxins are gone
before normal activity resumes in the lake.
All current sampling sites should remain as part of the monitoring program. Monitoring
and sampling frequencies should not be changed, with grab samples being collected for
laboratory analysis at a minimum of 5-6 times throughout the monitoring period.
35
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