HomeMy Public PortalAbout2019_Report Card_Sherbrooke Lake_Water QualityCoastal Action l 45 School Street, Suite 403 l Mahone Bay, Nova Scotia l B0J 2E0 l phone (902) 634-9977 l www.coastalaction.org
Sherbrooke Lake STEWARDSHIP
Water quality monitoring at Sherbrooke Lake is led by the Sherbrooke
Lake Stewardship Committee (SLSC). SLSC is comprised of citizen
representatives appointed by the Municipality of Chester and the
Municipality of the District of Lunenburg, in addition to a water
quality expert, and officials from both municipalities. SLSC receives
technical support from Coastal Action, who have also led the LaHave
River Watershed Project since 2007. Both municipalities provide
funding to support the SLSC, while trained volunteer lake residents
conduct the monthly sampling from May to October. 2019 marked
the second year of comprehensive monitoring at the lake.
Sherbrooke Lake Sampling
Water samples are collected from lake and inlet stream sites and
analyzed for total suspended solids, total nitrogen, total phosphorus,
E. coli, hydrocarbons, and chlorophyll a. Four inlet streams are
monitored bimonthly, while seven streams are sampled after a large
rainfall to monitor water quality changes related to high volumes of
runoff. Bottom sediment samples are collected from three lake sites
and one river site to assess the long-term accumulation of nutrients
and metals, which can influence the lake’s water chemistry.
how is sherbrooke lake's water quality?
Bacteria
All lake sites were consistently below Health Canada’s recreational
guideline for E. coli (400 CFU/100 mL). This guideline was exceeded
only once at a stream site on Forties River, on September 9, 2019.
This exceedance, along with bacteria concentration spikes at other
stream sites, was associated with a large rainfall event during
Hurricane Dorian. Elevated bacteria levels after rainfall are common
and were observed during the 2018 season as well. Lake and stream
water should always be treated prior to consumption (i.e., bathing,
washing, drinking).
Algal Blooms
Several algal blooms were reported in June and July of 2019 at
Sherbrooke Lake, covering vast areas of the lake. Algal bloom
samples were collected twice and neither sample had detectable
levels of microcystins – the toxin associated with cyanobacteria
(sometimes referred to as blue-green algae). An assessment of
the algal species present in these samples determined that non-
harmful green algae were the dominant species. Blooms are caused
by a complex interaction of biological, chemical, atmospheric, and
hydrographic conditions; many of which are uncontrollable. However,
excessive nutrient inputs are one of the most influential factors in
promoting a bloom and one of the most controllable.
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Figure 1: 2019 map of Sherbrooke sampling sites.
sherbrooke lake 2019 Water Quality Report Card
Nutrients
For much of the sampling season, nitrogen and
phosphorus concentrations fell within their respective
guidelines for freshwater streams and lakes; however,
both nutrients spiked following the Hurricane Dorian
rainfall event due to overland runoff, which transports
nutrients from roads, lawns, gardens, and agricultural
lands into the water. While nutrient concentrations
in the water column remain low, concentrations
sampled from bottom sediment were higher. This
indicates a level of nutrient pollution entering the lake
and settling to the bottom. In low oxygen conditions,
these nutrients may become resuspended causing
internal nutrient loading in the lake. Nutrient inputs
from human activities should be minimized as much as
possible to protect the lake from eutrophication and
algal blooms.
Overall Lake Health
Sherbrooke Lake is generally healthy but vulnerable.
Human activities such as fertilizing, removing shoreline
vegetation, and poor septic system maintenance can
all impact the lake’s water quality.
Coastal Action l 45 School Street, Suite 403 l Mahone Bay, Nova Scotia l B0J 2E0 l phone (902) 634-9977 l www.coastalaction.org
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Algal blooms are a natural part of lake ecology but can be enhanced in size and frequency if pollution sources add extra
nutrients into the environment. In a balanced ecosystem, algae and other organisms’ growth is limited by the amount of
nutrients available; however, if nutrients become available in excess (both naturally through fall and spring turnover and
sediment resuspension, or through human-caused pollution), algal blooms can occur. Not all plumes are algae (i.e., pine
tree pollen forms a film on the water’s surface), and not all algae are toxic; however, only a water test can confirm the
presence/absence of toxic algae species. Algal blooms should be reported to the Nova Scotia Environment Office in
Bridgewater (902-543-4685).
Did you know?
Take Charge of your Environment!
Limit your footprint with these at-home tips:
Vegetated Buffers
Leave a section of natural vegetation between any lawns and
the lake to filter runoff.
Pick Up Pet Waste
Put pet waste in its place: the garbage bin.
Fenced Livestock
Keep livestock out of the water with fences (provide livestock
with alternate sources of drinking water).
Manure Liners
Line manure piles to prevent bacteria and nutrients from
leaching into adjacent waterways.
Straight Pipes
Replace illegal straight pipes with septic systems and
keep your systems properly maintained.
Fertilizing before rain
Avoid fertilizing your lawn before a storm, as excess
nutrients will be washed into nearby waterways.
Dish soaps with phosphate
Avoid using dish soaps with phosphates, especially at
the cottage, as the nutrients can cause harmful algal
blooms in the water.
Try this Avoid this
Coastal Action is a charitable organization on the south shore of Nova Scotia that believes in
safeguarding a healthy environment for future generations. For over 25 years, our goal has been
to promote the restoration and conservation of our environment through research, education, and
action. We work in four core areas: Watersheds & Water Quality, Species at Risk & Biodiversity,
Climate Change & Education, and Coastal & Marine.
1: A weather station was placed at Sherbrooke Lake to help monitor rainfall in the area. Data
from the station is open to the public. 2: Trained volunteers collecting water samples from
Sherbrooke Lake during the 2019 field season.
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