Cyanobacteria Notes


Harmful Algae Blooms
Page on

A risk advisory is issued when an algae bloom is observed. Initial testing is done to confirm if there is cyanobacteria in the algae bloom and the type of cyanobacteria present, if any. Certain cyanobacteria are toxin producing and others are not.
If there is no risk for toxin production, the risk advisory will be lifted and no further testing is required.
If there is a risk for toxin production, the risk advisory remains in effect. Visual bloom monitoring will continue until blooms have disappeared and remain absent for 7 days. At that time, water samples will be tested for toxins. The risk advisory will be lifted if toxins are within safe limits. If the toxin levels are above safe limits, then the risk advisory will remain in effect until later test results reveal that they are within safe limits (below current guideline values).

In 2020:
Lake MicMac: Advisory July 4, 2020 lifted Sep 11,2020
Shubie Canal Pond: Advisory Aug 29, 2020 | Lifted Sep 4, 2020
Lake Banook: Extended Jul 9, 2020 Lifted Aug 14, 2020
In 2019:
Sandy Lake: Advisory Aug 9, 2019 | Lifted Aug 10, 2019: Following initial water testing, the municipality has confirmed there are no toxin-producing strains of cyanobacteria present in the water. Lake MicMac was the only other lake cited in 2019

2019 bloom on Sandy Lake
Sandy Lake inundated by unpleasant, suspended, reddish, soapy material Aug 6, 2019; and lake level falling quickly
Post Aug 7, 2019

Advisory issued for Sandy Lake due to possible blue-green algae bloom Aug 7, 2019
Post Aug 7, 2019

Water quality issue at Sandy Lake Bedford has subsided (Aug 9, 2019)
Post, Aug 9, 2019

Field guide to algae and other “scums” in ponds, lakes, streams and rivers
Miriam Steinitz Kannan and Nicole Lenca, Northern Kentucky University 2013

Cyanobacteria Presence in Four Lakes in the Halifax Regional Municipality (HRM), Nova Scotia
Betts, Rebecca A. Dalhousie University Graduate thesis 2018. “The major objective of this project is to assess the presence of cyanobacteria (organisms that can pose serious challenges for drinking water treatment systems), in Halifax water supplies using DNA typing to identify cyanobacteria species. Four lakes in the Halifax Regional Municipality (HRM), NS, were chosen due to their differing water chemistry. A total of 35 taxa of cyanobacteria and one taxa of unassigned bacteria were detected, of which, 15 genera of cyanobacteria were identified. Of those genera, 11 have been associated with cyanotoxins, which are harmful to humans and animals. Supplementary data showed that two of the four lakes had higher pH, alkalinity, TN, TP and turbidity means than the others, and had detectable cyanotoxins and algal blooms after periods of rain followed by long periods of warm, dry, relatively calm weather. This thesis will provide a foundation for future experiments into lake and cyanotoxin management.”Some extracts from lit review 1.3. FACTORS THAT INFLUENCE BLOOMS
1.3.1. Eutrophication
Eutrophication in lakes occurs when excessive amounts of nutrients, in particular nitrogen (N) and phosphorus (P), are added to the water system from sources such as fertilizer run off, manure, and sewage (Paerl et al, 2015, 2016; Schindler et al, 2016). Lakes where phosphorus is high in ratio to other nutrients such as carbon and nitrogen, tend to be more favourable environments for cyanobacteria growth (Schindler et al, 2016; Verhamme et al, 2016; Lin et al, 2017).1.3.2. Climate Change and Lake Recovery from Acidification Rising temperatures and longer seasons caused by climate change results in higher temperatures and prolonged thermal stratification within lakes, preferred growth conditions for cyanobacteria (Whitton and Potts, 2000; Pick, 2016). Drought conditions can also be beneficial to cyanobacteria if periods of intense rainfall occurred prior to the drought, which would affect nutrient flow into watersheds and prolong stratification in lakes (Paerl et al, 2016; Pick, 2016).Another factor influencing the rise in algal and cyanobacteria blooms could also lie in the process of lake recovery from acidification.In Nova Scotia, lakes are typically acidic due to naturally occurring organic acids and bedrock geology, whereby silica-based gneiss and granite are acid sensitive due to limited carbonate sources and low base cation concentrations (Jeffries et al, 2003b; Ginn et al, 2015). Lake pH has been further depressed by long-range transport of sulphate(SO42-) from industrial centers in northeastern United States, the Laurentian Great lakes Area and local oil refineries and power generating stations, as well as by natural acidification from organic anions (Ginn et al, 2015).According to studies performed during the 1990’s, there were no trends showing lake recovery from acidification in lakes in Nova Scotia (Jeffries et al, 2003a). However, according to Anderson et al (2017), several drinking water supplies in Nova Scotia have been showing signs of lake recovery in recent years.Lake recovery from acidification could potentially mean the return of fish populations to water bodies, and the increase of cyanobacteria activity, as the chemical and biological effects of acidification are decreased (Jeffries et al 2003a,b).1.4. ALGAL BLOOMS IN NOVA SCOTIA
As mentioned previously, lakes in Nova Scotia are typically acidic due to naturally occurring organic acids and bedrock geology (Jeffries et al, 2003b; Ginn et al, 2015). However, due to influencing factors like eutrophication from mink farms, climate change, and potential lake recovery from acidification, blooms, even toxic blooms caused by cyanobacteria, have not been unusual to the province within the last decade (Whitton and Potts, 2000; Taylor, 2009; Brylinsky, 2011; Pick, 2016; Anderson et al, 2017).Mattatall Lake, shared between Colchester County and Cumberland County has experienced algal blooms since 2005 (Mathieson, 2015; Campbell, 2016; Tetanish, 2016). It has also been reported that these blooms can persist into November or even January. However, in 2017, there was no bloom observed at Mattatall Lake (Sullivan, 2017). Locals observed that unlike in previous years, the lake was clear, vegetation had begun to grow on the bottom of the lake, and a species of frog had returned. Yarmouth County and Digby County have experienced algal blooms every year since 2007 (Province of Nova Scotia (PNS), 2007, 2016f; Wendland, 2011; Lavoie, 2014; Allen, 2016). Of note, blooms have been observed in Lake Fanning, Parr Lake, Ogden Lake and Lake Vaughan in Yarmouth County, and Porcupine Lake in Digby County.

Other areas of note include Inverness County, where Lake Ainslie has had algal blooms in 2009 and 2010, and both the Southwest Margaree River and Margaree River have exhibited blooms in 2009 (PNS, 2009a,b, 2010). Lochaber Lake, located in both Antigonish County and Guysborogh County, experienced an algal bloom in 2012 (Lochaber Community Development Association, 2012). In Kings County, Lumsden Pond in the Lumsden Pond Provincial Park in Wolfville was reported to have algal blooms in 2013 and 2016, while Lake Torment has experienced blooms since at least 2014 (PNS, 2013b, 2014, 2015, 2016b,d; Tetanish, 2016). In 2015, an algal bloom was reported in Sherbrooke Lake in Lunenburg County, and in 2016 an algal bloom was reported in Middle River in Pictou County (PNS, 2016e; Tetanish, 2016).

Algal blooms have even been reported in Halifax County, albeit only in recent years. Algal blooms were reported at Powder Mill Lake in Waverley in 2016, and in Oathill Lake in Dartmouth in 2017 (PNS, 2016c; Meloney, 2017). However, the bloom in Oathill Lake was determined to be a green algae bloom, and was not definitively associated with cyanobacteria.


Urban Lakes Management Planning
Presentation to Harbour East Marine Drive Community Council, October 4, 2018 by Oathill Lake Conservation Society

Ecosystem revival set back by unexpected algae bloom in Dartmouth lake
Nic Meloney · CBC News · Posted: Oct 09, 2017 “Conservation group has noticed irregular amount of green algae collecting on surface of Oathill Lake”

Community calls for fix to algal blooms, weeds and bacteria in Dartmouth lakes
By Taryn GrantStar Halifax Fri., Aug. 23, 2019

Dartmouth. Lakes Town Hall
Thursday, August 22nd, 2019 MicMac Amateur Aquati c Club, Dartmouth, Nova Scotia

Oathill Lake Restoration
Slideset Dec 19, 2014