Blue-green algae warning for Sandy Lake (Bedford) underscores concerns about ongoing and proposed development around the headwaters 28Jun2022

The last time: Algal bloom at Sandy Lake Beach  on Aug 6, 2019 View Post 7Aug2019
Click on image for larger version

In an article posted yesterday in the Chronicle Herald, Sandy Lake is reported to be one of 5 lakes in HRM in which blue-green algae (BGA, also known as cyanobacteria) have been detected recently. From the article:

The province is warning that blue-green algae has been spotted in five Halifax-area lakes and another three throughout Nova Scotia.

“This year we haven’t had any reports of anyone becoming sick or any dogs being harmed by blue-green algae,” said Elizabeth Kennedy, the director of the water branch for Nova Scotia Environment and Climate Change

The province reported blue-green algae in:

Sandy Lake in Bedford
Stillwater Lake in Tantallon
Coon Pond, in Upper Tantallon
Stream inlet into Bissett Lake in at Colby Drive in Cole Harbour
Just outside of HRM, Shubenacadie Grand Lake and Fish Lake             near Enfield

The province reports such occurrences and provides general info about BGA at

A factsheet, “Blue-green algae in previous years“, cited on that page, lists confirmed BGA occurrences for the years 2009-2021. There has been a big jump in the number of lakes affected since 2018. Sandy Lake is recorded as a site of BGA occurrence in Aug 0f 2019.

I happened to be at Sandy Lake Beach Park on the morning of Aug 6, 2019, shortly after the beach area was inundated with an “unpleasant suspended, reddish, soapy material” and reported it. The bloom came up quickly, lasted only a few days and then dissipated quickly.

For details, View

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

I proposed an explanation for the sudden appearance and then disappearance of the algal bloom at Sandy Lake which relates to a precipitous drop in water level causing release of nutrients from deeper water. I have  suggested that  the bloom was an early warning signal of the precarious state of Sandy Lake;  that was also evident in data compiled by AECOM (2014) on phosphorus status of Sandy Lake. See: A DRAFT Report On the  State of Sandy Lake, the Historical Trends and its Future Trajectory (Feb 23, 2021)

This new occurrence  underscores concerns that development around the headwaters of Sandy Lake, both ongoing  (below Hammonds Plains Rd)  and a major proposed new development above Hammonds Plains Rd.,  will further exacerbate water quality of Sandy Lake. The result: ever more frequent closures to swimming and likely  the lake would become inhospitable for salmonids, including the salmon that the Sackville Rivers Association and supporters have worked so hard to bring back to the Sackville River watershed*.
*Sandy Lake is the largest or 2nd largest (depending on how they are aggregated) sub-watershed of the Sackville River Watershed; salmon have been observed in Sandy Lake  recently. See: A salmon jumped right out of the water in Sandy Lake!; and Salmon fry spotted in Sandy Lake watershed 3 May2022

Climate warming has strengthened BGA blooms. What this means in practice is that to prevent them, we need to be much more stringent in our water quality care than in the past to prevent these blooms. We need to ‘walk the lakes backwards’ as much as possible toward their more pristine states.

Sandy Lake represents an enviable situation where we still have the option of choosing the most effective way to prevent the predictable and largely inevitable deterioration of a treasured lake associated with increasing urbanization: to strongly limit as yet unapproved development in the watershed, especially close to the lake itself and to streams draining into the lake.

It is a choice we may want to apply to other lakes in HRM. Currently, the principal way we attempt to predict potential impacts of development on lake water quality is by modelling the impacts on lake total P but without consideration of impacts of climate warming or increased salt loading on lake total P and associated processes. Clearly that is inadequate.

In HRM, we have the historic database, the coverage of a wide range of lakes, a strong academic tradition and ongoing research related to water resources, HRM and community support and involvement in water monitoring and a renewed commitment to monitoring that could enable us to produce far better predictive models to aid in decision-making.

Even without further development, it is important to reduce existing inputs of sediment, nutrients, organics and salt as much as possible to counteract the increasing stresses associated with climate warming (e.g., longer periods of summer-fall stratification, reduced oxygen solubility and more favourable temperatures for algal blooms).

To maintain Sandy Lake as an invaluable community recreational area and as habitat for iconic species such as salmon and loons, the Water Quality Objective for Sandy Lake should be to “walk the lake backwards” as much as possible to an earlier, more pristine, oligotrophic state.

Sandy Lake, already suggested as one of the Priority Lakes for monitoring (AECOM, 2020) would make a fine case study of a lake in transition from a healthy lake to a highly deteriorated lake. Hopefully, it would prove to be a case study on how we can reverse the current trends and engage the community in that process.

– From Conclusion to the A DRAFT Report On the  State of Sandy Lake, the Historical Trends and its Future Trajectory (Feb 23, 2021)

– David P, June 28, 2022

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