Moira Lake 2025 Final Water Quality Report
May - October 2025 Summary
​
Between May and July 2025, volunteers with the Moira Lake Property Owners Association (MLPOA) monitored water quality at six sites across the lake. This work helps us better understand how conditions change throughout the season — and what those changes might mean for the lake’s long-term health.
​
What We Observed
The 2025 monitoring season provided the clearest picture yet of how Moira Lake changes through the year — from the clear, cool conditions of spring to a dense midsummer algal bloom and the recovery that followed in fall. Sampling across six permanent sites captured the lake’s full cycle and revealed both its resilience and its growing vulnerability.
-
Phosphorus remains the main driver of algal blooms. Levels exceeded the Provincial Water Quality Objective (0.02 mg/L) across all sites, peaking in July and August at five to ten times the target.
-
Hardwater chemistry (high calcium and magnesium) traps nutrients in the lake, slowing recovery and sustaining summer stress.
-
Oxygen and clarity rebounded in October, showing the lake’s ability to recover when conditions cool and mix.
-
Moira Lake ranked among the most nutrient-enriched lakes in Eastern Ontario, confirming it as a regional outlier that needs ongoing management attention.
Why It Matters
Moira Lake is not in crisis, but it is under increasing pressure. Nutrients and minerals build up year after year, fuelling predictable summer blooms and oxygen stress. Without action, these cycles will continue, gradually reducing water clarity, habitat quality, and recreational value.​​
2025 Summary Scorecard
What It Means
These patterns are consistent with the natural rhythm of a productive lake — but they also underscore how vulnerable Moira Lake is to nutrient input, sediment disturbance, and rising temperatures. If these trends repeat year after year, they could lead to long-term ecological shifts that are harder to reverse.
How You Can Help
​
-
Pump out and inspect your septic system regularly
-
Avoid fertilizer use near the lake
-
Maintain or restore natural shoreline vegetation
-
Report unusual algae blooms or fish behaviour
-
Stay informed through MLPOA reports and updates
Moira Lake remains a living, responsive system — one that can still recover if given relief. With continued monitoring, community action, and strong local partnerships, lasting improvement is within reach.
​
Want to Learn More?
Two documents are available for your further reading:
-
A brief summary of the full report ( 7 pages).
-
The full 2025 Water Quality Report includes benchmark scores, site-by-site results, detailed seasonal observations, and parameter definitions (27 page report plus Appendices, total 46 pages).