Residents around Moose Lake got a more in depth look at how their lake behaves basin-by-basin.
On Feb. 7, Bradley Peter of the Alberta Lake Management Society (ALMS) was at the Moose Lake Watershed Society (MLWS) AGM to present the findings of the 2016 LakeWatch Program. Typically, the lake has been studied as a one water body – with samples from different locations being averaged.
For the summer of 2016, the MLWS wanted to take a different approach.
“This is the first year we did the individual basin sampling. We've had the LakeWatch Program for 11 years now for the overall water quality of the lake, but people always said that they wanted to know more about the individual bays,” explained Kellie Nichiporik of the MLWS. “They know the lake behaves differently in the individual bays; they want a more conclusive look at what's happening in each of these bays.”
The study ran over the course of last summer, with sampling being done on three separate dates – June 16, July 27, and Sept. 21. It looked at Franchere Bay, the Main Basin (Bonnyville Beach), Pelican Narrows, and Vezeau Bay, as well as the Moose Lake as a whole.
While it's only the first year, with no past data to compare, the study confirmed what many had suspected.
“I wasn't really surprised by it… It was pretty much the general trend we were expecting, with Franchere Bay being more productive with a lot more nutrient loading and that's what we found out with the individual basin sampling.”
From the samples taken, the first testing measured phosphorus levels, which Peter noted is “generally accepted to be the main nutrient that drives algae blooms.”
When taking the average of the three testing dates, the nutrient was found to be highest in Franchere Bay at 55 micrograms/litre – significantly more than the next highest reading of 27 micrograms per litre in the Main Basin. The lowest phosphorus average was recorded in Vezeau Bay at 25 micrograms per litre.
“The bottom sediments in a lake are really rich in phosphorus. If you have good agriculture in the area, then you're probably going to have a productive lake because the same nutrient-rich sediments are in the bottom of the lake,” explained Peter, noting that other sources of phosphorus include fertilizer and bird waste.
“That's why Alberta is known for green lakes, because we have really phosphorus rich soils.”
The samples were also tested for chlorophyll-a, which is the green pigment in algae and acts as an indicator of how much algae is in the lake.
As with phosphorus, Franchere Bay was substantially higher than the others with 52 micrograms per litre. The next highest was just 19 micrograms per litre in the Main Basin, and Vezeau Bay was again recorded as having the lowest concentration with 15 micrograms per litre.
For chlorophyll-a Moose Lake falls into the hypereutrophic category, meaning its very productive, averaging 27 micrograms per litre for the whole lake.
Also relating to testing for algae is the presence of microcystins, the toxins that are produced by blue-green algae. It's this toxin that can cause severe liver damage if ingested and, if over Alberta's recreational guidelines of 20 micrograms per litre, will prompt a beach advisory.
While the microcystin concentrations remained relatively low, there was a large spike on July 27 in Franchere Bay measuring 20.74 micrograms per litre. This was around the same time a blue-green algae advisory was issued for Moose Lake by Alberta Health Services (AHS).
With Moose Lake moving into hypereutrophic status, Nichiporik said the concern is that there will be more frequent algae blooms on the lake. But, it's too soon to tell.
“This is the first year our lake is in the hypereutrophic stage. It's really hard to say what that means at this time, basing it on one year is not a good way to determine the health of the lake.”
She added that it is a natural progression for lakes to become increasingly productive as they age.
“That's why we want to do a nutrient study and get as much data as we can.”
The MLWS is already planning on conducting individual basin testing again this summer, and hopes to continue it for a third year in 2018. They recently completed a tributary sampling in 2014, and are now hoping for a nutrient study to round out their testing.
Nichiporik expressed having the information at hand will help the society “manage the lake a little better and improve water quality over time.”
