By John Francis, Bruce Peninsula Press
A few weeks ago, Northern Bruce Peninsula’s Municipal Council received a delegation from residents and cottagers concerned about the 2024 algal bloom in Stokes Bay and the shoreline fouling and water quality problems it caused.
At its November 25, 2024 Meeting, Council received a delegation from Bruce Peninsula Biosphere Association (BPBA) in the person of retired Bruce Peninsula District School science teacher John Rodgers.
Rodgers is Vice Chair of BPBA and Board Lead on the Six Streams Project which studies water quality in six streams/rivers in the former Eastnor Township. The project measures the presence of pollutants and nutrients in five streams that flow through cropland and cattle pastures, including Stokes River; the sixth stream, Black Creek, drains only wilderness and acts as a control. The Biosphere Association has also been instrumental in getting cattle watering systems installed in a number of locations, which keeps the cattle out of the streams and dramatically reduces pollution. (Note that phosphorus and nitrogen are “nutrients” when they are on a field and “pollution” when they get into a river.)
Rodgers brought Council up to speed on the issues affecting Stokes Bay and the Stokes Bay River. He began by asking who had seen the TVO series All Too Clear. Deputy Mayor Rod Anderson responded with an enthusiastic yes.
FYI: All Too Clear is a three-part series about water quality in the great lakes. It was created by local filmmakers Yvonne Drebert and Zach Melnick. It can be found (FREE) online on YouTube or TVO (no commercials on TVO).
Rodgers explained that there are horsemen for this apocalypse. One of those horsemen is the introduced species which are having a profound effect on freshwater ecology: Zebra Mussels and Quagga Mussels. The mussel species are filter feeders; they filter all the organisms out of the water column and then excrete them onto the lake bottom.
To quote the researchers in Part II of All Too Clear: “In a week’s time, every gallon of water in Lake Michigan could have passed through a mussel. The nutrients that used to fuel the world’s largest freshwater ecosystem are now trapped in the lakebed, creating vast aquatic deserts.”
Another horseman is phosphorus. He likened it to hot dog buns — you get twelve wieners but only eight buns, so you always run out of buns first. In Lake Huron, phosphorus is like the buns — it is the limiting factor, the element in shortest supply. If you increase the supply of phosphorus, then you will get a bloom of algae, because all the other ingredients are there in abundance: warm water, carbon dioxide, sunlight. In fact, most of Lake Huron is phosphorus-deficient because of the introduced mussels. Zebra mussels are a shallow-water species; they have cleaned out all the phosphorus-containing organisms in the surface water. Quagga mussels are a deepwater species; they have cleaned out all the phosphorus-containing organisms in the rest of the water column.
But in the near-shore areas, other factors come into play and phosphorus can build up.
An embayment, such as Stokes Bay, will have reduced water exchange with the Lake, which allows phosphorus to build up if there is a source. The extreme clarity of the water — caused by mussels filtering out all the organisms that would reduce that clarity — means that sunlight can penetrate right to the bottom in shallow bays, which in turn allows filamentous algae (Cladophora) to grow rapidly, utilizing the nutrients secreted on the bottom by the mussels.
Another of the horsemen is climate change. Warmer temperatures accelerate the growth of the algae; reduced wind speeds result in less water exchange with the open lake (especially when the winds come out of the east), which further accelerates the process.
The end result is a foul-smelling, black, rotting mass of decaying algae on shore. Rodgers emphasized that this is the end result, but that the problem is elsewhere.
Several different processes are contributing to increased phosphorus levels in inshore areas.
Shoreline disturbances free up the phosphorus from soil, which then enter the bay as run-off.
Climate change figures here too, because more intense rainstorms cause flooding. When fields are flooded at the height of the growing season, plants are caught in their period of maximum growth. They drown quickly and release their phosphorus back into the floodwaters.
And then there is the emeral ash-borer, a pest which is devastating our ash forests. Rodgers explained that he has lost about 90% of the trees on his farm. Dead trees expose the soil beneath them, making more phosphorus available to be flooded away and carried downriver to Lake Huron.
Removal of plants along the lakeshore makes this worse. As Rodgers explained, “One of the things that plants are really good at is removing phosphorus from the water…”
The result of all of this is a perfect storm of algae…
The Biosphere Association is working on a number of fronts, including:
• improving drainage of fields (which in turn reduces flooding, thereby reducing the leaching of phosphorus),
• encouraging cover-cropping in fields, which reduces erosion and leaching,
• working to replace failing septic systems (which contribute both phosphorus and nitrogen),
• working with shoreline landowners to discourage shoreline hardening and encourage planting of native plant species along the shore.
John Rodgers’ presentation can be seen on MNBP’s YouTube channel; look for the November 25 Council Meeting, Part 2. The presentation begins around minute 4:00 and continues to about minute 17:00.
For All Too Clear, go to inspiredplanet.ca or TVO or YouTube.
