What Water Studies Can Teach us
By: Diana Van Vlymen, with contributions from Peter Healy and Daniel Sauvé
Water. It’s what we drink, what we enjoy living besides, and what we play in. But it’s widely taken for granted here in Canada, a country with 20% of the world’s supply of this precious resource. Lake Temagami has some of the cleanest water in Ontario, but the critical question is how clean? And how can we keep the water clean for the years and generations to come?
In order to have the ability to protect our water, we have to obtain a baseline of the current water quality and monitor changes over a number of years. That is where the Temagami Lakes Association comes in, and it was the main reason for hiring two university students for the summer. The summer’s environmental programs involved a number of different water initiatives. Two rounds of water testing were completed, one during the period of May 14-24, and the other between July 30 and August 9. Each round of sampling was designed to measure the amount of phosphorus in the water and a number of other important factors. These included turbidity, dissolved oxygen (DO), temperature, and even pH (in August). Specialized scientific equipment was used to collect data, including a Secchi disc for turbidity, a Van Dorn bottle for water sample collection, a digital pH meter, and a ProODO (optical DO) probe. 43 sites around the lake were tested, with at least one in all arms of the lake. Some of these were historical sites, and a few were new ones, such as the site at the town docks, and the site in Shiningwood Bay.
At each location, the Secchi disc was let into the water to make a turbidity measurement. The process followed is to let the disc drift down into the lake until it is invisible, and record that value. Then the disc is dropped a few centimetres more, and brought back towards the surface until visible again. This value is also recorded, and both values are averaged to give the Secchi depth. Turbidity measurements are one of the characteristics used to define eutrophic vs oligotrophic lakes. Eutrophic lakes are shallow and nutrient rich (such as phosphorus), sometimes with algal blooms on the surface, while Temagami is a classic example of an oligotrophic lake. During the month of May, the average Secchi depth recorded was 6.52 metres (21 feet). The summer’s average depth found was 7.9 m (26 feet), which may be a result of the pollen clearing or the unusually cool weather we had early in August.
The next important measurement made was a record of temperature and dissolved oxygen from the surface to within a metre of the lake bottom at each site. These are not the easiest measurements to make, with Temagami’s constant wind, especially considering the deepest point was 72 m (236 feet)! We persevered and were able to construct a graph of these data, showing how the average temperature and dissolved oxygen readings vary with depth. From this graph, it can be seen that the temperature and dissolved oxygen follow different trends in the spring and summer, which can be attributed to the impact of the thermocline. Particularly in July, the sharp decrease in temperature can be appreciated. This unique area of the lake has a significant impact on the dissolved oxygen levels, too. It is noticeable that the oxygen rises in the thermocline, then steadily decreases as the depth increases. The thermocline contains phytoplankton, tiny organisms (including diatoms and algae) that act like plants: they perform photosynthesis, releasing oxygen into their surroundings. By virtue of the lake’s stratification in the summer, this oxygen remains in the thermocline, accounting for the higher oxygen in that layer. On the other hand, the hypolimnion (below the thermocline) (slightly/greatly) decreases in oxygen content throughout the summer, from the time spring turnover occurs until the fall turnover. Temagami is great for cold-water fish, as the dissolved oxygen remains consistently high deep in the lake. It does not drop below the critical point of 5.0 mg/L, the limit of oxygen which pickerel and especially lake trout require to survive. I’m sure all the anglers on the lake appreciate that!
The final important factor of freshwater chemistry is phosphorus. You’ve probably already heard of phosphorus in the news, as cottagers become more conscious of the impact their actions have on fragile lake ecosystems. Phosphorus is the major limiting factor in the growth of plants, including phytoplankton. The delicate balance of phosphorus allows for life in aquatic food chains, while limiting the growth of algae so it doesn’t overrun the lake. When too much phosphorus is present, algae multiply rapidly, and excess plant material sinks to the bottom as they die. This requires more decomposers, which consume oxygen in extraordinary amounts as their work increases, endangering the rest of the ecosystem. Phosphorus is naturally occurring in freshwater ecosystems, but excesses of the nutrient are introduced to the lake from human sources, primarily soaps, graywater from sinks and showers, and fertilizer runoff. That is why it is important to use phosphate-free cleaning products, locate graywater outflows well away from shore, and to avoid fertilizers. If you intend to plant a garden, it may be a good idea to buy plants well-suited to the Temagami climate to avoid the need for fertilizer.
Phosphorus is generally present in aquatic ecosystems in very small amounts, reported in μg/L (μg are micrograms; 1 is 1/10 of a mg). We collected water samples in the Van Dorn bottle, which has a special mechanism to keep the suction cups on either end open on its way down into the lake. When the appropriate depth is reached, according to markings on its cord, a messenger weight is dropped, causing the mechanism holding the ends open to release, trapping water inside at exactly the right depth. This water was collected at two depths for each site – the Secchi depth and ¾ total depth – in duplicates, so the phosphorus content could be more accurately recorded. These samples were sent away to Trent University’s field lab in Dorset ON, where colorimetry was performed on the samples to assess the phosphorus content using a spectrophotometer. It was determined that the lake averages 4.2 μg/L at Secchi depth and 5.1 μg/L at ¾ total depth in May, while the July averages are 3.4 μg/L and 4.9 μg/L, respectively. It is important to note that phosphorus typically decreases over summer months, and this is proportional to algal growth[1], as algae takes up phosphorus during growth. These measurements are very good, even for a lake in Northern Ontario. To put this in perspective, algae becomes a persistent problem when phosphorus reaches levels of 20 μg/L[2], and lakes in Muskoka and Georgian Bay reach as high as 35 μg/L[3]! Temagami is in much better shape at this time, but as TLA President Andrew Healy has said on multiple occasions, let’s compare ourselves not to other lakes in Ontario, but instead to Temagami’s past. For that reason we monitor the lake water. For the same reason, the TLA works to protect the environment by selling phosphate-free soap products. This is why the TLA works in partnership with Municipal staff to incorporate the underlying principles of the Tenets for Temagami in all municipal planning documents. We believe the legacy we leave behind is important to those who follow us.
For more information or to find out how you can make a difference, please contact the TLA at 705-237-8927 or .
[1] http://water.epa.gov/type/lakes/kezar.cfm
[2]http://www.kenoradailyminerandnews.com/2012/07/24/do-it-yourselfers-need-to-be-aware-of-mnr-regulations-when-working-near-water
[3]http://www.ene.gov.on.ca/stdprodconsume/groups/lr/@ene/@local/@lakepartner/documents/nativedocs/stdprod_082417.pdf