First of all, we’d like to acknowledge the work of the volunteers who take part in the lake water quality studies. Nothing said below is meant to imply that it’s not worthwhile to monitor the quality of water in our lakes. Even super-athletes need annual medical checkups.
The organization responsible for lake monitoring at Louisa is called the Lake Louisa Property Owners’ Association (LLPOA). The main scientific authority used by the LLPOA at their website is a group of publications called Natural Resources Facts, put out by the University of Rhode Island, College of Resource Development.
Here’s a link to the University of Rhode Island original article called Algae in Aquatic Ecosystems. Following are some quotes.
ALGAE ARE NORMAL & HEALTHY
“Algae are necessary and beneficial to aquatic eco-systems. They form the food and energy basis for nearly all other aquatic organisms. They are part of a healthy lake ecosystem … all lake organisms depend either directly or indirectly on algae as a food source.”
BLOOMS ARE NATURAL
“It is important to realize that algae occur in natural cycles of abundance in aquatic ecosystems. Algal populations are abundant in spring and early summer. As long as algae do not reach nuisance levels, they play an important, essential role in a healthy aquatic ecosystem.”
EXCESS PHOSPHOROUS CAUSES NUISANCE ALGAE
“The best way to limit algal growth is to limit the amount of nutrients that enter the lake …phosphorus is considered the limiting nutrient in most fresh water bodies.”
AUTUMN LEAVES ARE THE SINGLE BIGGEST SOURCE OF PHOSPHOROUS
Now we turn to other sources of science.
In a classic 1979 study in New Hampshire, published in Ecology Volume 60, Meyer & Likens found that 48% of total annual input of phosphorus happened during the 10 days associated with autumn leaf fall. (Transport and transformation of phosphorus in a forest stream ecosystem)
British online publication World of Water says that, “Falling leaves in large numbers could clog up ponds and cause a nutrient overload in autumn. This can lead to algal blooms in spring.”
The newest article is in the August 2013 issue of Cambridge University’s International Journal of Limnology, called Catchment Vegetation Can Trigger Lake Dystrophy Through Changes In Runoff Water Quality. It concludes that, “surface runoff from forest areas can significantly affect lake chemistry [and] dystrophication”.
In other words, contrary to popular opinion, the wild and wooly look of a forested shoreline can be exactly what hastens the decline of our treasured lakes.
Here’s what nobody tells you. Roots are tiny foragers. They scrounge around underground collecting the chemicals plants need to grow. Some of these chemicals get transformed into wood and the rest become leaves. Before winter, our trees go dormant and the leaves fall off as waste. Each dead leaf is a concentrated chunk of fertilizer. As far as the lake is concerned, these colourful tidbits aren’t much different than manure (OMG).
We’re not going to denude our forests (and that would cause even worse problems), but there’s nothing wrong with our established lawns running down close to the lake. Grassy strips provide good buffer zones against nutrient overload from Autumn leaves and other forest detritus. If you have a lawn, don’t fertilize, use a mulching mower, be proud of the way you’re helping the lake – and hope for sensible municipal regulation.
To prevent erosion at the edge of the lake, the best solution is to plant (or let grow) some shrubs and bushes along the first metre or two. If the bushes grow too high or wide, they can be safely pruned in November when they’re dormant in preparation for Winter. Here again are the pictures that the Ontario Ministry of Natural Resources provides as examples of “best practices”.