Sat. Mar 2nd, 2024
Children's playgrounds on lake lands

Today’s post comes from Emily Wright, discovery leader at Grundy Lake Provincial Park. The park’s campground is surrounded by three crystal-clear lakes, and that rich biodiversity inspired Emily to take us on a water tour of Ontario’s lakes and some of the complex life cycles they contain, from the hardworking microbe-cleaning crews to the small fighters. -lower mouth.

Cannonballing into a refreshing lake, casting a line in hopes of finding the “big one,” dipping your paddle into serene waters, or simply enjoying the changing lights dancing across the surface of the water on a sunny day…

Lakes offer us a great deal of fun, both invigorating as you swim at a brisk pace, and calm and relaxing as you watch a sunset change the waters from blue-green to wine red.

Not only are the lakes beautiful, but fresh, clean water is essential to our daily lives! Lakes are reservoirs of rain and groundwater and, along with wetlands, are responsible for collecting, filtering and cleaning the same water we drink, bathe and cook with.

Therefore, our lives are fundamentally intertwined with these pockets of fresh water. The health of our lakes directly reflects our own health, and yet we rarely glimpse the complex and intricate systems that keep them clean, healthy, and enjoyable for everyone.

Let’s dive beneath these calm waters, descend through the various layers of life and discover how a giant “puddle” is able to feed, clean and sustain such a wide variety of wildlife… and us!

Green forests: the critical role of aquatic plants and life in the coastal zone

We’ll start near the surface of the water, along the shorelines, where sunlight gently filters in, flickering among the aquatic plants.


This “coastal zone” is where plants flourish. Here they have plenty of sunlight to give them energy, while still remaining rooted in the ground. Plants are the integral foundation of a lake and perform many important functions in keeping the waters clean and healthy.

100% organic water filter

Plants function as filters, absorbing excess nutrients and storing them in their stems, leaves and roots. Some are even capable of extracting small amounts of toxic hydrocarbon compounds or man-made chemicals such as fungicides, pesticides and antibiotics.

Others can bind to heavy metals such as mercury, boron, uranium and arsenic. It has been shown that the simple duckweed can absorb compounds such as lead, cadmium and even petroleum products to some extent!

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Water lily in the middle of aquatic flora

While plants in today’s ecosystems cannot completely remove the amount of pollutants currently entering natural systems (especially since many native aquatic plants are being eliminated by well-intentioned landowners or outcompeted by invasive species), they can work. hard and in fact they do it. to make waters safer for swimming, fishing and drinking.

Buffer zones

Plants serve as coastal barriers. Their complex root systems retain dirt.

person paddling a canoe

It produces and leaves slow waves, protecting coastlines from extensive erosion. This also improves water clarity, as the slowing of waves allows debris and dirt to settle to the bottom.

Power source

Almost all of a lake’s energy comes from plants (along with algae) that convert sunlight into oxygen and sugars. The plants are eaten by snails, insects, and other invertebrates, which are then eaten by small fish, which then feed large fish, and maybe even a loon or osprey! Or maybe you!

Largemouth bass and aquatic grass

Without the conversion of sunlight into energy by plants, the rest of the ecosystem would quickly collapse.


Coastal plants also provide the perfect nursery for fry (baby fish)!

Plant stems and leaves provide places for small fish to hide from predators, and large fish are rarely found in shallow water.


Small bass, pike, sunfish and many others hatch from their nests and nestle among the fluttering leaves. Here they feed on smaller creatures, such as daphnia and other zooplankton (a general term for any very small animals and insects).

Danger in shallow water

Although shallow waters are safe from larger fish, they are by no means a danger-free zone.

Mainly we know that dragonflies are master hunters of the skies. However, his childhood is spent in the warm, muddy shallow waters of the lake.

Here they wait, ready to ambush unsuspecting prey with a unique jaw (called a lip) that opens to grab a passing minnow, insect, or even tadpole.

Darner's Green NymphEmily took this photo as part of her university thesis. It’s hard to get this Green Darner nymph to sit still under a microscope!

These shallow waters are home to many other hunters lurking in the brush. Some chase their prey like the giant diving beetle. Others lurk like water scorpions, their long front legs outstretched, not unlike rapacious mantises, waiting for a hapless insect to swim by.

The hunters become the hunted.

While you may be concerned about the fish in the lake (considering that many of these insects love to eat fry), these same insects and their larvae also make tasty meals for larger fish.

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Sunfish, catfish and perch devour insects of all kinds, and where the forest of plants ends in the shadow of the depths, bass, pike and catfish catch stragglers who venture too far from the safety of the waters. shallow.

Out in the open: life in the limnetic zone

Now we can follow these larger fish into open water: welcome to the limnetic zone.

Here, far from the coast, we are in open water, high above any plants growing on the bottom.

Instead, the sun heats phytoplankton, small photosynthesizing algae (which convert sunlight into energy).


Just as there are many species of plants, there are also many species of algae!

While they are too small to see without a microscope, many have beautiful shapes and colors, and all convert sunlight and carbon dioxide into energy and oxygen for the lake.

Nutrient factories

Below this sunny (photic) zone, the light dims and darkens, until little or no light reaches the depths. Dead things accumulate here. Algae, fish, and dead plants eventually descend to the depths and rest in the thick mud.

Here, bacteria get to work breaking down dead matter, converting it into basic nutrients, and recycling those nutrients back to shallow waters via underwater currents. This completes part of the lake cycle.

We are part of a cycle

Each component within a lake, whether

  • The bigger fish keep the smaller ones at bay.
  • Aquatic plants and algae that provide food and oxygen.
  • Insects, the essential intermediary for plants and fish.

…each species is part of a greater whole.

Humans are also part of this community (ecosystem). We depend on and enjoy clean water for drinking, recreation, and eating, and yet our actions often endanger this same system.

Sailing in a canoe into the sunset,

Pesticides, herbicides, microplastics, and pharmaceuticals are found in our wastewater, roads, grass runoff, and stormwater. Manage and eliminate plants that provide energy and clean our waters; In many ways we are affecting our community, and not in a good way.

However, we can learn to be better. We can begin to see these connections between ourselves and nature and, through that, have a greater appreciation and desire to protect the biodiversity that sustains us.

The next time you kayak one of Ontario’s pristine lakes, take some time to reflect on its complex ecosystem, from the smallest oxygen-producing algae to the voracious Northern Pike, all beneath the waves.

“We cannot protect something we do not love,

We cannot love something we do not know,

And we cannot know something we do not see.

Or listen. Or sense.”

—Richard Louv