Clear water isn’t what ecologists want. Here’s why.

For Canada Water Week, March 21 to 27, explore freshwater issues at the heart of WWF-Canada’s work.
Written by Anthony Merante, Associate Specialist, Watershed Reports 
What is water quality? To some, it’s a glass of drinking water. To others, it’s a clear pristine glacial lake reflecting the blue sky. But ask this same question to an ecologist and they will paint a different picture.

Sioux Nation participants preforming water quality monitoring during the CABIN field practicum training. Credit: Raegan Mallinson / Wildsight
Sioux Nation participants preforming water quality monitoring during the CABIN field practicum training. Credit: Raegan Mallinson / Wildsight

They will use the light greens of algae and the dark browns of soils to describe productive, healthy aquatic ecosystems. When describing the quality of the water, they will use words like nutrients, metals, acidity and productivity. In reality, these are the parts of the picture that make up what water quality really is: the contents and chemistry of our rivers and lakes.
Photo by: Marilyne Robidoux An experiment on the effects of nutrient loading to freshwater communities. Pictured are mesocosms containing dissolved organic carbon, A component of water quality which browns water and reduced light penetration.
An experiment on the effects of carbon loading to freshwater communities. Pictured are mesocosms containing dissolved organic carbon, a component of water quality which browns water and reduced light penetration. Photo by: Marilyne Robidoux

Consistent and continuous monitoring of water can give insight into trends of rising levels of nutrient or metal content or restored health. Each parameter of water quality such as dissolved oxygen, pH, nutrients, dissolved organic carbon, metals) has thresholds provided by provincial, territorial or federal governments. These thresholds can have different effects on the ecosystem and the animals.
As an example, let’s look at phosphorus, which has been extensively studied as the root cause of algae blooms like those of Lake Erie. Commonly found in fertilizers, phosphorus has an effect that starts at the very base of the aquatic food web. In an aquatic food web, phosphorus is like a piece of chocolate cake the day after your diet ends, ready to be to eaten the second it enters the room. Just like chocolate cake, in moderation it won’t do any damage, but overindulgence can lead to negative outcomes.
Algae Bloom in Lake Erie, acquired July 28, 2015. © NASA Earth Observatory
Algae Bloom in Lake Erie, acquired July 28, 2015. © NASA Earth Observatory

Algae species, which form the base of the food web and are sources of omega-3s, are the first consumers of phosphorus. If readily available, algae will consume phosphorus at an unsustainable rate, ultimately starving when the phosphorus is gone. During the time of consumption, algae grow immensely and create blooms blooms that die off and remove oxygen from the water in their decaying process.
With reduced oxygen in the water, larger species such as fish will die off. In this scenario, both the bottom and the top of the food web in many freshwater systems are lost. Small changes in water quality can have cascading effects, shifting the food web dynamic and reducing the biotic community. These impacts, however, do not stop in the water. The aquatic food web is deeply linked with the terrestrial food web, providing nutrition via fish to large predators such as bears and birds.
This scenario shows the importance of aquatic health monitoring by checking water quality to track changes in our water’s contents and chemistry. To learn more about your community’s water quality and other threats to freshwater check out watershedreports.wwf.ca.
Image of WWF-Canada’s Freshwater Health Assessments, examining the metric of Water Quality along the Quebec-Ontario border in the Ottawa basin.
Image of WWF-Canada’s Freshwater Health Assessments, examining the metric of Water Quality along the Quebec-Ontario border in the Ottawa basin.