Looking beneath the surface: understanding freshwater ecosystems
The UN’s World Lake Day provides an opportunity to recognize the extraordinary value of lakes and the complex ecosystems they support. On this important day, Englobe is proud to spotlight our aquatic science expertise and the work our specialists undertake to understand, protect, preserve, and restore freshwater ecosystems for future generations.
A lake can appear tranquil from the shoreline. Beneath and around the water, however, is a constantly changing, rich ecosystem shaped by evolving relationships between fish, plants, insects, sediments, water temperature, surrounding vegetation, and the wider landscape.
Protecting fish often requires protecting fish habitat outside of the water, such as functional riparian areas. This is why studying is rarely about examining a single species, location, or environmental condition in isolation.
says Fonya Irvine, Senior Fish Biologist and Vice-President of Alberta-based Applied Aquatic Research Ltd. (AAR), an Englobe company.
Healthy riparian areas can help stabilize banks, regulate water temperature, and provide habitat for aquatic species.
A lifelong connection to freshwater ecosystems
Fonya’s interest in aquatic environments began along the Restigouche River in New Brunswick, where her father has worked as a guide for nearly 60 years
What I loved most was the cyclic nature of the river and its seasons. Fiddleheads emerged as the islands flooded following the spring ice run. Smelt returned at nearly the same time each year, schooling so tightly that they appeared as dark shadows beneath the surface. And, of course, Atlantic salmon made their way upstream, continuing a cycle that had repeated itself for generations and supported many livelihoods.
says Fonya Irvine.
A rich, complex natural environment
This early experience reflects a principle at the heart of aquatic environmental science: freshwater ecosystems are complex, dynamic, and interconnected.
Leaves and woody debris entering the water can feed invertebrates. Root systems help hold banks in place, while root tips can provide spawning substrate and rearing habitat. Above the surface, canopy shade can help maintain cooler water temperatures for cold-water species.
Together, these seemingly small elements influence whether an ecosystem can continue to support the species that depend on it.
How lakes reveal climate history
Interestingly, lakes can hold records of environmental change extending back through millennia.
During her graduate work, Fonya used two sediment cores to reconstruct July air temperatures at Trout Lake, in northern Yukon. She studied fossil midges and pollen, two independent biological proxies whose patterns tracked one another in relation to large-scale climate drivers.
She found that each sediment layer records conditions around the lake at the time it was deposited. Taken together, this information creates a climate ledger that continues to accumulate over thousands of years.
A lake sediment core can be thought of as a stratigraphic diary of the surrounding landscape and past environmental conditions.
says Fonya Irvine, Senior Fish Biologist and Vice-President of AAR.
Restoring connections between aquatic habitats can allow fish to reach areas that were inaccessible for generations.
Project work: from field observations to informed decisions
Aquatic environmental science also supports practical decisions about activities taking place in and around water.
A typical project may begin by:
- identifying the waterbody type
- determining whether fish are present
- reviewing seasonal timing windows
- assessing the proposed activity
Next, field assessments examine:
- fish habitat
- channel morphology
- riparian conditions
- and erosion risks
Then, specialists evaluate potential construction methods according to:
- habitat sensitivity
- water movement
- project constraints
Depending on the project, the work may also support environmental approvals, erosion and sediment control measures, fish salvage planning and contingencies, and post-construction monitoring.
Restoring connections within freshwater ecosystems
The complexity of freshwater ecosystems becomes especially apparent when part of the system is disrupted.
During an early stint at Parks Canada, Fonya took part in a master's student’s study at Forty Mile Creek in Banff, Alberta. There, a concrete dam built in the early 1900s had prevented bull trout from reaching their upstream spawning habitat for nearly a century.
When full removal proved unaffordable, one section was breached in 2014, allowing the creek to cut its own channel through the opening. Scientists tagged bull trout, released them below the breach, and tracked their movements.
Approximately one-third approached the opening. While that figure initially appeared low, an undisturbed control group upstream moved at almost the same rate. Of the fish that approached the breach, nearly 80% passed through it.
The study shows how a modest result can tell a different story when evaluated within a species’ broader behaviour and ecology. It also offers a tangible reason for optimism.
Freshwater systems can recover if given the chance. Removing a barrier can improve connectivity giving fish access to habitats that were once inaccessible.
says Fonya.
Aquatic environmental assessments help specialists understand fish habitat, channel conditions, riparian health, and environmental risks.
Analyzing pressures and possibilities
According to the United Nations, global freshwater species populations have declined by 85% over the past 50 years.
Freshwater ecosystems face overlapping pressures, including habitat loss, pollution, dams, overexploitation, invasive species, and climate change.
Changes in temperature, snowmelt, snowpack, and freeze-thaw events can also affect water availability in springtime and alter the conditions on which aquatic species depend.
Understanding connected ecosystems
Effective environmental decisions rely on considering freshwater environments as connected systems, and understanding their habitats, landscapes, species, climate patterns, human activities, and environmental processes.
Freshwater systems account for about 2.5 percent of all the water on Earth. Yet, they hold more than 10 percent of all known species, including about a third of all vertebrates and around 40-50 percent of fish. That's a diverse network of interconnected aquatic biota in a finite space.
says Fonya.
By collecting evidence, studying ecological connections, and identifying practical measures to reduce environmental effects, aquatic science specialists provide the knowledge needed to make better-informed decisions about these vital environments. "All life relies on freshwater and it’s in limited supply. Protecting freshwater ecosystems extends beyond conserving fish, it is an investment in our own health and that of future generations,” Fonya concludes.