Frequently Asked Questions about Freshwater Science (Limnology)

Here at the world’s freshwater laboratory, we often get asked many, many questions about freshwater science (or limnology to its friends).

Here are just ten of our most frequently asked questions…

1. What is fresh water, and why do we need to protect it?

Fresh water supports all life on earth. Without water, we would not have the world we have today. Can you think of a time you forgot to water your garden or house plants? Without a drink, plants become droopy, brown, and will die if left long enough.

Humans depend on freshwater resources for survival and personal wellness. Freshwater lakes and streams are often important sources of food. Humans cannot drink salt water, so the fresh water held in groundwater, lakes, streams, and ice are all we have.

Human cultures across the world build water into their value systems. Lakes may be areas of inspiration and sustenance, while springs offer space for gathering, and rivers serve as connections between different ecosystems.

Research has shown that human actions – through things like water and air pollution, climate change, and habitat modification – can negatively impact the quality of water and the health of ecosystems. Changes to lakes and streams have the potential to harm the organisms that depend on that water resource for a home, for food, as a water source, and for personal or cultural wellness.

By understanding factors like algal blooms and acid rain, we can start to understand how fresh water is at risk and what we can do to help it.

Read more about fresh water here.

2. What is an ecosystem?

An ecosystem refers to an area where living things (e.g. plants, animals, bacteria) and nonliving things (e.g. sunlight, rocks, wind) interact with each other.

Imagine a forest floor. On that forest floor, you might see mosses, mushrooms, a dead tree, and bugs interacting with one another. At the same time, the sun helps the moss grow and water running off the tree canopy above you carries important nutrients for the mushrooms. If a human were to hike by and pick a piece of moss off that dead tree, they have interacted as a part of the ecosystem.

At IISD-ELA, we are most concerned with freshwater lake ecosystems.

This means some of our research applies directly to what and how organisms live in a lake, while other research applies to how terrestrial organisms or substances can affect what happens in a lake. The boundaries of ecosystems can change depending on the research being done, so there is never a dull moment in ecosystem science.

Whole-ecosystem science is an important pillar of environmental research. Ecosystem experiments allow us to factor in the complexity of the environment around us, which can improve our findings and help us understand our research in a global context.

Ecosystem-level experimentation is one of many approaches scientists use to answer big questions; other strategies include long term monitoring, lab experiments, and computer models. Work at IISD-ELA often involves different combinations of these strategies, which allows us to explore interesting and impactful questions about the environment.

3. What is a lake? 

Answering this question can be challenging because the actual definition of a lake varies. The basic definition of a lake is that it is a large, inland waterbody with slow-moving water.

Lakes form in different ways, range in depth and shape, differ in water chemistry, and interact with the surrounding landscape in different ways. Because of this variation, more specific definitions of lakes will differ depending on where you are in the world.

An individual person’s knowledge of waterbodies will also shape how they define and identify lakes. While one person may recognize a lake as an area for recreation, someone else may think about how a lake supports survival, and still another may identify lakes by their spiritual characteristics.

The great variability in lakes means that individual lake ecosystems vary and are unique. At IISD-ELA, we research lakes in the boreal ecozone of Canada. Boreal lakes are known to be cold, deep, seasonal, and have cold loving fish, like Lake Trout.

Click here to learn more about what a lake is.

4. What lives in a lake? How can you measure those populations? 

Lakes are complex and diverse ecosystems. Think about what you usually see in lakes: different kinds of fish, various aquatic plants, and maybe some clams and other invertebrates, too.

Lakes have a variety of water animals besides fish, including tiny animals that are too small to swim against currents (i.e. zooplankton). It’s also important to think about the animals that live in both the water and on land, such as beavers and loons.

In addition to the commonly seen aquatic plants like water lilies and duckweed, lakes are home to tiny water plants and algae (i.e. phytoplankton). Lakes also contain bacteria, including cyanobacteria, or blue-green algae, that can cause harmful algal blooms in springtime.

When it comes to measuring biota populations, IISD-ELA scientists recognize that it is a privilege to use other living things in our research. For this reason, we think carefully about how we can measure and collect data, while also reducing the potential for harm of these living things and the ecosystem overall.

Measuring fish involves methods that allow us to track behaviour (like acoustic telemetry tags), estimate population dynamics, and assess how fish respond to environmental changes (like slime sampling).

Measuring zooplankton and phytoplankton involves taking different kinds of samples from a lake, and often requires us to strain out these tiny organisms from bigger samples of water. In other words, we don’t have fishing rods small enough for zooplankton! Some cool pieces of equipment that we make in-house are our zooplankton nets (check out how we make them).

New methods are also emerging, such as eDNA and ultrasound imaging, that have freshwater researchers looking forward to faster and less invasive monitoring.

5. What is a limnologist?

Limnology is the study of inland water systems. This field focuses on the relationships between biological, chemical, and physical aspects of both fresh and saline inland waters. A limnologist is a person who does limnology.

Research in limnology is varied and unique. Limnologists at IISD-ELA focus their studies on inland water systems of the Canadian boreal ecozone and one of the backbones of IISD-ELA limnology is our long-term monitoring program.

For more on limnology and those who research it, click here.

6. What are invasive species?

Invasive species are living things that are introduced to an area to which they are not native.

Once introduced, these species can cause great damage to the habitat and its native species. Invasives increase competitive pressure on native species, take over habitats, and can drastically disrupt the native ecosystem’s dynamics.

Invasive species are introduced in different ways, like by catching a ride on the hull of a boat that moves between lakes. Once introduced, invasive species can be challenging to control because they no longer have the predators or diseases from their native range to control them.

In the boreal lakes of Canada, we are often concerned about zebra mussels. These mussels are successful colonizers and will often smother populations of native Great Lakes bivalves, like the black sandshell mussel. Once they invade a lake, they are near impossible to get rid of.

Invasive species research often looks at the environmental and socioeconomic impacts invasives have on an area and will strive to assess the efficacy of treatment options.

7. What is productivity? 

In general, productivity measures the efficiency of producing certain outputs from certain inputs (e.g. the number of bowls a potter can make from a block of clay). To an ecologist, productivity can be measured as the number of grams of carbon that biota can fix per metre squared in a specific time period.

An easy way to think about productivity is to consider how phytoplankton in a lake can grow during summer. Phytoplankton will use sunlight to make a number of grams of mass per day. In a lake, this productivity may be measured by collecting phytoplankton samples over a period of time and comparing the masses of phytoplankton present in each sample. This lets us see how efficiently carbon was fixed by the phytoplankton in that lake over the summer.

Productivity can be measured for any level of the food web. Primary productivity, for instance, refers to the productivity of organisms that can make their own energy and food (check out what role Carbon plays in this whole process).

As you can imagine, productivity is an essential part of any ecosystem and a lot of research is done to look at how changes to a lake may impact the productivity of the ecosystem. Understanding productivity of organisms at the base of the food web (like phytoplankton) is important for understanding the changes we see in any system’s ecology.

8. What are the potential impacts of carbon, nitrogen, and phosphorus in lakes?

Carbon, nitrogen, and phosphorus (also known as C, N, and P, respectively) are important elements for life and an important part of lake research. Levels of these chemicals in lakes can impact the health of aquatic ecosystems.

Indeed, one of the textbook studies from early years of the Experimental Lakes Area showed just how high P loads in lakes can cause algal blooms. From this research we have seen how too much of a good thing (e.g. a necessary nutrient) can ultimately be a bad thing for the ecosystem.

Seeing the role phosphorus plays in harmful algal blooms has also led us to consider potential solutions to issues associated with nutrient pollution. To learn more about what you can do about algal blooms, read this blog for some guidance.

Through recent follow ups to our eutrophication studies we have continued to assess how nitrogen factors into these algal blooms as well. We know that nitrogen is important for the growth of some algae, but more IISD-ELA eutrophication research has shown that limiting N additions does not reduce algal blooms.

Carbon serves an important role in the chemistry of lakes. Carbon helps regulate the acidity of a lake (i.e. its pH). In fact, pH is an extremely important feature of a lake for its food web. Small changes in pH can kill consumer species at the base of the food web, which in turn impacts other species in the lake.

Have you ever noticed how some lakes are clear and others are the colour of tea? Lakes with dark coloured water are that colour because they have higher concentrations of dissolved carbon than clear water lakes.

As we have learned through our Lake 626 Diversion Project, these levels of dissolved carbon don’t just impact how great a lake looks in photographs (and all lakes look great in their own way, BTW). Changing the levels of dissolved carbon in a lake can ultimately change temperature structure of the lake, which will impact water quality and the organisms living in the lake.

9. How does a lake change over the seasons? (What is stratification?) 

In temperate zones, like here in Canada, the state of a large, deep lake will change with the seasons. These changes are driven by changes in temperature and amounts of light hitting the earth.

One of the most important changes to a lake between seasons is called thermal stratification, or the development of layers within the lake based on water temperature.

During seasons with relatively stable temperatures, like summer and winter, lakes develop three water layers based on temperature. During seasons with relatively quickly changing temperatures, like spring and autumn, lakes go through a turnover period where those three layers are disturbed.

During mixing, the biological dynamics of the lake changes as well, as the mixing water will move nutrients around with it. In deep temperate lakes, this becomes a seasonal cycle: winter stratification, spring mixing, summer stratification, fall mixing, repeat.

10. How can I protect lakes? 

By reading this, you’ve already completed the first step! One of the most important things to do is to learn about lakes from people who are passionate about them.

This can be done in a variety of ways, like by asking a lake scientist why they do what they do, talking to an indigenous leader or member of a local first nation about the importance of water in their culture, or watching videos about what is being done to help lakes. The best thing about learning is that you can always learn new things.

Another great thing to do is to connect with the scientific research community as a citizen. Members of the public play an important role in observing and contributing to what we know about lakes and water. There are some specific things you can try, including volunteering with organizations like the Lake Winnipeg Foundation or contributing to citizen science efforts with The Gordon Foundation’s DataStream project .

Finally, be aware of lake friendly policies in your area and around the world.

Some things to think about include thoroughly cleaning water items before transferring to another water body to prevent invasive species movement, remembering that any wastewater you dispose of will return to our lakes and streams along with anything you put in it, and reading up on your local government’s environmental policies on air and water pollution. You can become a part of this by educating yourself on the health of lakes and then trying to encourage local politicians to also adopt lake friendly policies.

Water is a precious resource and we can all do our part to be stewards of our lakes.