Kosciusko County is a paradise for those who love lakes. Not only does the county boast over 100 lakes, but it’s home to Lake Wawasee, Indiana’s largest natural lake at 3,200 acres, and Lake Tippecanoe, the deepest natural lake at 122 feet.
Our beautiful lakes also hold much of our region’s history. In the 1920s, Winona Lake was home to evangelist Billy Sunday. His lakeside house is still toured by visitors! Indiana’s oldest sternwheel paddleboat, the Dixie, has been cruising Webster Lake for the past 80 years. We work hard to protect the lakes so future generations can share Kosciusko County’s legacy.
Protecting our lakes starts with knowing about them. To learn about Kosciusko County’s lakes, read the following information about lake ecology. You can become someone who makes a difference in their future! If reading about our lakes excites you, check out what you can do to help keep our lakes and streams clean.
Our lakes are fed from a variety of sources. Some water comes directly from rain, snow, ditches and streams. Other water comes indirectly, flowing downhill over land or through groundwater before making it to the lake. Water that comes indirectly, through a watershed, has a huge impact on water quality. They help determine the water quality of nearby lakes and streams. Any piece of land can be considered a watershed; the only qualification is that water must filter through it before reaching a body of water.
But why talk about watersheds? What makes them so important? Watersheds are the area of land that water flows over or through to get to a lake… and everyone lives in one! The water that hits your backyard (your watershed) will eventually make its way to one of our lakes. Soil that has been washed into a waterbody, organic materials such as leaves and plants, nitrogen and phosphorus from fertilizers, toxins, bacteria and other contaminants are all forms of watershed-produced pollution. What the rainwater filters through is doubly important because water doesn’t stop moving once it gets into a lake. It usually leaves that lake and continues moving until it gets to an ocean.
The actions we take on our property affect more than our lawn and driveway; they also affect our lakes and streams as well. It’s so important to treat the land around our homes and in our cities with care, not only the land along a lake or stream. If you are taking steps to protect water quality on your property, you are making a difference in the water quality of our lakes and streams no matter how far away from one you live.
Kosciusko County is part of the Glacial Lakes region of Indiana. This means that of all our lakes, most are natural lakes that were formed by activity from glaciers. As glaciers moved across the land, they formed lake basins in several ways. Sometimes they gouged holes in loose soil or soft bedrock which then filled up with water. In other places they left rocks and soil across stream beds, causing a natural reservoir. In some places they left behind buried chunks of ice that melted to leave basins filled with water. Any of these scenarios could create a glacial lake.
Many people think of lakes as static systems, but they are always changing – both throughout the seasons and over the years. In our region, we have distinct seasons. This causes the water temperatures in our lakes to have a seasonal pattern. In the spring, after the ice melts, the water is cold and the temperature is nearly the same throughout the whole lake. All the water is the same density, too. This is important because the more dense water is, the heavier it is. Since colder water is more dense, it will tend to sink to the bottom of the lake. When the water is all the same temperature and density, wind blowing across the lake lets the water mix easily and thoroughly. This is called seasonal lake turnover. After this turnover occurs in the spring, the air temperature rises. This causes the water at the surface of the lake to become warmer, but the water at the bottom remains cold. Since cold water is more dense than warm water, that colder water will stay at the bottom of the lake with the warmer water floating on top. Lakes that are deep enough usually end up forming three layers during the summer months. The top layer is the warmest surface water, which is usually fairly uniform in temperature. It’s called the epilimnion.
Below the epilimnion is the middle layer, where the water temperature starts to get colder. In this layer, the temperature decreases quickly until it reaches the bottom layer. This middle layer is called the metalimnion, or the thermocline. Last is the bottom layer of the lake, which holds very cold and dense water. Because this water is so much colder and denser than the rest of the water, it usually doesn’t mix with the other layers. This cold bottom layer is called the hypolimnion. As the weather cools in the fall, the surface water cools down as well. As the water gets colder, it gets denser. Eventually, the surface water and bottom water will approach the same temperature and density. At this point the wind can once again mix the water in the entire lake in what is called fall turnover. As winter begins, the water cools further until the surface water freezes over. Under the ice, most of the lake will be about 4 degrees Celsius for the winter season until the spring comes and melts the ice, and the process begins again. (image courtesy of Encyclopedia Brittanica)
Lakes undergo long term changes. They age! As a lake gets older it begins to gather leaves, dirt and other organic material at the bottom. Over time, this material builds up and slowly makes the lake shallower. A shallow lake allows more light to get into the water, allowing plant growth and warmer temperatures throughout the lake. More plants can lead to more plant material gathering at the bottom of the lake. When plants and other organic materials decompose underwater, they suck oxygen out of the water and it becomes difficult for some of our more popular game fish species to live. With enough time, a lake can actually fill itself with plant matter and disappear completely! This aging process, called “eutrophication,” is totally normal. In some places it takes thousands of years. In others it can happen very quickly. The following terms describe approximately how far along a lake is in this process.
- An oligotrophic lake is generally deep, has relatively few plants, is cooler in temperature and supports cold-water fish species. This would be a “young” lake.
- A eutrophic lake is generally shallow, has quite a few plants, is slightly warmer in temperature and supports fish species that can tolerate warm temperatures. This would be an “older” lake.
- A mesotrophic lake is somewhere between oligotrophic and eutrophic and could be called a “middle-aged” lake.
Being at a particular point in this process does not necessarily make a lake “good” or “bad.” Eutrophication is natural. However, this process, which could take anywhere from hundreds to thousands of years, can be accelerated by humans to a matter of decades. This is called cultural eutrophication, or making lakes “old” before their time. Cultural eutrophication is caused by land use practices around a lake, particularly those which contribute eroded soil that fills in lakes and nutrients like nitrogen and phosphorus that cause an overgrowth of plants in lakes. Taking care of our lakes involves slowing down the process of cultural eutrophication by careful evaluation and change of land use practices that contribute to it.
You may not observe much when you look at water, but there is a lot going on in there. When studying a lake, we are interested in a number of seen and unseen things. These include ion concentrations, dissolved oxygen, pH, nutrients that cause plant growth (nitrogen and phosphorus), chlorophyll (an indicator of algae) and bacteria.
Ions – Aside from the living organisms in a lake, there are a wide array of molecules and ions that come from soils in the watershed, the atmosphere and the lake bottom. Lakes that have high amounts of calcium and magnesium ions are called hardwater lakes, while those with low amounts of these ions are called softwater lakes. (Just like the water from your tap can be hard or soft!) The ions in a lake change the lake’s ability to absorb pollutants. For example, the calcium carbonate in a hardwater lake can take the form of marl. Marl helps remove the nutrient phosphate from the water. The total amount of ions in the water is called the total dissolved solids concentration. The total concentration and relative amounts of these solids influence the organisms that live in the water and natural chemical reactions.
Dissolved oxygen determines where organisms can survive in an aquatic system. Most fish need at least 5 mg/L of oxygen in order to live. When a lake is well-mixed, oxygen can be found at all depths. During the summer, however, many lakes become layered based on temperature and the bottom most layer has the least amount of oxygen. Chemical reactions that occur when organic matter decays. Since the bottom layer does not mix with other layers, it is not able to replenish its oxygen through mixing of lake waters. Oxygen depletion also occurs in the winter, when surface ice keeps oxygen from entering the water from the atmosphere. Oligotrophic lakes are nearly always well oxygenated, whereas eutrophic lakes are often depleted of oxygen.
The pH of water (how acidic or basic it is) is an important factor influencing aquatic life. Most aquatic organisms survive best in the pH range of 6.5-9.0. Anything higher or lower may interrupt important biological functions such as reproduction and respiration.
Phosphorus is a plant nutrient that has few natural inputs to lakes since it does not come from the atmosphere. It helps plants grow and enters water primarily through fertilizers, human and animal waste, and yard waste. Because phosphorus is the least abundant nutrient, it is often referred to as the limiting nutrient for growth of aquatic plants and algae and has the potential to cause excessive plant growth. Soluble reactive phosphorus (SRP) is dissolved phosphorus in a form that plants can immediately use. SRP is usually low in water samples since plants use phosphorus quickly. Total phosphorus includes all forms of phosphorus in the water, and levels higher than 0.03 mg/L can cause algal blooms. Phosphorus is often targeted in water protection projects because, in excess, it can cause undesirable plant growth and speed lake aging.
Nitrogen is an essential plant growth nutrient and can be found in fertilizers, human and animal waste, yard waste and air. Nitrogen gas makes up 80 percent of the air we breathe and naturally diffuses into water, where it is converted by blue-green algae into a usable form. Nitrogen also enters waters in the forms of inorganic nitrogen and ammonia. Nitrogen can be present in lakes in three forms. Nitrates (NO3) are dissolved nitrogen which is converted to ammonia by algae and are normally found in surface waters. Ammonium (NH4) is dissolved nitrogen which is in the preferred form for algae use. It is formed by the decomposition of organic matter and is usually found in the oxygen-depleted bottom waters of lakes. Organic nitrogen includes all the nitrogen found in plant and animal materials and can be dissolved or in particulate form.
Chlorophyll is the plant pigment that gives algae its green color. It’s an important part of the photosynthesis process. There are different forms of chlorophyll, but chlorophyll-a is the most common and measurements of it can be used to directly estimate the biomass of algae in a lake. If chlorophyll measurements are high, a lake may be in danger of an algae bloom occurring. Algae blooms cause large clumps of algae in the water, rotten smells and decreased water clarity. Furthermore, as the algae dies it sinks to the bottom of the lake and decomposes. The decomposition process uses up oxygen, causing the bottom waters of a lake to lose oxygen and become unsuitable for some kinds of fish. Some forms of blue-green algae also create toxins that have been found in several of our county’s lakes and can cause sickness in humans and animals.
Bacteria – Natural waters have a variety of microorganisms that live in them, including bacteria, viruses, protozoa, fungi and algae. Most of these are natural and have no effect on human health. There are, however, some microorganisms that do cause disease in humans and must be monitored. Viruses and protozoa cause many of the illnesses associated with swimming, but since they are often difficult to detect the bacteria E. coli is usually tested as an indicator for health risks associated with aquatic recreation. For water to be swimmable (or suitable for full body contact), the average of five water samples must not exceed 125 colony forming units (CFU) of E. coli per 100 mL of water and must never have one sample with more than 235 CFU of the bacteria per 100mL. Full body contact in water that exceeds these limits usually results in stomach illness that is easily treated, but in highly polluted waters disease may become more serious. E. coli bacteria is usually associated with the feces of warm-blooded animals and can come from humans, livestock and many other animals including wildlife such as geese and ducks.
In most lakes, the critters in them live in distinct areas. These areas are called zones and have special names to describe them. The littoral zone is the area near the shore where the lake is typically shallow and light can reach the bottom. This allows lots of aquatic plants to grow. Littoral zones are typically home to lots of plants like cattails, lily pads, pickerelweed, cardinal flower and coontail. You would also find turtles, frogs, mussels, wading birds, aquatic insects and some fish. The limnetic zone is the area of open water where light is not able to penetrate all the way to the bottom of the lake. This zone is usually towards the middle part of the lake where the water is open. You would not find many plants here. This zone would be home to a variety of fish and some aquatic insect species. In the littoral zone, there is a special area called the euphotic zone, which is where light can reach. The euphotic zone is where algae grows. Finally, the benthic zone is the bottom of the lake. It’s home to rich organic sediments and lots of invertebrates like worms and aquatic insects. Some organisms are able to move freely throughout these zones, such as fish, amphibians, turtles and insects. Others, like plants, aquatic insects and other invertebrates are restricted to certain areas. Still others such as zooplankton and algae ride wherever the water takes them.
Image courtesy of Water on the Web
Notes: For more detailed information on lake ecology, you can read the Lake Ecology Primer.