Beneath the Surface

You probably love your lake and want to preserve it for future generations – so does our team!

Beneath the Surface will equip you with information that will give your family, organization or agency the ability to care for the lakes. A special thank you to The Papers and the Renda family for making this publication possible.

The Lilly Center launched back in 2007. We believe that a countywide lakes culture needs countywide research, education, and collaboration, so our team crafts original content for those in kindergarten through retirement. Due to the Lilly Center’s work, the lakes in Kosciusko County are some of the best studied in Indiana.

We have a library of valuable data that shows patterns and trends in the health of our lakes, which in turn reveals specific management steps. That’s part of the design of this report. After looking at the data, we encourage you to follow the action steps on page 49 and share it with others. A digital copy can be downloaded below.

We invite you to dive Beneath the Surface with us! Keep scrolling to see the combined data and analysis from this year’s report.

Have you noticed that you assess water clarity when you look off of a pier into the lake or down at your toes while swimming? You take note of whether or not you can see the bottom, or if sinking things disappear into murky depths. The Lilly Center quantifies water clarity using a black-and-white circle called a Secchi disk. Water clarity is reduced by the “stuff” suspended in the water – usually soil particles and algae. A deep Secchi disk reading, represented by a longer bar on the graph below, means clearer water. Clearer water is a sign of less algae and sediment in your lake!

This Secchi disk graph shows the maximum, average, and minimum depths we could see into each lake across all 11 of our weekly measurements during the summer of 2024. The average of all summer 2024 clarity readings was 5.9 ft, compared to 6.7 ft in 2023 and 6.8 ft in 2022. But not every week or lake was the same as last year! Take a look at the individual lake pages, starting on page 18, for more in-depth water clarity comparisons across the past three years.

We are not the only ones interested in water quality; fish rely on healthy lakes, too. One threat to Kosciusko County fish is a lack of dissolved oxygen in the summer.

As microbes, fish and other organisms live and “breathe” in the cool, deep water (hypolimnion), the dissolved oxygen content can diminish to zero, forcing fish into the much-warmer upper layer (epilimnion). The stark contrast in water temperature from top to bottom creates these epilimnion and hypolimnion layers, a boundary that dissolved oxygen and some other molecules cannot pass through until autumn cools the top water again. That is when water moves freely from top to bottom, replenishing dissolved oxygen throughout the lake.

By reducing the amount of material decomposing at the bottom of a lake, we can hopefully slow the use of dissolved oxygen and reclaim deeper, cooler water habitat for fish during the summer!

The lakes in this graph are organized from shallowest to deepest at their deepest point (gray bars show total depth). The longer the colored bars in this graph, the deeper the oxygen, the more habitat there is for fish! At bare minimum, fish require at least 2.0 mg/L of oxygen in the water to survive, so the colored bars represent where dissolved oxygen was measured greater than or equal to 2.0 mg/L. Many species of fish, however, need three or more times that amount to thrive and produce healthy offspring, and many rely on colder temperatures than can be found in the oxygenated upper layer of lake water in the summer.

The four graphs below show two nutrients (phosphorus and nitrogen) in two layers of lake water: the epilimnion and the hypolimnion, defined on the previous page. In order to get a full picture of lake nutrient levels, we sample both layers.

Phosphorus and nitrogen are nutrients that directly influence lake health. They are chemical elements necessary to support aquatic life, starting with the rooted plants (weeds) and phytoplankton (algae) that make up the base of the food chain.

Nutrients have a positive, healthy connotation for people. Just as eating too much or the wrong foods can be bad for human health, too much phosphorus and nitrogen can damage our lakes and their aquatic residents.

The gray line on each of the nutrient graphs marks the Environmental Protection Agency’s (EPA) calculation of the nutrient content of high-quality lakes in our area. It is a low bar compared to our results; in this graph, a shorter bar is more beneficial. According to our data from the past three years, all 14 lakes we sample need fewer nutrients to increase water clarity and the depth of fish habitats.

Note that the scales on these graphs are different, highlighting the fact that there are typically more nutrients in the hypolimnion than epilimnion in our lakes. That indicates that nutrients are not only coming from inflowing streams, but the lake bottom itself, too. (This is called “nutrient loading”.)

You can also see that Big Chapman, Syracuse, and Waubee lakes have relatively low total phosphorus concentrations in their hypolimnion layer, indicating less nutrient loading from the sediments in these lakes at their deepest point.

The EPA guideline for total phosphorus is 0.010 mg P/L. The average total phosphorus across all 2024 epilimnion samples was 0.029 mg P/L, while the hypolimnion was 0.213 mg P/L. The EPA total nitrogen guideline is 0.43 mg N/L. The 2024 overall average total nitrogen was 0.1.02 mg N/L in the epilimnion and 2.21 mg N/L in the hypolimnion.

Blue-green algae (BGA) are a photosynthesizing, increasingly-prevalent, potentially toxin-producing family of bacteria natural to freshwater. Not every species of BGA creates toxins, and the toxin-producing species do not always produce toxin. Though BGA are abundant in our lakes, data from the past four years shows that microcystin toxin averages at or near levels of concern for pets (0.8 ppb). While our BGA are capable of producing higher levels, typical levels do not approach the IDEM’s guideline for human health concern (8.0 ppb; four times higher than this graph’s scale) for our lakes.

Most of the Lilly Center’s time spent investigating our lakes does not take place on the water at all, but in a lab! A team of trained undergraduate students, lead by Grace College professor Dr. Joseph Frentzel, have spent the summer of 2022 identifying and counting thousands of individual algae cells.

Out of all water samples assessed so far, 74% of cells have been blue-green algae rather than green algae or other cells, and 62% of the BGA genera, or groups, found in our lakes are capable of producing toxin. 21% of our summer microcystin samples exceeded IDEM’s pet recreation threshold.

Thanks to results from last year’s Decade Lake Study, we determined that a second blue-green algae toxin deserved further investigation. More research is needed to better understand saxitoxin and the triggers that cause BGA to produce and release this toxin. But like microcystin, saxitoxin can cause harm to pets and humans in elevated quantities. (0.05 ppb and 0.8ppb respectively). Stay tuned as we continue to gather data about saxitoxin, identify areas of improvement, and suggest solutions for prevention.

Saxitoxin levels were higher in 2024 than in 2023, similar to the trend seen with microcystin. Only Center and Pike lakes saw a drop in saxitoxin concentrations this summer. Despite the general increase, most saxitoxin levels remained well below the dog safety threshold of 0.05 ppb. The exception was Silver Lake, where the average saxitoxin concentration reached 0.06 ppb. Six out of ten samples from Silver Lake exceeded the safety limit for dogs. Given the rise of microcystin and saxitoxin this summer, we might expect their levels to increase together. In some cases, like Silver Lake, that is what happened — both toxins showed high concentrations. However, in other lakes where microcystin levels spiked, saxitoxin did not follow suit. For example, at Waubee, Wawasee, Big Chapman, and Beaver Dam lakes, microcystin levels increased substantially, but saxitoxin stayed the same or even decreased. Webster Lake showed the opposite pattern, with an increase in saxitoxin and a drop in microcystin. We will continue studying saxitoxin and digging into the data to explore potential connections between the production of these two toxins.

Use the buttons below to download previous editions of Beneath the Surface.

We study 16 lakes, all of which are represented in Beneath the Surface:

• Beaver Dam Lake
• Big Barbee Lake
• Big Chapman Lake
• Center Lake
• Dewart Lake
• James Lake
• Oswego Lake
• Pike Lake
• Silver Lake
• Syracuse Lake
• Lake Tippecanoe
• Lake Wawasee
• Waubee Lake
• Webster Lake
• Winona Lake
• Yellow Creek Lake

Download a copy to find out the current state of your lake’s health.

Want to get involved at the lake-level? Find out if your lake has a lake association, or if one of the many local governmental/conservation associations is taking volunteers. Here are the ones we regularly partner with.

Beneath the Surface is made possible by The Papers, and the Lilly Center’s blue-green algae research is supported by K21 Health Foundation, among many others generous families and individuals. Thank you!