A spot on Center Lake, Warsaw, is unfrozen. A warmer-than-usual winter has resulted in less ice forming on the local lakes. (Photo by Amanda McFarland)

KOSCIUSKO COUNTY — Northern Indiana winters are not always the same from year to year and, for 2015-2016, temperatures have run a bit warmer, making for thinner, shorter-lived ice cover on the local lakes.

Ice cover can affect a multitude of things when it comes to a lake.

According to Dr. Nate Bosch of the Center for Lakes and Streams, because of warmer temperatures this winter, it took longer for the lakes to freeze over this winter and the ice covers have not been as thick, reaching an average of 3-5 inches.

Pike Lake, Warsaw, and Syracuse Lake and Lake Wawasee, Syracuse, reached six inches while Lake Tippecanoe, Leesburg, reached seven.

“The relatively thin ice we have this year is in strong contrast to last winter, when typical thicknesses got up to approximately two feet,” Bosch said.

All of these factors can affect a lake’s ecosystem.

Bosch noted that ice, especially when covered with snow, blocks sunlight, making the water colder and darker. This, in turn, causes phytoplankton, or algae, and aquatic plants to die and decompose.

“The oxygen concentration of the lake declines as dead algae and plants decompose, or break down, on the lake bottom,” Bosch said. “As the algae and plants decompose, they use up oxygen. Declines in oxygen worsen if too many nutrients subsisted in the lake during previous seasons because nutrients cause more plants and algae to grow.”

In addition, the ice cover prevents air-to-water oxygen transfer and blocks sunlight, which decreases phytoplankton activity, causing the phytoplankton to produce less oxygen.

“As ice restricts oxygen flow to the lakes, the lakes only have a limited amount of oxygen prior to using up their supply in the winter,” Bosch said. “This has important implications for fish, as they continue to rely on oxygen in the water despite a reduction in their activity. An exhaustion of oxygen results in fish kills.”

With thinner ice this year and less snow cover, he added, fish kills should not be as severe as they were following previous, harsher winters.

Smaller, shallower lakes may see thicker, longer-lasting ice cover, according to Bosch, especially in areas sheltered by trees.

“So the impacts of less oxygen and less phytoplankton activity might be more severe on these lakes,” he said.

From a scientific standpoint, Bosch noted that there is always room for improvement in the local lakes.

“Our Lakes are mostly fair, but they could be much better,” Bosch said. “Our center is making our lakes clean, healthy, safe and beautiful.”