Natural Winterkill Impacts Local Ponds And Lakes In Iowa City

Press release from the City of Iowa City:

March 17, 2021

The Iowa City Parks and Recreation Department has received reports of dead fish spotted in local bodies of water as the ice cover disappears following warmer temperatures. This winterkill occurs when ice barriers form on the surface of lakes and ponds, preventing oxygen circulation.

Iowa's winter weather included an accumulation of ice, blanketed by snow, which covered bodies of water for an extended period, and blocked crucial sunlight. This scenario impedes photosynthesis, which can cause aquatic plant life to die. The loss of aquatic plants results in less oxygen under the icy surface, ultimately causing the loss of fish. These winter fish kills are part of a natural cycle.

The Iowa DNR reports that fish kills are common at this time of year across the state. Although the number of impacted fish may appear to be large, it is rarely enough to have a lasting impact on pond health or the larger fish population.

Parks maintenance staff remove the dead fish as time allows during regular park maintenance.

This press release was produced by the City of Iowa City. The views expressed here are the author’s own.