If you plan on heading to the lake this weekend, some beaches are closed - due to high levels of bacteria.

The City of Madison has decided to close beaches at Olbrich Park, Warner Park, Verona Fireman’s Park, Hudson Park Lake Access Point and BB Clarke Park.

Bacteria levels are at unhealthy levels at all the beaches, officials discovered during tests this week. The beach closures will be lifted when those bacteria levels drop.

Part of the problem is that phosphorus emitted from cow manure and fertilizers used on farms is leaking into Madison’s lakes, according to the UW-Madison Center for Limnology.

That phosphorus then causes the algae to grow at unnaturally rates – making the lakes unhealthy to swim in.