By Pat Jenkins The Dispatch Eight lakes in Pierce County remained risky places last week to swim. Advisory warnings about toxic algae that have been posted at the lakes throughout most or all of the summer by the Tacoma-Pierce County Health Department remained in place as of last Thursday, the most recent update. The lakes are being checked weekly by health authorities until advisories are lifted. The lakes include Ohop, Silver, Harts, Tanwax, Spanaway, Whitman, Twin Lakes and Waughop. Under the Health Department's advisories, lake users are urged to:. " Not swim or water ski in areas with visible algae, which looks like paint or scum on the water surface. " Keep pets and livestock away and not let them drink the water. " Thoroughly clean fish that are caught in the lakes and discard their guts. The algae can people sick or kill them if they stay in the water too long. It can also be fatal for pets, waterfowl and other animals, too. No fatalities or serious ailments from the algae have been reported. Toxic algae can reproduce rapidly in fresh water with the right amount of sunlight, warm temperatures and nutrients. Within a few days, a previously clear lake, pond or ditch can become discolored with the growth, which can form a layer several inches thick near shoreline. Wind and weather conditions can change the amount and location. If the algae becomes too prevalent, authorities can close a lake and tell people to stay out of the water, the next stage after the advisories that have been in place this summer. The toxin-bearing algae, also known as cyanobacteria or blue-green algae, looks like green or brown paint. It's naturally occurring, but likely has increased through human activities in and around the lakes, according to the Health Department.