Several hundred thousand residents of the Toledo, Ohio, area remained Monday morning under an advisory not to drink their tapwater. Labs found microcystin, a toxin produced by blue-green algae, in the water. The algae are blooming in western Lake Erie, from which the city draws its water, because of phosphorus frpm farm runoff, lawn fertilizer, and sewage overflow. At a 3 am news conference, Mayor D. Michael Collins said the advisory would ramain in effect for some hours although tests showed microcystin in the water returning to safe levels. The crisis disrupted people's lives on a massive scale as bottled water was distributed.