The second in a series of West Conn's fall lake symposium lectures is being held tonight.  The subject of this event will be toxic blue-green algae, which has led to beach closures in the Greater Danbury area in recent years.  Two members of the state Department of Energy and Environmental Protection will lead the discussion about water quality.  An Associate Professor of Biological and Environmental Sciences will also talk about his research on Lakes Candlewood, Zoar and Lillinonah.  Blue-green algae can produce a harmful toxin that can cause symptoms from skin irritation to brain and liver damage.  Tonight's discussion is at 7pm in Route 125 of the Science Building on West Conn's midtown campus.