Do buy stock in companies that make deet and other repellents. Mosquitoes and gnats can be fierce throughout spring and summer.
The algae bloom is a result of drought conditions in the Williamson and Sprague River drainages. The Wood enters the lake near Fort Klamath, and is spring fed. I caught and released the largest trout on the Wood, near where in joins Agency Lake.
The upper Williamson, near Yamsey Mtn used to be a tremendous fishery for red band and brook trout, but low water and warm temps have impacted it. One of my fishing partners reported the stream had significantly weeded in in that area. The upper Sprague also has browns.
Afterthought: when fishing the lower Williamson, always use a wading staff. In many places the bottom is basalt, with potholes. More than one person has floated their hat in that stretch of water.