: The goal of this effort is to complement the juvenile sucker sampling program of the USGS in order to establish connections between the health of the age-0 juvenile population, including direct pathological evidence of toxin exposure and indirect evidence of mortality through declining summer populations. To that end, the following are the specific objectives: Objective 1. To establish the spatial and temporal occurrence of toxins in lake sediments in areas of Upper Klamath Lake, Objective 2. To relate the occurrence of toxins in sediments to the toxin content and physiological state of settling blue-green algal colonies in the water column at the site, and Objective 3. To relate the spatial and temporal occurrence of toxins in the lake sediments to seasonal bloom dynamics and spatial characteristics of wind-driven circulation.