| Two California reservoirs were studied to determine the cause of an Anabaena flos-aquae bloom, the distribution of an A. circinalis bloom, and the effectiveness of two reservoir management techniques, hypolimnetic withdrawal and copper sulfate application, in controlling geosmin. Calero Reservoir is a small reservoir in northern California, and Lake Perris is a mid-sized reservoir in southern California. In the fall of 1991, microcosms were placed in the reservoir to learn whether A. flos-aquae was nutrient-limited and, if so, which nutrient was limiting. A Dinobryon species dominated when NO;Lake Perris in southern California typically has a bloom of Anabaena circinalis, chlorophyll a in the spring. The horizontal and vertical distributions of A. circinalis, chlorophyll a, and geosmin were observed during the April 1992 bloom and again immediately after the bloom was treated with copper sulfate.;During the April 1992 bloom, A. circinalis, chlorophyll a, and geosmin were all heterogeneously distributed over the surface of the reservoir. Geosmin was detected from the surface to 3 m during the bloom. The day after copper application, A. circinalis and chlorophyll a remained heterogeneously distributed over the lake surface, but geosmin distribution became homogeneous.;Horizontal geosmin distribution was independent of blue-green algae distribution during the April 1992 Lake Perris bloom. There was a positive correlation between chlorophyll a and A. circinalis, a very weak but significant correlation between geosmin and A. circinalis, and no correlation between chlorophyll a and geosmin.;Although the average geosmin concentration decreased from 177 to 123 ng/L after copper treatment, the range of concentrations increased and the highest post-treatment concentration exceeded the highest pretreatment concentration. The increase in maximum geosmin concentration after CuSO;Nitrogen, but not phosphorus or iron, was limiting algae growth in Lake Perris in March 1992. Fragilaria and Chlorella grew successfully in microcosms with nitrate added to them but, despite a potential ability to fix N... |
