Graduate Thesis Or Dissertation
 

Evaluation of different monitoring strategies for public health protection : harmful algal bloom surveillance at Devils Lake, Lincoln City, OR

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https://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/cn69m7046

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  • Cyanobacteria are photosynthetic bacteria capable of producing toxins, including complex cyclic peptides called microcystins. Hazardous cyanobacterial blooms are an emerging public health concern and are monitored throughout Oregon in various recreational and drinking water bodies. Oregon has been proactive and responsive to the problems associated with toxic cyanobacterial blooms, but monitoring is challenging due to the heterogeneity of cyanobacteria blooms. The guidelines provided by state and international agencies are specific for some aspects of monitoring, but lack specificity in other areas. The specific aims of this study were to: 1) characterize the temporal and spatial distribution of microcystin in Devils Lake over the course of a cyanobacterial bloom, 2) evaluate the effectiveness of different monitoring strategies to assess the temporal and spatial occurrence of microcystin in Devils Lake in excess of public health guideline values and, 3) compare the strategies examined in this study to existing guidelines and provide an approach for harmful algal bloom surveillance in recreational waters in Oregon. Microcystin was first detected in Devils Lake on July 8, when Microcystis and Anabaena were first observed in a plankton sample. The seasonal maximum concentration (22.8 µg/L) occurred a month later on August 5. All samples were at or below the limit of detection by October 1. Microcystin distribution in Devils Lake was heterogeneous and variable, including inconsistent results between morning and afternoon microcystin concentrations. Based on these data, specific recommendations were developed regarding the type of samples that should be included in a monitoring plan and the number of samples to be collected at each site. Recommendations were also highlighted regarding sample frequency and duration. This research confirmed the importance of collecting a vertically integrated sample when genera that are capable of regulating buoyancy are present. Our data also supported including a plankton analysis in weekly visual site inspections, a method of monitoring that is currently underutilized in most guidelines. In addition, data indicated toxin analysis might be required more frequently than implied by current guidelines. These results, while limited to one site and sample season, should be considered in public health surveillance programs for potentially harmful cyanobacteria.
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