Cosmopolitan Freshwater Bacterial Dynamics In Lakes Across Time And Space

Author : Melissa Lynne Partyka
Publisher :
ISBN 13 : 9780355461237
Total Pages : pages
Book Rating : 4.4/5 (612 download)

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Download or read book Spatiotemporal Variability of Bacterial Communities in Marine and Freshwater Ecosystems of California written by Melissa Lynne Partyka and published by . This book was released on 2017 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Microorganisms are fundamental members of aquatic and marine ecosystems capable of affecting the macroecology of these systems by serving as the foundation of complex food chains, biogeochemical processes, and disease dynamics. Though recognized as foundational, scientists continue to struggle to apply basic ecological concepts of like community, spatiotemporal variability, gradients, and disturbance regimes to microorganisms in meaningful ways due to the vast differences in scale between macrobial sampling designs and microbial existence. However, until new ecological concepts have been generated for understanding microbial populations, we must continue to sample varied habitats at multiple spatial and temporal scales with the hope of capturing both unique and common characteristics of these communities that will allow us to predict their responses to a changing environment. The ability to predict microbial behavior has particular importance for human health; for that reason, this research focused on bacterial members of the greater microbial community that have been associated with illness and disease in humans utilizing both culture and molecular techniques followed by multiple-regression analyses. In Chapter 1, the intention was to examine bacterial populations at broad spatial and temporal scales within 6 freshwater reservoirs in the foothills of the Sierra Nevada Mountains. We sought to understand whether microbial water quality within reservoirs was driven by upstream conditions and subsequently predictive of downstream outcomes. Specifically, this research sought to understand the variability of fecal indicator bacteria (Escherichia coli and fecal coliforms) and pathogens (E. coli O157:H7, Non-O157 shiga toxin-producing E. coli and Salmonella) along both horizontal and vertical profiles within California reservoirs as it related to upstream river sources and downstream irrigation water supplies. Continued monitoring and modeling of both bacterial indicators and enteric pathogens are critical to our ability to estimate the risk of surface irrigation water supplies and make appropriate management decisions. In this study, the extreme variability in microbial populations across both space and time made successful predictions largely impossible and underlined the extreme importance of sampling these dynamic communities at scales where their behavior can be observed, particularly where human health may be impacted. I sought to further refine the scale of examination in Chapter 2 which moved from the freshwater of the Sierras to the marine habits of coastal California. In these systems the bacterial genus Vibrio is both endemic and occasionally pathogenic. Thus, we strove for greater understanding of how four members of Vibrio, V. alginolyticus, V. parahaemolyticus, V. cholerae, and V. vulnificus, referred to as “the big four” of global human illness, interact with their environment and respond to changing conditions. We examined finer-scale spatial and temporal variability of the “big four” in one bay of Northern California, Tomales Bay, highly popular with tourists and known as a premier region for shellfish production. As with Chapter 1, bacterial populations were highly dynamic in both space and time. However, these data were more easily modeled by capturing weekly, daily, and occasionally hourly changes to the environment during seasonal storms and sub-meter differences in sediment characteristics during acute tidal cycles. As with the previous chapter, pathogen prevalence or concentration in water, sediment, or shellfish did not correlate (p>0.1) with concentrations of fecal indicator bacteria, suggesting the need for revisions to the current regulatory monitoring efforts. For the third and final chapter I chose to manipulate the environment experienced by microorganisms in a manner that is common to intertidal sand and mudflats along most coastlines, recreational clamming activity. The impact of physical disturbance by clamming activity on microbial communities of intertidal sand flats has received relatively little attention, though the state of California estimates that 20-40K clams are taken from California bays annually, suggesting many people are performing the behavior and a large volume of sediment is being moved. I examined these impacts through a replicated cross-factorial longitudinal experiment on two emergent islands at the mouth of Tomales Bay. By following these exact sites through time we were able to reveal a wealth diversity within a single species of Vibrio, V. alginolyticus, and examine how that diversity changed through recurring tidal cycles. Further, while it was apparent that our targeted species were not significantly (p>0.05) impacted by our experimental disturbances, there were clear differences in the responses of indicator bacteria (fecal coliforms and enterococci) and vibrios by location and across time. These data illustrate that a great deal remains to be discovered about human influence over microbial communities in coastal systems, opening the door for further refinement in study designs. Taken as a whole, this series of studies has helped to further highlight the need of studies that examine microbial populations not only at scales that are relevant to the organism under investigation, but to the humans that may encounter them and fall ill. I sought to provide suggestion to aid the regulatory community in modifying current guidelines in the interest of public health and to encourage the ecological community to continue to evaluate the impact of scale on our ability to make inferences and gain understanding of these unseen and complex microbial communities.