Biology Theses and Dissertations
Permanent URI for this collectionhttp://hdl.handle.net/1903/2749
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Item Spatial and temporal variability of bacterioplankton communities across river to ocean environmental gradients(2012) Fortunato, Caroline Sara; Crump, Byron C; Marine-Estuarine-Environmental Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Bacterioplankton communities are deeply diverse within and across environments, yet also display repeatable patterns over seasonal and annual time scales. I assessed patterns of bacterioplankton community variability across the Columbia River coastal margin over space and time. Coastal zones encompass a complex spectrum of environmental gradients, which impact the composition of bacterioplankton communities. Few studies have attempted to address these gradients comprehensively, especially across large spatial and long temporal scales. I generated a 16S rRNA gene-based bacterioplankton community profile of a coastal zone from water samples collected from the Columbia River, estuary, plume, and along coastal transects covering 360 km of the Oregon and Washington coasts and extending to the deep ocean (>2000 m). Over 600 water samples were collected during four consecutive years and eleven research cruises. Spatially, bacterioplankton communities separated into seven environments across the coastal zone (ANOSIM, p<0.001): river, estuary, plume, epipelagic, mesopelagic, shelf bottom (depth<350 m), and slope bottom (depth>850 m). Communities correlated strongly with the structuring physical factors of salinity, temperature, and depth. Within each environment, community variability correlated with factors important to primary and secondary production. In the freshwater-influenced environments of the Columbia River, estuary, and plume, communities varied seasonally and reassembled annually. Freshwater SAR11, Oceanospirillales, and Flavobacteria taxa were indicators of changing seasonal conditions in these environments. In contrast, seasonal change in communities was not detected in the coastal ocean but instead varied spatially with environmental conditions. Each coastal ocean environment had distinct taxa including SAR406 and SUP05 taxa in the deep ocean and Prochlorococcus and SAR11 taxa in the upper water column. A survey of metabolic potential (metagenomics) and gene expression (metatranscriptomics) across the salinity gradient showed that although communities were taxonomically distinct, the metabolic potential of these communities was highly similar. Additionally, gene expression patterns were extremely different and reflected the short-time scales on which microbial processes persist in an environment. Across the coastal zone, bacterioplankton communities were taxonomically distinct but metabolically similar, structured by physical factors, and predictable across seasons from river to ocean.Item The regulation of bacterioplankton carbon metabolism in a temperate salt-marsh system(2005-09-21) Apple, Jude Kolb; del Giorgio, Paul A.; Kemp, W. Michael; Marine-Estuarine-Environmental Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)This study describes an investigation of the factors regulating spatial and temporal variability of bacterioplankton carbon metabolism in aquatic ecosystems using the tidal creeks of a temperate salt-marsh estuary as a study site. Differences in land-use and landscape characteristics in the study site (Monie Bay) generate strong predictable gradients in environmental conditions among and within the tidal creeks, including salinity, nutrients, and the quality and quantity of dissolved organic matter (DOM). A 2-yr study of bacterioplankton metabolism in this system revealed a general positive response to system-level nutrient enrichment, although this response varied dramatically when tidal creeks differing in salinity were compared. Of the numerous environmental parameters investigated, temperature and organic matter quality had the greatest influence on carbon metabolism. All measures of carbon consumption (i.e., bacterioplankton production (BP), respiration (BR) and total carbon consumption (BCC)) exhibited significant positive temperature dependence, but the disproportionate effect of temperature on BP and BR resulted in the negative temperature dependence of bacterioplankton growth efficiency (BGE = BP/[BP+BR]). Dissolved organic matter also had an influence on carbon metabolism, with higher BCC and BGE generally associated with DOM of greater lability. Our exploration of factors driving this pattern suggests that the energetic content and lability of DOM may be more important than nutrient content or dissolved nutrients alone in determining the magnitude and variability of BGE. Investigations of single-cell activity revealed that BCC and BGE may be further modulated by the abundance, proportion, and activity of highly-active cells. Differences in single-cell activity among creeks differing in freshwater input also imply that other cellular-level properties (e.g., phylogenetic composition) may be an important factor. Collectively, results from this research indicate that the variability of bacterioplankton carbon metabolism in temperate estuarine systems represents a complex response to a wide range of environmental and biological factors, of which temperature and DOM quality appear to be the most important. Furthermore, this research reveals fundamental differences in both cellular and community-level metabolic processes when freshwater and marine endmembers of estuaries are compared that may contribute to the variability in bacterioplankton carbon metabolism within and among estuarine systems.