MOLECULAR ECOLOGY OF MARINE DIATOMS, BACTERIA, AND THEIR BIOLOGICALLY-ACTIVE COMPOUNDS
This dissertation focuses on the molecular ecology of diatoms in the marine environment as it relates to co-occurring associated bacteria, spatial and temporal gradients of physical and chemical oceanographic parameters, and even biotoxin production. The study sites range from the polar habitat of t...
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DigitalCommons@URI
2021
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| Online Access: | https://digitalcommons.uri.edu/oa_diss/1277 https://doi.org/10.23860/diss-sterling-alexa-2021 https://digitalcommons.uri.edu/context/oa_diss/article/2290/viewcontent/Sterling_uri_0186A_12699.pdf |
| Summary: | This dissertation focuses on the molecular ecology of diatoms in the marine environment as it relates to co-occurring associated bacteria, spatial and temporal gradients of physical and chemical oceanographic parameters, and even biotoxin production. The study sites range from the polar habitat of the Southern Ocean (SO) surrounding the Western Antarctic Peninsula (WAP) to the productive estuary Narragansett Bay (NBay) in Rhode Island, USA. The WAP exhibits a naturally occurring gradient of a dissolved iron (Fe), which is an essential micronutrient that diatoms need for growth. Dissolved Fe is growth-limiting in the offshore area and replete in the nearshore areas. This provides a natural laboratory to examine how concentrations of dissolved Fe impact the native diatom communities, while also investigating the concentrations of Fe ligands produced by the co-occurring bacteria. The co-occurring bacteria may participate in a mutualism with the diatoms where bacteria produce Fe ligands to increase the bioavailability of iron to the diatom, increasing the diatoms’ growth while the diatoms in turn release additional dissolved organic carbon to support bacterial growth. Chapter 1 focuses on the in situ communities of diatoms and particle-associated bacteria in the iron-limited Southern Ocean. Community composition was assessed with high-throughput amplicon sequencing and analysis was performed to examine regional patterns that correspond to dissolved Fe and other metal and nutrient concentrations in addition to correlations with diatom and bacteria amplicons, which may indicate mutualisms. While there was a strong pattern in dissolved Fe concentrations with low concentrations offshore and higher concentrations closer to landmasses, there was no geographical pattern in the concentrations of siderophores, a class of bacterially-produced Fe-ligands. Both diatom and particle-associated bacterial community composition were similar by region sampled, indicating that metals, nutrients, and salinity may drive these taxonomic ... |
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