Date of Award


Degree Type


Degree Name

Master of Science in Oceanography


Biological Oceanography



First Advisor

Tatiana Rynearso


It is well known that morphologically cryptic species are routinely present in planktonic communities but their role in important ecological and biogeochemical processes is poorly understood. I investigated the presence of cryptic species in the genus Skeletonema, an important bloom-forming diatom, using high-throughput genetic sequencing and examined the ecological dynamics of communities relative to environmental conditions. Samples were obtained from the Narragansett Bay Long-Term Plankton Time Series, where Skeletonema spp. can comprise >95% of microplankton cells during blooms. DNA was extracted and sequenced from monthly samples between December 2008 and December 2013, and Skeletonema specific primers were used to exclusively target and differentiate known species. Seven species of Skeletonema were found in Narragansett Bay over the sampling period, including five species that were previously undetected in this location. Skeletonema community composition was highly seasonal, and temperature had the greatest effect on composition changes over time. Winter and spring communities demonstrated less species richness than did summer and autumn communities. These data suggest that a Skeletonema community can be comprised of different species, even in one estuary, and that seasonal changes appear to have a substantial effect on community structure, and perhaps important ecological processes, over time.



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