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Ciliate Micrograzer Dynamics of the New England Shelf

Emily Brownlee, Ph.D., 2017
Heidi Sosik, Advisor

Protists play important roles in marine ecosystems, but quantifying these roles has been hindered by difficulties in collecting and observing these often-delicate cells. During long-term deployments at the Martha’s Vineyard Coastal Observatory (MVCO), Imaging FlowCytobot (IFCB) made it possible to study live herbivorous and mixotrophic ciliates in situ without the need to culture or preserve. To study a more complete population, I coupled a ‘live cell’ fluorescent stain with a modified IFCB so that protists not containing chlorophyll can also be recorded. Staining IFCB (IFCB-S) revealed higher abundances of grazers than the original IFCB, as well as some cell types not previously detected. To analyze a 10-year time series of herbivorous ciliates at MVCO and address patterns of seasonality, I employed a statistical model that separates seasonal density patterns and annual-scale effects. To explore how well IFCB images can be used to detect seasonal community change, I used high-throughput sequencing (HTS), which does not discriminate between chlorophyll-containing cells and the rest of the community. I report on species and genera of ciliates for which morphotype and genotype displayed high congruency. I found HTS was critical to detect and identify certain ciliates occupying a niche associated with warmer temperatures.