First Advisor

Anne Thompson, PhD

Date of Award

Spring 6-16-2024

Document Type


Degree Name

Bachelor of Science (B.S.) in Biology and University Honors






Prochlorococcus, Appendicularians, Zooplankton, Cyanobacteria, Marine microorganisms, Microbial ecology


Prochlorococcus is a globally abundant cyanobacterium that can help reveal the ecology of microorganisms in the ocean. Specifically, mortality by zooplankton such as appendicularians is globally important and Prochlorococcus can help reveal some of the choices made around feeding for this ubiquitous filter feeder. Two ecotypes of Prochlorococcus were introduced to appendicularians to determine if appendicularian feed selectively between these ecotypes. Further, a single ecotype of Prochlorococcus was fed to appendicularians over a variety of life stages to determine if retention rate changed with appendicularian life stage. My results reveal that there is no significant selection between the two Prochlorococcus ecotypes (as supported by a p-value of 0.35), and retention of Prochlorococcus cells by appendicularians increased with grazer developmental stage. Lack of discrimination between the two ecotypes reveals that the two similar Prochlorococcus ecotypes fulfill a similar feeding trend for the appendicularians. Further work should be performed to determine if increased retention rate of Prochlorococcus cells coincides with appendicularian physiological changes during development. This research helps in understanding the differences and similarities in the microorganisms that appendicularians choose to feast upon and why these microorganisms are chosen over others.