Prochlorococcuspredation by a globally abundant filter feeder

Abstract

Prochlorococcusis the most abundant photosynthetic cell on Earth and is critical to primary productivity and biogeochemical cycles of the open ocean. Appendicularians are ubiquitous gelatinous filter-feeding zooplankton that feed on marine microorganisms includingProchlorococcus. However, the details of this feeding interaction are extremely understudied relative to its potential importance in top-down controls onProchlorococcus. This is the first study to experimentally examine several dimensions of the feeding interaction between cultivated appendicularians and Prochlorococcus. We found thatProchlorococcusretention rates by the appendicularianOikopleura dioicaincreased with prey concentration and predator age. We found that appendicularians grazed equally on the two most globally abundantProchlorococcusecotypes HLI and HLII and that the presence of larger diatom prey did not changeProchlorococcusretention rates. The quantitative insight and retention rates provided by this study will help fill gaps in models of the marine carbon cycle and marine microbial community dynamics and biogeography, and expand the knowledge of Prochlorococcus ecology.