Bacterial community succession in response to dissolved organic matter released from live jellyfish
Jellyfi sh blooms have increased worldwide, and the outbreaks of jellyfi sh population not only aff ect the food web structures via voracious predation but also play an important role in the dynamics of nutrients and oxygen in planktonic food webs. However, it remains unclear whether specifi c carbon compounds released through jellyfi sh metabolic processes have the potential to shape bacterial community composition. Therefore, in this study, we aimed to investigate the compositional succession of the bacterioplankton community in response to the dissolved organic matter (DOM) released by the live Scyphomedusae Cyanea lamarckii and Chrysaora hysoscella collected from Helgoland Roads of the North Sea. The bacterial community was signifi cantly stimulated by the DOM released form live jellyfish and different dominant phylotypes were observed for these two Scyphomedusae species. Furthermore, the bacterial community structures in the diff erent DOM sources, jellyfi sh-incubated media, Kabeltonne seawater, and artificial seawater (DOM-free) were signifi cantly diff erent, as revealed by automated ribosomal intergenic spacer analysis fingerprints. Catalyzed reporter deposition fl uorescence in situ hybridization (CARD-FISH) revealed a rapid species-specific shift in bacterial community composition. Gammaproteobacteria dominated the community instead of the Bacteroidetes community for C . lamarckii, whereas Gammaproteobacteria and Bacteroidetes dominated the community for C . hysoscella. The signifi cant diff erences in the bacterial community composition and succession indicate that the components of the DOM released by jellyfish might differ with jellyfish species.