Final Report Summary - ROMEO (ROle of crustacean zooplankton on prokaryotic community composition in the MEsopelagic Ocean)
The aim of the project was to determine the influence of metazoan zooplankton exhibiting diel vertical migration on the prokaryotic community in the Atlantic Ocean. Therefore, copepods’ samples were collected during two cruises (MEDEA I & II) in the North Atlantic Ocean. In order to address the main research questions, we used 454-pyro-sequencing of the 16S rRNA gene to obtain a detailed overview on the prokaryotic community composition associated with copepods’ gut (of different species) in the mesopelagic layers and to compare it with that of the ambient waters. Thus, the sequencing data obtained from the MEDEA I cruise samples was used to investigate the differences between the bacterial community composition associated with two orders of copepods (Cyclopoida and Calanoida) and the bacterioplankton community collected from the two boundary depth layers (~750 m, 100 m depth) at the same location as the copepods were collected.
Our data showed significant differences between the bacterial communities associated with the dominant copepods families (Calanoida, Centropagidae; Calanoida, Clausocalanidae; Cyclopoida, Corycaeidae; Cyclopoida, Oncaeidae; Cyclopoida, Lubbockiidae) and the ambient water. Bacilli and Actinobacteria dominated the copepod-associated community and Alphaproteobacteria, Deltaproteobacteria and Synechococcus dominated the free-living community. However, the presence of shared bacterial OTUs between these two distinct habitats suggests a dynamic exchange of bacteria from seawater and copepods. Taken together, our results support the hypothesis that the interior and exterior surfaces of copepods provide a specific niche with a strong selective pressure for bacteria.
Our data showed significant differences between the bacterial communities associated with the dominant copepods families (Calanoida, Centropagidae; Calanoida, Clausocalanidae; Cyclopoida, Corycaeidae; Cyclopoida, Oncaeidae; Cyclopoida, Lubbockiidae) and the ambient water. Bacilli and Actinobacteria dominated the copepod-associated community and Alphaproteobacteria, Deltaproteobacteria and Synechococcus dominated the free-living community. However, the presence of shared bacterial OTUs between these two distinct habitats suggests a dynamic exchange of bacteria from seawater and copepods. Taken together, our results support the hypothesis that the interior and exterior surfaces of copepods provide a specific niche with a strong selective pressure for bacteria.