Bacteria associated with copepods: abundance, activity and community composition

We measured abundance, activity and community composition of bacteria associated with Calanus spp. in the North Sea in late July and compared it to the free living bacteria. Both the local density and production of bacteria associated with Calanus spp. were magnitudes higher than the average in a comparable volume of water. As analyzed by denaturing gradient gel electrophoresis (DGGE) and 16S rRNA gene sequencing, the bacterial community associated with Calanus spp. consisted of members of the Roseobacter lineage (Alphaproteobacteria), whereas the free living bacteria were more diverse. Discovery of an identical bacterial phylotype on Calanus spp. and in the free living community at the specific depth with the highest Calanus spp. biomass suggested an active exchange of bacteria between copepods and the free living state.