Spatial variability in bacterioplankton community composition at the Skagerrak-Kattegat Front

Abstract

The distribution of bacterial heterotrophic production and cell concentrations in the world oceans is well documented. Nevertheless, information on the distribution of specific bacterial taxa and how this is influenced by environmental factors in separate sea areas is sparse. Here we report on bacterial community structure across the Skagerrak-Kattegat front. The front separates North Sea water from water with a Baltic Sea origin. We documented community differences across the front using denaturing gradient gel electrophoresis (DGGE) analysis of PCR-amplified bacterial 16S ribosomal DNA and whole-genome DNA hybridization towards community DNA. Analysis of the community 'fingerprints' by DGGE revealed clustering of samples according to side of the front and depth. Consistent with these results, whole-genome DNA hybridization for 28 bacterial species isolated from the sampling region indicated that bacteria related to the Roseobacter clade and Bacteroidetes as well as prosthecate bacteria (e.g. Hyphomonas) showed distinct distribution patterns on each side of the front, and also with depth. Differences in bacterioplankton species composition across the frontal area were paralleled by differences in quantitative variables such as phytoplankton biomass (chl a), dissolved organic carbon, and bacterial production. Furthermore, we observed differences in more descriptive variables such as salinity range, bacterial growth-limiting nutrients and phytoplankton composition. We suggest that not only quantitative but also qualitative differences in variables that affect bacterial growth are required to cause divergence in bacterioplankton community composition between marine regions