Seasonal changes in the bacterial communities inhabiting particulate matter of different sizes

Abstract

We present a comprehensive study of the composition of the bacterial communities attached to particles and their temporal variations. We performed a 2-year study in a NW Mediterranean Sea coastal site (the Blanes Bay Microbial Observatory, BBMO). Monthly, 10 L of surface water were filtered sequentially through 6 size fractions: 0.2, 0.8, 3, 5, 10 and 20 µm. We 454-pyrosequenced the 16S rDNA and we processed the data with QIIME and Mothur. The results show an increase in the species richness when increasing the size fraction. More than 50% of the OTUs where specific of each fraction, suggesting that the six size fractions contain different types of particles that offer distinct microniches for the microorganisms and contribute highly in the differentiation of community composition between filters. Factors that cause important changes in bacterial community composition between size fractions and along time were episodic meteorological events, such as increases in continental runoff, and windstorms. Overall, our results indicate that a serial filtration through various filter sizes provides a more complete description of the bacterial communities attached to particles and their variability along time