Seasonality of rare and abundant bacterial taxa in Radiales E2 Gijon/Xixon time-series station. E2microSEASON

In this 3-years time-series study in coastal waters of the Bay of Biscay we have identified the largest number of bacterial taxa with significant seasonality to date (83 taxa). Among these seasonal taxa, 24 cycled between rare and abundant, but most of them were always-rare (59 taxa), with maximum abundances predominately found in winter. We demonstrate that recurrent seasonal patterns in marine bacterioplankton are largely driven by lineages that never account >1% of total community abundance. Such dynamics characterized by seasonal growth and loss opens new perspectives in the ecology of rare marine bacteria, hitherto characterized by dormancy and episodic boom and bust, as envisioned by the seed-bank hypothesis. The effect of abiotic factors and phytoplankton composition on the dynamics of abundant and rare taxa have been also explored in this study, including taxa in the attached fraction (> 3 microns) in a selection of samples over the 3 years.