Unraveling the roles of bacterial populations during spring algal blooms

The relevance of marine algae is reflected in annually recurring, massive algae blooms at upwelling zones and continental shelfs in temperate latitudes. Since 2009 at Helgoland Roads the bacterial succession after the spring algae bloom is observed in a joint DFG project (University of Greifswald, MPI for Marine Microbiology, University of Bremen MARUM, and AWI Helgoland, MIMAS, POMPU). This bacterial succession could be linked to substrate availability and besides monitoring of biodiversity and physicochemical parameters it was established that algal primary production triggered a bloom of bacteria characterized by swift successions of dedicated taxa like Flavobacteriia and Gammaproteobacteria as the key players. Hence, the succession of taxonomically distinct clades constituted a succession of distinct gene function repertoires, which suggested that changes in substrate composition over the course of the algae bloom were the main forces shaping the bacterioplankton community.

While the succession of particular bacterial taxa is well studied, the mortality factors of individual clades are not thoroughly explored yet. Beside bottom-up control of population dynamics (supply of substrates) top-down control by lysis (or grazing) is one of the main sources for mortality of marine bacteria. This lysis by phages, which is poorly understood for bacterial key groups in the marine environment is of particular interest with regard to the spring bloom succession.

PACES: Topic 2 WP2