Marine bacteria and phytoplankton comprise the bulk of microbial communities, form the base of the food web and drive biogeochemical cycling in the ocean. The identity and function of microbes in open ocean environments have been well described, however, beyond water quality monitoring surveys, comprehensive investigations of microbial dynamics in important coastal environments are underrepresented. Consequently, our understanding of bacterial and phytoplankton interactions in highly dynamic coastal habitats is severely lacking.
In order to address this knowledge gap we designed a high temporal resolution study to examine microbial communities from 2 Sydney beaches (1 frequently impacted by stormwater and sewage input and the other relatively pristine) weekly for 24 months. We focussed our analyses on tracking patterns in the diversity and structure of bacterial and phytoplankton populations over weekly and seasonal durations, and during and following multiple heavy rainfall and stormwater events. By employing a suite of molecular and statistical approaches to tease apart and identify key interactions between bacteria, phytoplankton and environmental factors, this investigation has revealed reoccurring patterns of microbial population successions and fluctuations driven by both environmental and microbial interactions.