Award: DEB-1233085

Synechococcus blooms occur regularly in temperate coastal environments, but bloom dynamics are controlled by an unknown mix of factors such as temperature, light, grazers, and phages. Blooms may have some secondary effects on other organisms such as fish through production of toxins. To better understand Synechococcus blooms we determined Synechococcus cell number at a California coastal site and the abundance of the grazer population. We used new DNA sequencing technologies to examine the diversity of Synechococcus and their potential grazers and other eukaryotic microbes in the ecosystem. We surprisingly found that mixotrophy is common at certain times, especially July and possibly January at the SIO pier. Mixotrophy is when apparent grazers are both consuming Synechococcus and also carrying out photosynthesis using chloroplasts. Our 18S rRNA sequence data are providing some evidence that these mixotrophs were dinoflagellates and possibly a green prasinophyte alga Tetraselmis. Overall we obtained the first "next generation" DNA sequencing survey of eukaryotes at the SIO pier, a site that has been analyzed by microscopy since the 1920s. We found that molecular sequence approaches reveal a much more diverse eukaryotic population than known before. We also see the presence of dinoflagellate parasites that could affect dinoflagellate, and indirectly, Synechococcus abundance. We also found evidence of dramatic changes in Synechococcus diversity in 2016, eg high abundance of a species not typically dominant at the SIO pier. This could be due to high water temperatures that affected the California coastal ecosystem, but in any case this is the first evidence of the effect of higher water temperature on the microbial community. This project resulted in the training of a post-doctoral fellow, a graduate student, and several undergraduates. The results were disseminated through conference presentations, publications, and outreach activities. Last Modified: 01/24/2018 Submitted by: Brian P Palenik