Award: OCE-1747511

Primary production in the ocean contributes about 50% of the global oxygen production, and is performed by a highly diverse assemblage of algae and bacteria (phytoplankton). Such diversity implies myriad different ways in which individual species or clades respond to and are controlled by environmental variables and interspecies interactions. Currently available methods to measure production and growth rates cannot distinguish among the components of the assemblage and usually involve significant perturbations to the sample due to the need to perform incubation experiments. The main goal of this project was to develop and test new DNA sequencing based methods (SBM) for determination of phytoplankton growth rate on a taxon-specific basis from a natural mixed assemblage without the need for incubations. We performed experiments on photosynthetic cyanobacteria in cultures and analyzed metagenomic data from public databases to investigate whether the SBM could be used to measure growth rate in natural samples. We showed that the SBM are capable of extracting clade specific information on DNA replication from cultures and mixed assemblages, but that those data cannot be interpreted in terms of absolute growth rates. This is an important finding because the SBM have great advantages in ease of use and thus are very attractive to researchers. Our work shows that they cannot be naively applied to complex assemblages in the ocean. This research was carried out partially by a graduate student and two undergraduate students at Princeton University, and resulted in their training in the laboratory and in computational sequence analysis. The SBM use bioinformatics to extract information from DNA sequence databases and through this work, we made contributions to the training of the next generation of biologists, to whom bioinformatics will be an essential research tool. Last Modified: 09/09/2021 Submitted by: Bess B Ward