The goal of this project is to study genetic changes in sediment revived diatom populations subjected to human and climate induced environmental stress across evolutionary time. The diatom genus Chaetoceros is primarily marine and are important primary producers in the food web in freshwater and oceans. The distribution of Chaetoceros is correlated with salinity gradient and have been reported to adapt to changing environmental conditions. Populations of Chaetoceros muelleri resurrected from both recent and ancient resting spores in sediments from three time periods (present and ancient: ~1000 and ~7000 calendar years BP) will be established. The first reference genome of a Chaetoceros species, Chaetoceros muelleri will be sequenced and will be used as a back-bone for our wholegenome and population genomics analyses. We will resequence individuals from recent (present) and ancient (~1000 and ~7000 calendar years BP) sediments. From the resequenced genomes possible candidate genes with a high degree of polymorphism between the ancient and recent strains will be identified. The populations will then be phenotyped, and individual fitness in response to salinity and light conditions will be determined by growing the populations under high (~12-13) and low (~6-8) salinity and high and low light (200 and 50 pmol photons m”2 s”1), conditions. Growth rate, cell density, chlorophyll a content will be measured. This approach will help identify variation in specific genes that are correlated with phenotypic trait values, and in this way help us infer links between genotype and phenotype. The correlation between genotype and phenotype will be experimentally verified by generating transcriptomes for a subset of phenotyped individuals from different treatments. Populations exposed to high and low salinity, light and temperature conditions will be analyzed to confirm the correlation between genetic divergence due to environmental stress in specific loci. This research is important as it will provide insights into diatom evolution over long evolutionary time and also help us predict the evolutionary response of species to environmental changes. Furthermore, in this study we will be identifying genetic markers which can be used to detect the signals of environmental stress.