In this study, we have carried out a broad census of histone PTMs in Ectocarpus chromatin and have developed a method to evaluate the genome-wide distribution of specific marks. We show that modulation of the expression of sporophyte-biased genes during the life cycle is correlated with marked changes in the pattern of three histone PTMs. In contrast, the expression patterns of gametophyte-biased genes were not correlated with modifications to the histone PTMs assayed, suggesting that gametophyte-biased and sporophyte-biased gene expression are mediated by different epigenetic processes.