Abstract: The present invention relates to the production of a triacylglycerol oil that is produced from a Pythium species of alga. In one embodiment, the algal species contains at least about 20 weight percent total lipids and contains at least about 10 weight percent of its total fatty acids as eicosapentaenoic acid (EPA) and less than about 5 weight percent of its total fatty acids as arachidonic acid (ARA). In another embodiment, the present invention relates to various methods to produce eicosapentaenoic acid (EPA) from a Pythium species of algae. In particular, Pythium irregulare can be utilized as a viable production organism.