Marine algae are critically important to the health and well-being of the World Ocean. Not only do they form the base of the marine food web, they are also central players in the biogeochemical cycles of the ocean and the atmosphere. These organisms are amazingly diverse, occurring in 4 kingdom-level phylogenetic groupings and having body sizes spanning 7 orders of magnitude. Nevertheless, models suggest that the distribution of algal functional groups in the modern ocean is a straightforward function of light, nutrient availability, and temperature, all of which are likely to change significantly due to anthropogenic forcing in the coming decades. Attempts to predict how these changes might affect algal communities and the ecosystems they support are hampered by a lack of understanding of the pace of evolutionary adaptation in these populations. In this talk I will discuss the outstanding questions - how fast do mutations arise, how much do they effect algal fitness, and how will the dynamic ocean environment affect their dissemination in the population - and how these questions are being addressed by our lab and others using a combination of experimental evolution techniques and global ocean modeling.